On the high side of low

Sea ice extent near both poles was again below average, but higher than in recent years for most of the month. In the Arctic, seasonal sea ice loss began more slowly in May than in the recent years as air temperatures were closer to the 1981 to 2010 average. In the Antarctic, a slowdown in ice growth late in the month quickly brought sea ice extent levels close to record lows.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2022 was 12.88 million square kilometers (4.97 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for May 2022 was 12.88 million square kilometers (4.97 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Average Arctic sea ice extent for May 2022 was 12.88 million square kilometers (4.97 million square miles) (Figure 1). This was 410,000 square kilometers (158,000 square miles) below the 1981 to 2010 average, yet it was the highest May extent since 2013. As was the case for April, sea ice extent was slow to decline, losing only 1.28 million square kilometers (494,000 square miles) during the month. Ice loss in May occurred primarily in the Bering Sea, the Barents Sea, and within Baffin Bay and Davis Strait. However, several openings, or polynyas, in the pack ice have started to form, particularly within the eastern Beaufort Sea, the Chukchi Sea, the Laptev Sea, and around Franz Joseph Land in the northern Barents Sea. Ice also started to pull back from the shores of Russia in the Kara Sea. In Hudson Bay, the ice started to melt out in the south within James Bay and off of Southampton Island in the north. Overall, the daily sea ice extent tracked within the interdecile range (encompassing 90 percent of the 1981 to 2010 daily values) for much of the month. By the end of the month, extent was close to the sea ice extent observed in late May 2012.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 5, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of June 5, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. || Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for May 2022. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for May 2022. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Through May, sea ice extent was tracking above levels not seen since 2013. The relatively extensive ice cover for this time of year was largely the result of lower than average temperatures in Baffin Bay. Winds from the north also slowed the retreat of ice in the Bering and Barents Seas. Within the Arctic Ocean, air temperatures at the 925 mb level (about 2,500 feet above the surface) were near average over most of the region in May, and 1 to 5 degrees Celsius (2 to 9 degrees Fahrenheit) above the 1981 to 2010 average along the coast of the Kara and East Siberian Seas, the East Greenland Sea, and the Canadian Archipelago (Figure 2b). Areas where openings formed within the ice cover were dominated by off-shore ice motion, pushing ice poleward as well as toward Fram Strait. This offshore ice motion is largely driven by a pattern of low sea level pressure over Eurasia coupled with high pressure over the Pacific sector of the Arctic (Figure 2c).

May 2022 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2022 shows a decline of 2.5 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly May ice extent for 1979 to 2022 shows a decline of 2.5 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

May sea ice extent declined by 1.28 million square kilometers (494,000 square miles), or at a rate of 41,200 square kilometers (15,900 square miles) per day, which was slower than the 1981 to 2010 average. This resulted in an average May extent that ranked fourteenth lowest in the satellite record. The downward linear trend in May sea ice extent over the 44-year-satellite record is 33,700 square kilometers (13,000 square miles) per year, or 2.5 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, May has lost 450,000 square kilometers (174,000 square miles) of sea ice. This is equivalent to the size of the state of California.

Polynyas help kick-start seasonal ice loss

Figure 4. This NASA Worldview image from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on May 29, 2022 shows polynyas forming off the coast of Siberia. ||Credit: NASA|High-resolution image

Figure 4a. This NASA Worldview image from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on May 29, 2022 shows polynyas forming off the coast of Siberia.

Credit: NASA
High-resolution image

Figure 4b. This plot shows the relationship between averaged sea ice extent from July through October (in blue) and the regional average fire-favorable weather index (FFWI) over the western United States the following autumn and early winter (September to December, in red). ||Credit: Zou et al., 2021|High-resolution image

Figure 4b. This plot shows the relationship between averaged sea ice extent from July through October (in blue) and the regional average fire-favorable weather index (FFWI) over the western United States the following autumn and early winter (September to December, in red).

Credit: Zou et al., 2021
High-resolution image

Polynyas have begun to form, providing open water regions that strongly absorb the sun’s energy, warming the near-surface ocean mixed layer, and enhancing lateral ice melt from the sides. One of the larger polynyas is in the Laptev Sea to the west of the New Siberian Islands (Figure 4a). Despite the thin cloud cover, polynyas can be seen at the edge of the landfast ice, ice fastened to the coastline, to the west of the New Siberian Islands as well off the coast of the Taymyr Peninsula between the Kara and Laptev Seas.

A consequence of summer sea ice loss is that the ocean absorbs more of the sun’s energy. Before the ice can form again in the fall and winter, this heat has to be released back to the atmosphere. This is one of the reasons why the Arctic is warming more strongly than the global average, particularly in the fall season. Studies have suggested this amplified Arctic warming may be impacting weather systems at lower latitudes. One hypothesis is that the warm air released from the surface propagates up through the atmosphere and disrupts the polar vortex in the stratosphere. This can lead to cold air outbreaks, such as in February 2021 when cold Arctic air reached as far south as Texas, causing the failure of the power grid, billions of dollars in damage, and loss of lives. Proposed links between Arctic warming and mid-latitude weather nevertheless remain controversial and are far from settled.

Another recent study reveals a correlation between Arctic sea ice extent (averaged from July to October) and conditions favoring California wildfires after removing the long-term trend in both the sea ice and a regional fire-favorable weather conditions index. However, correlation is not causation. This study addresses the potential physical link by examining sensitivity simulations using low and high sea ice years and comparing the atmospheric conditions from climate model runs. The results suggest that during low sea ice minimum years there is tendency for low sea level air pressure over Alaska and high sea level pressure over the western United States. This results in dry and hot air flowing from the south and southwest over California, conditions favorable for wildfires there in the following autumn and early winter (Figure 4b).

Mapping volume of ice and snow over Antarctic sea ice proves difficult

Figure 5a. The graph above shows Antarctic sea ice extent as of June 5, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5a. The graph above shows Antarctic sea ice extent as of June 5, 2022, along with daily ice extent data for four previous years and the record high year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 5b. This image shows dual frequency Ku- and Ka-band radar (KuKa) deployed over Antarctic pancake sea ice. ||Credit: NASA|High-resolution image

Figure 5b. This image shows dual frequency Ku- and Ka-band radar (KuKa) deployed over Antarctic pancake sea ice.

Credit: Povl Abrahamsen
High-resolution image

As reported in a previous post, this year, Antarctic sea ice shrank to the lowest extent in the satellite record at 1.92 million square kilometers (741,000 square miles) on February 25. This event was set against the background of several low minimum extents since 2014. During the month of May, sea ice tracked slightly below the 1981 to 2010 reference period, until late in the month when sea ice autumn growth slowed significantly (Figure 5a). Stronger than average winds from the north and northeast in the Belligshausen and Amundsen Sea regions led to warm conditions near the sea ice edge, inhibiting growth. At month’s end, Antarctic sea ice extent was above only 1980, 1986, 2017, and 2019 in the 44-year record. Sea ice is particularly low in the Amundsen and Weddell Seas.

Reliable information on Antarctic sea ice thickness, important for gaining a fuller understanding of the Antarctic sea ice system, remains elusive. In the Arctic, sea ice thickness can be more accurately estimated using satellite altimeters. However, studies suggest that satellite altimeters may be over-estimating ice thickness compared to ship-based observations. This may be because of the way snow cover on the ice affects the measurements. There are still large uncertainties in the Antarctic snow and sea ice thickness, and hence the overall sea ice volume.

A United Kingdom-led project, called Drivers and Effects of Fluctuations in sea Ice in the ANTarctic (DEFIANT), aims to address this problem. The DEFIANT team is particularly interested in learning how radar waves interact with the snow that covers Antarctic sea ice. A recent DEFIANT field campaign involved three scientists travelling to the Weddell Sea with a radar designed to mimic those mounted on satellites. They investigated radar penetration into snow of different ages, densities, and surface roughness (Figure 5b). The results will help the research community better understand how to measure the underlying sea ice thickness using satellites. In 2023, two DEFIANT-affiliated scientists will spend the entire winter in Antarctica with the same radar instrument, monitoring the snow cover and its radar-reflective properties.

References

Zou, Y., P. J. Rasch, H. Wang, et al. 2021. Increasing large wildfires over the western United States linked to diminishing sea ice in the Arctic. Nature Communications. doi:10.1038/s41467-021-26232-9

Springtime in the Arctic

Arctic spring melt has begun. Ice extent declined most substantially in the Bering Sea and the Sea of Okhotsk. Overall decline was slower than average through the month.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2022 was 14.06 million square kilometers (5.43 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for April 2022 was 14.06 million square kilometers (5.43 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Average Arctic sea ice extent for April 2022 was 14.06 million square kilometers (5.43 million square miles) (Figure 1). This was 630,000 square kilometers (243,000 square miles) below the 1981 to 2010 average and ranked eleventh lowest in the 44-year satellite record. Extent declined slowly through the beginning of the month, with only 87,000 square kilometers (33,600 square miles) of ice loss between April 1 and April 10. The decline then proceeded at an average pace for this time of year through the reminder of the month. Reductions in sea ice extent during April occurred primarily in the Bering Sea and the Sea of Okhotsk. Other regions had small losses at most. The southern Barents Sea lost some ice, but the channel of open water north of Novaya Zemlya that persisted for much of the winter closed during April. Overall, the daily sea ice extent tracked just below the interdecile range (below 90 percent of past daily values) for the month.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of May 2, 2022, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of May 2, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for April 2022. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for April 2022. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2d. In April, strong offshore winds over the northwest coast of Alaska led to openings in the ice cover, called polynyas. This animation (click to see animation) shows the polynyas that formed in the Chukchi Sea from April 12 to 30, 2022. ||Credit: Agnieszka Gautier, National Snow and Ice Data Center|High-resolution image

Figure 2d. This animation (click to see animation) shows the polynyas, or openings in the ice cover, that formed in the Chukchi Sea from April 12 to 30, 2022. In April, strong offshore winds over the northwest coast of Alaska led to the formation of these polynyas. 

Credit: Agnieszka Gautier, National Snow and Ice Data Center
High-resolution image

During April, temperatures at the 925 mb level (about 2,500 feet above the surface) over the Arctic Ocean were above average. Most areas were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above average, but in the Beaufort Sea, April temperatures were up to 5 to 6 degrees Celsius (9 to 11 degrees Fahrenheit) above average (Figure 2b). This was accompanied by a strong Beaufort High pressure cell through the month (Figure 2c).

Strong offshore winds over the northwest coast of Alaska led to openings in the ice cover, called polynyas. The first pulse of winds began on March 21. At that time, surface air temperatures were still well below freezing, and the water in the coastal polynya quickly refroze. By April 9, the offshore push of the ice ceased and the polynya iced over completely. However, starting on April 12, a second round of offshore wind pushed the ice away from the coast, initiating another polynya. Refreezing began anew in the open water areas, but the ice growth was noticeably slower, reflecting the higher surface air temperatures by the end of the month (Figure 2d).

April 2022 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2022 shows a decline of X.X percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly April ice extent for 1979 to 2022 shows a decline of 2.6 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The downward linear trend in April sea ice extent over the 44-year-satellite record is 37,900 square kilometers (14,600 square miles) per year, or 2.6 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, April has lost 1.68 million square kilometers (649,000 square miles) of sea ice. This is equivalent to the size of the state of Alaska.

Sea ice age

Figure 4. This map shows the age of Arctic sea ice for the March 12 to 18 period in (a) 1985 and (b) 2022. The oldest ice, greater than 4 years old, is in red. Plot (c) shows the timeseries from 1985 through 2022 of percent cover of the Arctic Ocean domain (inset, purple region) by different sea ice ages during the March 12 to 18 period. ||Credit: M. Tschudi, W. Meier, and Stewart, NASA NSIDC DAAC| High-resolution image

Figure 4. This map shows the age of Arctic sea ice for the March 12 to 18 period in (a) 1985 and (b) 2022. The oldest ice, greater than 4 years old, is in red. Plot (c) shows the timeseries from 1985 through 2022 of percent cover of the Arctic Ocean domain (inset, purple region) by different sea ice ages during the March 12 to 18 period.

Credit: M. Tschudi, W. Meier, and Stewart, NASA NSIDC DAAC
High-resolution image

With the onset of spring, it is time again for a check-in on sea ice age—the number of years that a parcel of ice has survived summer melt. As noted in previous posts, ice age provides a qualitative assessment of thickness, as older ice has more chances to thicken through ridging, rafting, and bottom ice growth (accretion) during winter. The coverage of the old, thick ice has a significant control on how much total ice survives the summer melt season—the first-year ice that grows thermodynamically over winter is more easily melted away during summer. That which survives through the summer melt season grows in age by one year. The extent of old ice declines through the winter when it drifts out of the Arctic through the Fram or Nares Strait. At the end of last summer, the extent of the oldest ice (greater than 4 years old) tied with 2012 for the lowest in the satellite record. This spring, we continue to see a dominance of first-year ice (Figure 4). The percentage of the greater than 4-year-old ice, which once comprised over 30 percent of the Arctic Ocean, now makes up only 3.1 percent of the ice cover.

Bering Sea crabs

Figure 5. The fishing boat Pinnacle makes its way through a Bering Sea ice floe on January 25, 2022. Crab fishing is dangerous work due to frequently rough seas, icing conditions, and the threat of sea ice. Ice floes can damage buoys and increase the risk of a lost crab pot. ||Credit: Loren Holmes/Anchorage Daily News. |High-resolution image

Figure 5. The fishing boat Pinnacle travels through a Bering Sea ice floe on January 25, 2022. Crab fishing is dangerous work due to frequently rough seas, icing, and dense pack ice.

Credit: Loren Holmes/Anchorage Daily News.
High-resolution image

The Bering Sea is an important crab fishery, with several species represented. Crab fishing is dangerous work because of frequently rough seas, icing on the ship’s superstructure, and dense pack ice (Figure 5). This past winter, the population of lucrative snow crabs was down substantially. This decline in crabs appears to be related to low sea ice extent during the 2018 and 2019 winters. Snow crabs prefer cold bottom water that protects the young from predators. The cold-water pool on the Bering Sea floor is caused by winter ice formation where dense, cold, and salty water sinks as the ice grows. However, in 2018 and 2019 there was very little ice. This opened young crabs to more predation, and far fewer survived to maturity.

Antarctica rising

Figure 6. Antarctic sea ice extent for April 2022 was 5.84 million square kilometers (2.25 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 6. Antarctic sea ice extent for April 2022 was 5.84 million square kilometers (2.25 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

After the record low minimum Antarctic sea ice extent at the end of February and the strong heat wave that followed in mid-March, conditions in the Southern Ocean have calmed down. Ice extent remains low for this time of year below the interdecile range, but is above 2017, 2018, and 2019, as well as 1980. Extent remained below average in the Weddell, eastern Ross, and western Amundsen-Bellingshausen regions, but near average around the rest of the continent (Figure 6). Through April, ice extent increases in all regions around the continent, but with relatively slower growth in the Amundsen-Bellingshausen Seas.

First Multidisciplinary Drifting Observatory for the Study of Arctic Climate science team meeting

Figure 7. The first in-person Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) science conference was held at the end of April in Potsdam, Germany. This was the first chance to present findings from the year-long expedition and pave the way for future analysis and collaboration. ||Credit: Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition|High-resolution image

Figure 7. The first in-person Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) science conference was held at the end of April in Potsdam, Germany. This was the first chance to present findings from the year-long expedition and pave the way for future analysis and collaboration.

Credit: Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition
High-resolution image

The Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition took place during 2019 and 2020 when the German icebreaker, Polarstern, was frozen into the ice and drifted across the Arctic for nearly a year. During the year, numerous observations were taken of the atmosphere, ocean, sea ice, and biogeochemistry. The scientific analysis is ongoing, and exciting results are starting to be reported.

The first in-person MOSAiC science conference was held at the end of April in Potsdam, Germany (Figure 7). This was the first chance to present findings from the year-long expedition and pave the way for future analysis and collaboration. Science teams from each discipline (atmosphere, ocean, sea ice, snow, remote sensing, ecosystem, biogeochemistry) discussed initial research results. Key to the success of MOSAiC is the strong interdisciplinary collaboration of the projects needed to provide a holistic understanding of Arctic Ocean changes and their impacts. NSIDC scientist Julienne Stroeve presented on the impacts of a rain-on-snow event in mid-September and the potential impact this would have on satellite retrievals of sea ice concentration, snow depth, and ice thickness. In January 2023, all MOSAiC data collected will be made available to the wider science community.

David Barber

Figure 8. Polar scientist David Barber of the University of Manitoba passed away on April 15, 2022. ||Credit: University of Manitoba|High-resolution image

Figure 8. Polar scientist David Barber of the University of Manitoba passed away on April 15, 2022.

Credit: University of Manitoba
High-resolution image

It is with sadness that we note the passing of one of the world’s pre-eminent polar scientists, David Barber, of the University of Manitoba, who died on April 15, 2022. He was a force in Canadian science, leading several large projects that increased understanding of sea ice and the Arctic.

References

Bernton, H., and L. Holmes. 2022. A crab boat’s quest for snow crab in a Bering Sea upended by climate change. The Seattle Times. https://pulitzercenter.org/stories/crab-boats-quest-snow-crab-bering-sea-upended-climate-change

Rascoe, A. 2022. Snow crabs in the Bering Sea have been hard to find — partially due to climate change. National Public Radio. https://www.npr.org/2022/04/10/1091927681/snow-crabs-in-the-bering-sea-have-been-hard-to-find-partially-due-to-climate-cha.

Thoman, Jr., R. L., U .S. Bhatt, P. A. Bieniek, B. R. Brettschneider, M. Brubaker, S. L. Danielson, Z. Labe, R. Lader, W. N. Meier, G. Sheffield, and J. E. Walsh. 2020. The record low Bering Sea ice extent in 2018: Context, impacts, and an assessment of the role of anthropogenic climate change. Bulletin of the American Meteorological Society. doi:10.1175/BAMS-D-19-0175.1.

University of Manitoba. 2022. Mourning the loss of visionary Arctic researcher, Dr. David Barber. UM Today News. https://news.umanitoba.ca/mourning-the-loss-of-visionary-arctic-researcher-dr-david-barber/.

Sea ice age data sets from the NSIDC DAAC: Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1 and EASE-Grid Sea Ice Age, Version 4.

 

Arctic sea ice approaches maximum; record low minimum in the south

Arctic sea ice is approaching its seasonal peak, with below-average sea ice extent in the Barents Sea and the Sea of Okhotsk, but near-average ice extent elsewhere. Antarctic sea ice extent set a record low minimum for the satellite data era. However, two regions of high interest to researchers remained locked in ice: Thwaites Glacier and the central Weddell Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2022 was 14.61 million square kilometers (5.64 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1a. Arctic sea ice extent for February 2022 was 14.61 million square kilometers (5.64 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Figure 1b. The graph above shows Arctic sea ice extent as of March 7, 2022, along with daily ice extent data for four previous years and the record low year. 2021 to 2022 is shown in blue, 2020 to 2021 in green, 2019 to 2020 in orange, 2018 to 2019 in brown, 2017 to 2018 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1b. The graph above shows Arctic sea ice extent as of March 7, 2022, along with daily ice extent data for four previous years and the record low year. 2021 to 2022 is shown in blue, 2020 to 2021 in green, 2019 to 2020 in orange, 2018 to 2019 in brown, 2017 to 2018 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Average Arctic sea ice extent for February 2022 was 14.61 million square kilometers (5.64 million square miles), ranking fourteenth lowest in the satellite record. The 2022 extent was 690,000 square kilometers (266,000 square miles) below the 1981 to 2010 average. Through most of February, extent hovered near the interdecile range, roughly at the lowest 10 percent of the measured extents for those days. Regionally, the sea ice extent was near average in the Bering Sea but continued to be well below average in the Sea of Okhotsk. In the Barents Sea, extent was below average, and a narrow open-water area extended north of Novaya Zemlya. Extent also remained below average in the Gulf of St. Lawrence and along the eastern Greenland coast. As is generally the case near the maximum sea ice extent, there are ups and downs in extent associated with storms moving the ice around, melt along the southern ice margins, and subsequent regrowth.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for February 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for February 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for December 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for February 2022. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

In February 2022, temperatures at the 925 hPa level (about 2,500 feet above sea level) ranged from 1 to over 8 degrees Celsius (2 to 14 degrees Fahrenheit) above the 1981 to 2010 average along the Eurasian coast and across the central Arctic Ocean (Figure 2a). However, cool conditions prevailed over much of Canada and Baffin Bay; temperatures were generally 2 to 7 degrees Celsius (4 to 13 degrees Fahrenheit) below average. The sea level air pressure pattern in February was marked by strong low pressure centered over the North Atlantic and high pressure over central Asia, acting to drive air northward from Eastern Europe to the central Arctic, consistent with the above average temperatures there (Figure 2b). In North America, low pressure over the North Atlantic, extending over Baffin Bay, drew Arctic air southward over eastern Canada, bringing cool conditions to the area.

February 2022 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2022 shows a decline of 2.8 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly February ice extent for 1979 to 2022 shows a decline of 2.8 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The downward linear trend in February sea ice extent over the 44-year satellite record is 42,500 square kilometers (16,400 square miles) per year, or 2.8 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, February has seen a loss of 1.82 million square kilometers (703,000 square miles). This is equivalent to about seven times the area of Oregon.

Antarctic sea ice minimum sets a record

Figure 4a. Before 2022, the previous record low Antarctic sea ice extent was observed on March 3, 2017. This figure shows the difference in sea ice extent from that date (shown in white) compared with the new record low on February 25, 2022 (shown in dark blue). Ice present on both dates is shown in light blue. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 4a. Before 2022, the previous record low Antarctic sea ice extent was observed on March 3, 2017. This figure shows the difference in sea ice extent from that date (shown in white) compared with the new record low on February 25, 2022 (shown in dark blue). Ice present on both dates is shown in light blue.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 4b. This figure shows the pattern of the 2021 to 2022 Antarctic sea ice decline since the September winter maximum. Each panel shows the sea ice extent for the two dates in the legend, with the earlier date extent in white and the later date extent in light blue. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 4b. This figure shows the pattern of the 2021 to 2022 Antarctic sea ice decline since the September winter maximum. Each panel shows the sea ice extent for the two dates in the legend, with the earlier date extent in white and the later date extent in light blue.

Credit: National Snow and Ice Data Center
High-resolution image

In the south, Antarctic sea ice recently reached its late-summer minimum, dropping below all previous minimum ice extents in the satellite record (Figure 4a). For the first time since the satellite record began in 1979, extent fell below 2 million square kilometers (772,000 square miles), reaching a minimum extent of 1.92 million square kilometers (741,000 square miles) on February 25. Ice extent declined at a near-average rate through most of the month at about 40,000 square kilometers (15,400 square miles) per day, but the decline significantly slowed to about 15,000 square kilometers (5,800 square miles) per day towards the end of the month.

Following the unusually early and above average sea ice maximum extent on September 1, there was a rapid decline in ice extent through the austral spring and summer, with the most notable feature being the clearing out of ice from the Ross and Amundsen Sea sectors during January and February as well as the loss of ice from the northwestern Weddell Sea region during that period (Figure 4b). Much of the Antarctic coast is still ice-free and sea ice remains well below average in the eastern Ross Sea, western Bellingshausen Sea, and northwestern Weddell Sea. However, persistent patches of high concentration sea ice in the area of Pine Island Bay and in the central Weddell Sea are obstructing research groups trying to work in those areas. The RV Nathaniel B Palmer, operated by the National Science Foundation (NSF), and the RV Araon, operated by South Korea’s Korean Polar Research Institute (KOPRI), have been attempting to conduct research near the outlet of Thwaites Glacier. The research teams were forced to work at an adjacent region to the west, the Dotson Ice Shelf, to avoid the heavy ice conditions near Thwaites.

Ups and downs in the southern ice

Figure 5a. This plot shows the annual Antarctic minimum daily (5-day running average) extent for 1979 to 2022 (black) and the 1979 to 2022 trend line (blue). For the first time since the satellite record began in 1979, sea ice in the Southern Hemisphere fell below 2 million square kilometers (772,000 square miles), reaching a minimum of 1.92 million square kilometers (741,000 square miles) on February 25. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 5a. This plot shows the annual Antarctic minimum daily (5-day running average) extent for 1979 to 2022 (black) and the 1979 to 2022 trend line (blue). For the first time since the satellite record began in 1979, sea ice in the Southern Hemisphere fell below 2 million square kilometers (772,000 square miles), reaching a minimum of 1.92 million square kilometers (741,000 square miles) on February 25.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 5b. This plot shows the changes in the trend of seasonal sea ice minimums over the satellite record for Antarctic sea ice, beginning with the trend after ten years and proceeding year-by-year. For much of the satellite monitoring period, the trend has been towards increasing ice, but the vertical bars show that the high variability in the records means that the trend is not statistically significant. As of 2022, the net trend is very close to zero. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 5b. This plot shows the changes in the trend of seasonal sea ice minimums over the satellite record for Antarctic sea ice, beginning with the trend after ten years and proceeding year-by-year. For much of the satellite monitoring period, the trend has been towards increasing ice, but the vertical bars show that the high variability in the records means that the trend is not statistically significant. As of 2022, the net trend is very close to zero.

Credit: National Snow and Ice Data Center
High-resolution image

The Antarctic sea ice is notable for its variability, both seasonally, losing over 80 percent of its ice cover from its maximum to its annual minimum extent, and from year to year. While 2022 had a record low minimum, the highest minimum in the satellite record was observed as recently as 2015 (Figure 5a). The effect of this large year to year variability on computed trends is evident when plotting how the trend has changed over time (Figure 5b). We calculated the trend for the period of 1979 to 1988, then 1979 to 1989, then 1979 to 1990, and so forth.

The trend is initially positive for the 1979 to 1988 period, but then dips negative for a couple years, then bounces between positive and negative until the year 2001, after which it remained positive through 2021. Also plotted is the 2 standard deviation range of the trend as the vertical “whiskers” for each year; this is a measure of how confident one should be in the trend values. If the 2 standard deviation range for a computed trend crosses the zero line (i.e., encompasses both positive and negative values), it means that the trend value may simply be due to the year-to-year swings in the extent. Phrased differently, it means that the trend does not meet the 95 percent confidence level for statistical significance. So while the trend in minimum extent has been largely positive over the past two decades, it has not been significant except the three-year period, 2014 to 2016. Through 2022, the trend starting in 1979 is ever so slightly negative again: -18 square kilometers (-6.94 square miles) per year. But it is still not a significant trend. Variability in summer continues to rule Antarctic sea ice extent.

Eos recently published an article that summarizes three different modeling studies that attempt to explain the causes of the variability and the (until this year) positive trend in Antarctic sea ice extent. The article finds that while winds and sea surface temperature are important contributors to the growth of Antarctic sea ice over the last 30+ years, there are likely additional factors at play.

Search for the Endurance

Figure 6. Mrs. Chippy, the resident cat of Endurance, the vessel that carried Ernest Shackleton and his team to Antarctica in 1914, stands on the shoulder of a crewmember. Mrs. Chippy did not survive the expedition. ||Credit: Perce Blackborow| High-resolution image

Figure 6a. Mrs. Chippy, the resident cat of Endurance, the vessel that carried Ernest Shackleton and his team to Antarctica in 1914, stands on the shoulder of a crewmember. Mrs. Chippy did not survive the expedition.

Credit: Perce Blackborow
High-resolution image

Figure 6b. This image shows the stern of the Endurance, the ship used by Ernest Shackleton to reach the Weddell Sea on his ill-fated Imperial Trans-Antarctic Expedition. The ship was found in 3,000 meters (10,000 feet) of water in the northwestern Weddell Sea by a search expedition using uncrewed submersible vehicles. ||Credit: Falklands Maritime Heritage Trust and National Geographic. | High-resolution image

Figure 6b. These images show the stern of the Endurance, the ship used by Ernest Shackleton to reach the Weddell Sea on his ill-fated Imperial Trans-Antarctic Expedition. The ship was found in 3,000 meters (10,000 feet) of water in the northwestern Weddell Sea by a search expedition using uncrewed submersible vehicles.

Credit: Falklands Maritime Heritage Trust and National Geographic.
High-resolution image

In the Weddell Sea, the South African research icebreaker RV Agulhas II has been attempting to find the wreck of the Endurance on the seafloor. The Endurance is the vessel that brought Ernest Shackleton and his team to Antarctica in 1914, only to be blocked by sea ice. The ice later crushed the ship and the team was forced to trek across the sea ice and sail to a small, uninhabited island near the tip of the Antarctic Peninsula. Shackleton and five others then sailed in a lifeboat over 1,600 kilometers (1,000 miles) to South Georgia Island, one of the greatest polar voyages in history, to reach civilization. They then returned in a Chilean ship, the Yelcho, to rescue the rest of the expeditioners on Elephant Island. Miraculously, all of the human crew were successfully rescued. However, several sled dogs and one male cat, Mrs. Chippy, did not survive (Figure 6a).

On March 5, the Endurance was found by undersea drones operating from the South African ice breaker (Figure 6b). This was after just two weeks of searching in the area where the navigator of the 1915 expedition, Frank Worsely, noted its last location. It was found in 3,000 meters (10,000 feet) of water in near-pristine condition because of the absence of wood-boring worms in the Weddell benthic ecosystem. The ship was found just 6 kilometers (4 miles) from the last reported location, made on November 21, 1915, with sextant and chronometer.

Further reading

Alexander, C., and J. Dorman. 2003. The Endurance: Shackleton’s Legendary Antarctic Expedition. Columbia TriStar.

Amos, J. 2022. Endurance: Shackleton’s lost ship is found in Antarctic. BBChttps://www.bbc.com/news/science-environment-60662541

Blanchard-Wrigglesworth, E., I. Eisenman, S. Zhang, S. Sun, and A. Donohoe. 2022. New Perspectives on the Enigma of Expanding Antarctic Sea Ice. Eos.
https://eos.org/science-updates/new-perspectives-on-the-enigma-of-expanding-antarctic-sea-ice

Davidson, L. 2022. The Adventures of Mrs. Chippy, Shackleton’s Seafaring Cat. History Hit. https://www.historyhit.com/mrs-chippy-shackletons-seafaring-cat/

Sir Ernest Shackleton Endurance Expedition Trans-Antarctica 1914-1917 – 1, Departure. Cool Antarctica. https://www.coolantarctica.com/Antarctica%20fact%20file/History/Shackleton-Endurance-Trans-Antarctic_expedition.php

Worsley, F. A. 1998. Shackleton’s boat journey. WW Norton & Company.

Update

When we first published this post, the Endurance had not yet been found. We updated this post on March 9, 2022, to include the information about the discovery of the Endurance. 

A good winter, relatively speaking

By early January 2022, Arctic sea ice extent, while well below average, was within the lowest decile of recorded extents of the 1981 to 2010 reference period. Sea ice now completely covers Hudson Bay; the only area with substantially below average extent is in southern Baffin Bay and north of Labrador.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2021 was 13.48 million square kilometers (5.20 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for December 2021 was 12.19 million square kilometers (4.71 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Average Arctic sea ice extent for December 2021 was 12.19 million square kilometers (4.71 million square miles), which ranked thirteenth lowest in the satellite record. The 2021 extent was 650,000 square kilometers (251,000 square miles) below the 1981 to 2010 average. As of early January 2022, sea ice completely covers Hudson Bay. The only area with extent remarkably below normal is southern Baffin Bay and off the coast of Labrador, where the December sea ice extent ranked fourth lowest.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of January 4, 2022, along with daily ice extent data for four previous years and the record low year. 2021 to 2022 is shown in blue, 2020 to 2021 in green, 2019 to 2020 in orange, 2018 to 2019 in brown, 2017 to 2018 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of January 4, 2022, along with daily ice extent data for four previous years and the record low year. 2021 to 2022 is shown in blue, 2020 to 2021 in green, 2019 to 2020 in orange, 2018 to 2019 in brown, 2017 to 2018 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for December 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory |High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for December 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic at the 925 hPa level, in degrees Celsius, for December 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for December 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

The air temperature pattern averaged for December 2021 at the 925 millibar level (about 2,500 feet above the surface) was characterized by above average temperatures. Temperatures were up to 6 degrees Celsius (11 degrees Fahrenheit) above average over Greenland, north of the Canadian Arctic Archipelago, and the East Greenland Sea. Three areas of below average temperatures were found over western and eastern Eurasia and northwestern Canada (Figure 2b). The corresponding sea level pressure pattern for December 2021 featured fairly low pressures (less than 1,015 millibars) encompassing essentially all of the Arctic except for the Laptev Sea region (Figure 2c). These pressures were nevertheless not substantially unusual compared to average—at most 6 to 7 millibars below average. The notable exception is south of the Aleutian Islands, where the sea level pressure was up to 24 millibars above average.

December 2021 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2021 shows a decline of 3.1 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly December ice extent for 1979 to 2021 shows a decline of 3.5 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The downward linear trend in December sea ice extent over the 43-year satellite record is 45,000 square kilometers (17,400 square miles) per year, or 3.5 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, December has seen a loss of 1.88 million square kilometers (726,000 square miles). This is equivalent to about three times the size of Texas.

Hudson Bay ices over

Figure 4. This NASA Worldview image shows the last of the Hudson Bay freezing up along the southeast coast as of December 23, 2021. After a late freeze up, Hudson Bay is completely ice covered as of early January 2022. ||Credit: NASA| High-resolution image

Figure 4. This NASA Worldview image shows the last part of  Hudson Bay freezing up along the southeast coast as of December 23, 2021. After a late freeze up, Hudson Bay is completely ice covered as of early January 2022.

Credit: NASA
High-resolution image

In our previous post, we noted that by the end of November, the northern half of Hudson Bay is usually completely iced over. As of the end of November 2021, only the far north was frozen over; the rest of the bay was ice free except for a narrow band of ice along the western coastline. However, as lower temperatures kicked in and the upper ocean lost the heat that it had gained in summer, the entire bay subsequently froze over. The ice cover is now complete.

Antarctic notes

Figure 4. Antarctic sea ice extent for December 2021 was 9.2 million square kilometers (3.55 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5. Antarctic sea ice extent for December 2021 was 9.2 million square kilometers (3.55 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Antarctic sea ice extent for December 2021 was low overall, tracking at similar extents seen in 2017. Regionally, extent was particularly low in the Weddell Sea and southern Ross Sea regions. Several large polynyas formed in the eastern Weddell Sea; the Maud Rise Polynya opened in late November and then spread east to northeast. This is unusual; normally, the polynya extends south and west of its initiation point. The Southern Annular Mode (SAM) was in a strong positive phase through the first half of the month, indicating strong westerly winds and a strong low-pressure area in the Amundsen Sea. Sea ice conditions are not yet favorable for two planned cruises near Thwaites Glacier, one by the US Antarctic research program (RV Nathaniel B. Palmer) and the other by the South Korean (RV Araon). Ships are due to arrive in late January.

Killer whales in the Arctic

Bowhead whales have played an integral role in the cultural and subsistence life of Inuit communities for millennia. New research at the University of Washington analyzing acoustic data has found that the loss of sea ice has allowed killer whales, also known as Orcas, to venture into waters that were once inaccessible to them. The expanding range of killer whales, a top predator, has potential ramification for the Arctic food web and especially bowhead whales. Indigenous Arctic communities have noted an increased number of carcasses of bowhead whales in the Chukchi and Beaufort seas that were preyed upon by Orcas. Normally, bowheads can avoid predation by retreating into protective areas of heavy sea ice that the smaller Orcas cannot break through to breathe. If the bowheads must spend more time in thick ice, this can be a problem because feeding opportunities are more limited. Calves that cannot break through the ice may also drown.

Winter is settling in

The sea ice extent has been quickly growing, and by the end of October, ice covered most of the Arctic Ocean. Overall, the ice extent remained below average for this time of year in the Barents and Kara Seas, as well as within northern Baffin Bay and the East Greenland Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2021 was 6.77 million square kilometers (2.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for October 2021 was 6.77 million square kilometers (2.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

The monthly average extent for October 2021 was 6.77 million square kilometers (2.61 million square miles). This ranked eighth lowest in the long-term satellite data record, tied with 2017. It was 1.44 million square kilometers (556,000 square miles) greater than the record low of 5.33 million square kilometers (2.06 million square miles) recorded in 2020, and 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 long-term average. Ice growth was robust across the Eurasian side of the Arctic, including the East Greenland Sea, but there was little expansion of ice southwards within the eastern Beaufort Sea.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of November 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of November 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, from October 1 to 30, 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory |High-resolution image

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for October 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2c. This plot shows the departure from average sea level pressure in the Arctic at the 925 hPa level, in degrees Celsius, for October 2021. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory| High-resolution image

Figure 2c. This plot shows the departure from average sea level pressure in the Arctic at the 925 hPa level, in degrees Celsius, for October 2021. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

As of October 31, sea ice extent is tracking higher than any year since 2015, as well as higher than observed in 2007, 2011, and 2012 (Figure 2a).

Average monthly air temperatures were well below freezing across much of the Arctic Ocean in October, the exceptions being along the coastal regions of the Barents Sea and across the North Atlantic region. Nevertheless, air temperatures at the 925 hPa level (about 2,500 feet above the surface) were above the 1981 to 2010 average, up to 8 degrees Celsius (14 degrees Fahrenheit) above average north of Greenland and the Canadian Archipelago (Figure 2b).

Above average temperatures were related in part to unusually low sea level pressure extending from Siberia across to Alaska, coupled with above average sea level pressure northeast of Greenland extending down towards Baffin Bay. In particular, the strong sea level pressure gradient between the low and high sea level pressure near the Canadian Arctic Archipelago helped to funnel winds from the south over Baffin Bay, which is still ice-free, northwards towards the central Arctic Ocean (Figure 2c).

Overall, ice extent increased by 99,700 square kilometers (38,500 square miles) per day during the month of October. This rate of increase was larger than the 1981 to 2010 average of 89,200 square kilometers (34,400 square miles) per day.

October 2021 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2021 shows a decline of 9.8 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly October ice extent for 1979 to 2021 shows a decline of 9.8 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The downward linear trend in October sea ice extent over the satellite record is 82,100 square kilometers (31,700 square miles) per year, or 9.8 percent per decade relative to the 1981 to 2010 average (Figure 3). While percentagewise, the overall long-term trend is largest in September, the actual amount (based on the linear trend) of ice lost per year is larger in October: 82,100 square kilometers (31,700 square miles) versus 81,200 square kilometers (31,400 square miles) in September.

Overall, since 1979, October has lost 3.45 million square kilometers (1.33 million square miles) of ice, based on the linear trend. This is equivalent to twice the size of the state of Alaska.

Last ice refuge continues to show signs of weakness

Figure 4. This NASA Moderate Resolution Imaging Spectroradiometer (MODIS) image from May 20, 2020, shows a large polynya, or open water region, that formed north of Ellesmere Island in Canada. ||Credit: NASA| High-resolution image

Figure 4. This NASA Moderate Resolution Imaging Spectroradiometer (MODIS) image from May 20, 2020, shows a large polynya, or open water region, that formed north of Ellesmere Island in Canada.

Credit: NASA
High-resolution image

In February 2018, a large polynya (open water region) formed northeast of Greenland. In May 2020, another large polynya formed north of Ellesmere Island (Figure 4). This region contains the oldest and thickest ice in the Arctic Ocean, a result of the Beaufort Gyre circulation, which pushes the ice towards the coasts of Greenland and the Canadian Archipelago, where it compresses along the coasts. However, during the polynya formation events, winds helped to push the ice away from the shores, leaving open water for several days. While such events have occurred before, they are rare. However, as the ice cover continues to thin, the ice will become more vulnerable to disruption by winds that can form such polynyas and seaward ridging and rafting of the ice.

Seeing daylight in the Antarctic

Figure 5. The graph above shows Antarctic sea ice extent as of November 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5. The graph above shows Antarctic sea ice extent as of November 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Since the Antarctic maximum sea ice extent was reached on September 1, 2021, ice extent has been in a steep decline. Extent went from being above the interdecile (ninetieth percentile) range to being below the tenth percentile for most of October. As a result, sea ice extent in the Antarctic is currently tracking as the third lowest, behind only 2016 and 1986. Sea ice extent is particularly low along the western side of the Antarctic Peninsula, including the northern Weddell Sea and the central Indian Ocean sector. Air temperatures at the 925 hPa level (about 2,500 feet above the surface) were up to 6 degrees Celsius (11 degrees Fahrenheit) above average within the Weddell Sea. A strong low pressure feature in the Amundsen Sea and above average air pressure in the area south of Australia drove winds that led to the pattern of sea ice extent around the continent.

References

Moore, G. W. K., S. E. L. Howell, and M. Brady. 2021. First observations of a transient polynya in the Last Ice Area north of Ellesmere Island. Geophysical Research Letters. doi: 10.1029/2021GL095099

 

An odd summer’s end

The Arctic sea ice minimum extent is imminent. After a cool and stormy summer, this year’s minimum extent will be one of the highest of the past decade, despite the amount of multiyear ice standing at a near-record low. A large area of low ice concentration persists in the Beaufort and Chukchi Seas, and some of this may still be compacted by winds or melt away because of the remaining heat in the upper ocean.

Overview of Conditions

Figure 1a. Arctic sea ice extent for September 15, 2021 was 4.73 million square kilometers (1.83 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1a. Arctic sea ice extent for September 15, 2021 was 4.73 million square kilometers (1.83 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Figure 1b. This map shows Arctic sea ice concentration based on data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) data as of September 14, 2021. Yellows indicate sea ice concentration of 75 percent, dark purples indicate sea ice concentration of 100 percent. ||Credit: University of Bremen|High-resolution image

Figure 1b. This map shows Arctic sea ice concentration based on data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) data as of September 14, 2021. Yellows indicate sea ice concentration of 75 percent; dark purples indicate sea ice concentration of 100 percent.

Credit: University of Bremen
High-resolution image

As of September 15, Arctic sea ice extent stood at 4.73 million square kilometers (1.83 million square miles), placing it tenth lowest in the satellite record for the date. While extent continues to decline as of this post, the seasonal minimum is likely to occur soon, depending on how much heat remains in the upper ocean and on winds, which can compact the ice cover or spread it out. If the winds push the ice poleward, this may further reduce the total extent. Nevertheless, the seasonal minimum extent promises to be one of the highest of the past decade—only 2013, 2014, and 2018 are currently tracking above the 2021 sea ice extent.

It has been an odd summer. While fairly cool and stormy summer conditions limited summer melt, as discussed in our earlier post, the amount of multiyear ice is at a record low, roughly one-fourth of the amount seen in the early 1980s. Ice loss the first two weeks of September primarily occurred in the Beaufort and Chukchi Seas, and to a lesser extent also surrounding Severnaya Zemlya. As seen in Advanced Microwave Scanning Radiometer 2 (AMSR-2) imagery (Figure 1b), areas of low concentration ice persist in the Beaufort and Chukchi Seas; how much of this ice melts away largely depends on ocean heat. Satellite mapping of sea surface temperatures shows much of the open ocean surrounding the low ice concentration area is already near the freezing point. By contrast, the compact, well-defined ice edge along most of the Russian side of the Arctic Ocean indicates that freezing is already underway in this area.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, between September 1 to 13, 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, between September 1 to 13, 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from September 1 to 13, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from September 1 to 13, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Air temperatures at the 925 hPa level (about 2,500 feet above the surface) as assessed over the first 13 days of September were near average over most of the Arctic Ocean. Temperatures from 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average were the rule along the coasts of the Kara and Laptev Seas (Figure 2a). In sharp contrast to the persistent pattern of low pressure over the Arctic Ocean characterizing this summer, the first 13 days of September saw high average air pressure (Figure 2b).

Focus on the Northwest Passage

Figure 3. These graphs show the total sea ice area along each Northwest Passage route (y axis) by day (x axis) dating back to 1981. The top graph shows the northern route and the bottom graph shows the southern route. As of early to mid-September, the northern deep-water route is choked with ice and will not open this year; ice conditions are quite severe compared to the past couple of decades. By contrast, there is much less ice in the southern route (approximately 30,000 square kilometers or 11,600 square miles) and as noted, most of this is located on Somerset and Prince of Wales Islands. On the other side of the Arctic, the Northern Sea Route is essentially open, though some areas of ice remain near Severnaya Zemlya. ||Credit: XX|High-resolution image

Figure 3. These graphs show the total sea ice area along each Northwest Passage route (y axis) by day (x axis) dating back to 1981. The top graph shows the northern route and the bottom graph shows the southern route. 

Credit: Canadian Ice Service
High-resolution image

Data from the Canadian Ice Service compiled by colleague Steve Howell of Environment and Climate Change Canada allows for a closer look at sea ice conditions in the Northwest Passage. While there are multiple Northwest Passage routes, most attention is focused on the southern route, known as Amundsen’s route, entered from the Pacific side through Amundsen Gulf, and the northern route entered from the Pacific side via M’Clure Strait. This wide, deeper-water route is the one that might become a viable waterway for commercial shipping in the future. As of early to mid-September, the northern deep-water route is choked with ice and will not open this year; ice conditions are quite severe compared to the past couple of decades. By contrast, there is much less ice in the southern route, approximately 30,000 square kilometers (11,600 square miles). Most of this is located on Somerset and Prince of Wales Islands. On the other side of the Arctic, the Northern Sea Route is essentially open, though some areas of ice remain near Severnaya Zemlya.

Antarctic oddities

Figure 4. Antarctic sea ice extent for September 15, 2021 was 18.64 million square kilometers (7.20 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4. Antarctic sea ice extent for September 15, 2021 was 18.64 million square kilometers (7.20 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Antarctic sea ice extent is approaching its seasonal maximum, which typically occurs in late September. A surge in sea ice growth or outward transport in late August in the northeastern Weddell Sea and the area north of Dronning Maud Land brought sea ice extent to the fifth-highest level for the last day of the month. Since then, losses in the areas around the tip of the Antarctic Peninsula and the northeastern Ross Sea have reduced the total ice extent, although at this time of year, ice extent can change rapidly up or down as storms play havoc with thin, low concentration ice in the extended ice edge regions. As of this post, Antarctic ice extent remains well above the long-term average.

Beaufort breakup

Arctic sea ice extent declined more slowly during August 2021 than most years in the past decade, and as a result, this year’s September minimum extent will likely be among the highest since 2007. Part of the reason for this is a persistent low pressure area in the Beaufort Sea, which tends to disperse ice and keep temperatures low. A remaining question is whether a large area of low concentration ice north of Alaska will melt away. Antarctic sea ice is nearing its seasonal maximum, and the monthly mean extent for August was the fifth highest in the satellite record.

Overview of conditions

Figure 1a. The graph above shows Arctic sea ice extent as of September, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1a. The graph above shows Arctic sea ice extent as of September 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 1b. This map shows Arctic sea ice concentration based on data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) data as of August 28, 2021. Yellows indicate sea ice concentration of 75 percent, dark purples indicate sea ice concentration of 100 percent. ||Credit: University of Bremen|High-resolution image

Figure 1b. This map shows Arctic sea ice concentration based on data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) data as of August 28, 2021. Yellows indicate sea ice concentration of 75 percent, dark purples indicate sea ice concentration of 100 percent.

Credit: University of Bremen
High-resolution image

Figure 1c. Arctic sea ice extent for August 2021 was 5.75 million square kilometers (2.22 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1c. Arctic sea ice extent for August 2021 was 5.75 million square kilometers (2.22 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

The decline in sea ice extent during August was relatively slow but steady after a pause in ice loss around August 9. The average daily loss was 33,000 square kilometers (12,700 square miles) per day, although by the end of the month the pace of ice loss increased to 51,000 square kilometers (19,700 square miles) per day as areas within the Beaufort and Chukchi Sea started to lose more ice. The monthly average extent for August 2021 is 5.75 million square kilometers (2.22 million square miles) (Figure 1a). This is 1.03 million square kilometers (398,000 square miles) above the record low for the month set in 2012 and 1.45 million square kilometers (560,000 square miles) below the 1981 to 2010 average. The average extent for the month ranks tenth lowest in the passive microwave satellite record.

By the end of the month, large areas of the Beaufort and Chukchi Seas were covered by low concentration ice (25 to 75 percent; Figure 1b); some of this ice may yet melt away or fall below the 15 percent concentration threshold adopted for calculating ice extent. Many other areas have unusually low extent, such as Fram Strait and north of Svalbard and Franz Josef Land. As noted in our July post, open water persists north of Greenland in the Wandel Sea, an area that has rarely been open in past years. A small area of ice persists in the eastern Kara Sea (Figure 1c). At this time of year, any remaining sea ice loss is primarily driven by melt from heat absorbed in the ocean mixed layer. Compaction from northward winds may also reduce ice extent.

Conditions in context

Figure 2. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, between August 1 to 30, 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, between August 1 to 30, 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

A pair of monthly-averaged high and low air pressure regions governed the weather in the high Arctic in August, centered in the northernmost Laptev and the central Beaufort Seas, respectively. These patterns created strong winds from the north over the Alaska and Bering Sea region, leading to temperatures at the 925 hPa level (approximately 2,500 feet above the surface) that were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below the 1981 to 2010 average. Warm conditions prevailed over northern Siberia; temperatures there were as much as 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) above average. A persistent area of low pressure between Hudson Bay and Baffin Island drove winds from the south over Greenland, which were responsible for several above-average temperature events in Greenland during the month.

August 2021 compared to previous years

Figure 3. Monthly August ice extent for 1979 to 2021 shows a decline of 10.4 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly August ice extent for 1979 to 2021 shows a decline of 10.4 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

The pace of ice loss for the month was much slower than in recent years but still near the average pace for the reference period of 1981 to 2010, leading to the tenth lowest August of the satellite data record. Through 2021, the linear rate of decline for monthly mean August sea ice extent is 10.4 percent per decade (Figure 3). This corresponds to 75,000 square kilometers (29,000 square miles) per year. The cumulative August ice loss over the 43-year satellite record is 3.15 million square kilometers (1.22 million square miles), based on the difference in linear trend values in 2021 and 1979. The loss of ice since 1979 in August is equivalent to about twice the size of the state of Alaska.

Buoy oh buoy

Figure 4. This graph shows data from one ice mass balance (IMB) monitoring buoy in the Chukchi Sea off the northwest coast of Alaska from April through August. The data demonstrate that bottom ice growth continued into May. Surface snow melt started in June, and by July, bottom melt began. Surface freeze-up occurred in early August while bottom melt continued through mid-August. ||Credit: The Cold Regions Research and Engineering Laboratory-Dartmouth Mass Balance Buoy Program| High-resolution image >

Figure 4. This graph shows data from one ice mass balance (IMB) monitoring buoy in the Chukchi Sea off the northwest coast of Alaska from April through August. The data demonstrate that bottom ice growth continued into May. Surface snow melt started in June, and by July, bottom melt began. Surface freeze-up occurred in early August while bottom melt continued through mid-August.

Credit: The Cold Regions Research and Engineering Laboratory-Dartmouth Mass Balance Buoy Program
High-resolution image >

Ice mass balance (IMB) monitoring buoys drifting in the Arctic Ocean provide data on both surface melting and sub-surface thinning of the ice by warm ocean water. The IMB buoys include a downward-looking acoustic sounder above the ice to obtain snow depth on sea ice, temperature sensors (thermistor string) through the ice, and an upward-looking underwater acoustic sensor to measure the depth of the bottom of the ice. Putting these measurements together provides a profile of ice thickness and snow depth. Real-time data are provided, but are subject to errors. Data are later corrected to provide a high-quality climate record.

New buoys are regularly deployed to replace those that have ceased operation or have drifted out of the Arctic Ocean into the Atlantic. Data from one buoy in the Chukchi Sea off the northwest coast of Alaska is shown in Figure 4 for April through August. The data demonstrate that bottom ice growth continued into May. Surface snow melt started in June, and by July, bottom melt began in earnest. Surface freeze-up occurred in early August while bottom melt continued through mid-August. This is typical for sea ice—ocean heat continues to melt ice from the bottom (and sides) even as the surface air temperatures drop below 0 degrees Celsius (32 degrees Fahrenheit) and the top of the ice cover begins to refreeze. Overall, the ice thickness dropped from about 1.5 meters (4.9 feet) in late June to about 0.5 meters (1.6 feet). As of the end of August, thickening of the ice through bottom freezing has begun.

Northern passages

Figure 5. In this image, a Coast Guard Cutter HEALY crewmember prepares to retrieve an oceanographic research mooring in the Chukchi Sea on August 2, 2021. ||Credit: Janessa Warschkow, U.S. Coast Guard| High-resolution image

Figure 5. In this image, a Coast Guard Cutter HEALY crewmember prepares to retrieve an oceanographic research mooring in the Chukchi Sea on August 2, 2021.

Credit: Janessa Warschkow, U.S. Coast Guard
High-resolution image

A persistent tongue of ice has remained along the coast of the Severnya Zemlya islands. However, ice has pulled away from the Siberian coast, opening a narrow channel with little or no ice. Regardless of the ice, there have been icebreaker-supported transits through the passage through the summer. And in fact, there was even a winter transit in January through February.

The Northwest Passage (NWP) through the channels of the Canadian Archipelago still has ice blocking all routes, although concentration and extent are low in some areas. Nevertheless, this past week, the U.S. Coast Guard icebreaker, the Healy, left port in Seward, Alaska, to begin a transit through the NWP. The mission is focused on conducting scientific research, including mapping of the seafloor and providing experience in navigating through the passage.

Icebergs in the Arctic Ocean

Figure 6. These images from Planet image data, show the break-up of the Milne Ice Shelf located in northern Ellesmere Island; the large pieces seen in the 31 July image are now adrift in the Beaufort, and are much thicker that multi-year sea ice. The Canadian Ice Service is tracking the larger pieces. ||Credit: Planet, and Chris Shuman| High-resolution image

Figure 6. These images from Planet image data show the break-up of the Milne Ice Shelf located in northern Ellesmere Island; the large pieces seen in the 31 July image are now drifting in the Beaufort, and are much thicker than multi-year sea ice. The large iceberg labeled “Arctic ‘ice Island'” is about 10 kilometers by 8 kilometers in size. The Canadian Ice Service is tracking the larger pieces.

Credit: Planet, and Chris Shuman
High-resolution image

The break up of the Milne Ice Shelf in June 2020 spawned several tabular icebergs that are now drifting in the Arctic Ocean (Figure 6). While not unprecedented, these ‘ice islands,’ as they were called in the 1950s, are now quite rare. The icebergs are a result of the calving retreat and demise of several small Arctic-style ice shelves (much smaller than Antarctic ice shelves) that formerly occupied several of the fjords along the northern coast of Ellesmere Island. Calving and loss of most of the Milne Ice Shelf (the setting for a work of fiction, “Deception Point” by Dan Brown) in late July 2020 marked the break-up of the last relatively intact ice shelf of a fringe of shelves that once spanned several thousand square kilometers along the Ellesmere coast. The Canadian Ice Service is tracking the bergs.

Antarctic Notes

Figure 7. The graph above shows Antarctic sea ice extent as of September 1, 2021, along with daily ice extent data for four previous years and the record high year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 7. The graph above shows Antarctic sea ice extent as of September 1, 2021, along with daily ice extent data for four previous years and the record high year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Sea ice in the Southern Ocean surrounding Antarctica was well above the 1981 to 2010 average extent in August, rising above the ninetieth percentile of the satellite record period near the end of the month (Figure 7). As of this post, Antarctic sea ice extent is fifth highest for the day in the satellite record, a sharp contrast from the several years of persistent below-average ice extent following an abrupt change in September 2016. Antarctica’s sea ice is highly variable. Sea ice extent is slightly above average in nearly all sectors, in particular in the Weddell and Cosmonaut Seas and the region north of eastern Wilkes Land.

Further Reading

Crary, A. P., R. D. Cotell, and T. F. Sexton. 1952. Preliminary Report on Scientific Work on “Fletcher’s Ice Island.” Arctic5(4), pp.211-223.

Koenig, L. S., K. R. Greenaway, M. Dunbar, and G. Hattersley-Smith. 1952. Arctic ice islands. Arctic5(2), pp.66-103.

Brown, D. 2001. Deception Point, Simon and Schuster, 372 pp.

A change of pace

The rate of Arctic sea ice loss was somewhat slow through much of July, lowering prospects for a new record low minimum extent in September. The month as a whole was marked by widespread low pressure over most of the Arctic Ocean, which was much more extensive than recorded for June.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2021 was 7.69 million square kilometers (2.97 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for July 2021 was 7.69 million square kilometers (2.97 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

The seasonal decline in Arctic sea ice extent was fairly rapid during the first week of July, but slowed later in the month. The monthly average extent for July 2021 was 7.69 million square kilometers (2.97 million square miles). This was 400,000 square kilometers (154,000 square miles) above the record low for the month set in 2020 and 1.78 million square kilometers (687,000 square miles) below the 1981 to 2010 average. The average extent for the month ranks fourth lowest in the passive microwave satellite record. The rapid ice loss in the Laptev Sea early in the melt season has slowed, but extent in the Laptev remains well below average. Ice extent in the Beaufort and Chukchi Seas continues to be near the long-term average.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 2, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2015 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of August 2, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from July 1 to 31, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from July 1 to 31, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Figure 2c. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for July 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 2c. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for July 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

At the start of July, sea ice extent was above the levels recorded in 2012, the year that ended up with the lowest September ice extent in the satellite record. However, fairly rapid ice loss during the first week of July brought extent below 2012 levels. From July 4 to July 9, the 2021 extent was the lowest in the satellite record for that time of the year. However, the loss rate then slowed, and by late July, 2021 extent was tracking above 2020, 2019, 2011, and 2007 (Figure 2a). Overall, sea ice extent decreased by 2.96 million square kilometers (1.14 million square miles) during July 2021. This corresponds to an average loss of 95,300 square kilometers (36,800 square miles) per day, slightly faster than the 1981 to 2010 July average daily loss.

Low pressure continued to dominate the Arctic Ocean region in July, becoming more widespread than in June, with some indications that the pattern was breaking down late in the month. Monthly mean sea level pressures were below 1,004 millibars over most of the Arctic Ocean (Figure 2b). The low pressure brought generally cloudy conditions. Air temperatures at the 925-millibar level (about 2,500 feet above the surface) were within about two degrees Celsius (4 degrees Fahrenheit) of average over nearly all of the Arctic Ocean (Figure 2c).

July 2021 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2021 shows a decline of 7.5 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly July ice extent for 1979 to 2021 shows a decline of 7.5 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

Through 2021, the linear rate of decline for July sea ice extent is 7.5 percent per decade. This corresponds to 70,500 square kilometers (27,200 square miles) per year. The cumulative July ice loss over the 43-year satellite record is 2.96 million square kilometers (1.14 million square miles) based on the difference in linear trend values in 2021 and 1979. The loss of ice in July since 1979 is equivalent to about ten times the size of Arizona.

Northern routes across the Arctic

Figure 4. This image shows potential navigational routes through the Arctic from Mudryk et al., 2021. ||Credit: Mudryk et al., 2021. | High-resolution image

Figure 4. This image shows potential navigational routes through the Arctic from Mudryk et al., 2021.

Credit: Mudryk et al., 2021.
High-resolution image

In recent years, the trans-Arctic Northern Sea Route corridor along the Russian coast has become ice free, or nearly so, in summer, with significant commercial shipping transport (in general, with icebreaker escort). Things are looking different this year. While sea ice receded from the coast in the Laptev Sea several weeks ago, the Kara Sea coastline still remains locked in ice. In the Eastern Siberian Sea, ice remains near the coast. Whether these areas will clear of ice by the end of summer remains to be seen.

The southern route of the Northwest Passage through the channels of the Canadian Archipelago (Figure 4) is still locked in ice and seems unlikely to open in any significant way this year. However, more open summer conditions are likely in the future as temperatures continue to increase, according to a recent study in Nature Climate Change. Led by Lawrence Mudryk at Environment and Climate Change Canada, the study examines ice conditions under future warming scenarios. Based on climate model projections, the authors found that under 2 degrees Celsius (4 degrees Fahrenheit) of global warming, the target of the Paris Agreement, there is a 100 percent probability that the Northwest Passage will be navigable for at least some period by the end of summer. A caveat is that the current climate models do not necessarily capture processes that result in thick ice piling up due to winds and currents pushing ice from the Arctic Ocean into the archipelago’s channels.

Rising in the south

Figure 5. Antarctic sea ice extent for July 2021 was 16.38 million square kilometers (6.32 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5. Antarctic sea ice extent for July 2021 was 16.38 million square kilometers (6.32 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

In the Antarctic, sea ice extent increased faster than average during July, particularly in the latter half of the month. By the end of the month, extent was above the ninetieth percentile and was eighth highest in the satellite record. Extent was higher than average in the northeastern Ross Sea and in the Southern Ocean south of Africa, extending north from the coast of Dronning Maud Land and Enderby Land. Sea ice was below average in the area west of the Peninsula (the Bellingshausen Sea). Through 2021, the linear rate of increase for July sea ice extent is 0.6 percent per decade, but the uncertainty on this trend is ±0.7 percent. While this corresponds to 9,000 square kilometers (3,500 square miles) per year, the low level of certainty on the trend means that no clear pattern has yet emerged for Southern Ocean sea ice.

Further reading

Mudryk, L. R., J. Dawson, S. E. L. Howell, C. Derksen, T. A. Zagon, and M. Brady. 2021. Impact of 1, 2 and 4 °C of global warming on ship navigation in the Canadian Arctic. Nature Climate Change. doi:10.1038/s41558-021-01087-6.

Storms were the norm

A stormy May over the eastern Arctic helped to spread the sea ice pack out and keep temperatures relatively mild for this time of year. As a result, the decline in ice extent was slow. By the end of the month, several prominent polynyas formed, notably north of the New Siberian Islands and east of Severnaya Zemlya.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2021 was 12.66 million square kilometers (4.89 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for May 2021 was 12.66 million square kilometers (4.89 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent continued the slow pace of seasonal decline observed in April, leading to an average extent for May 2021 of 12.66 million square kilometers (4.89 million square miles). This was 740,000 square kilometers (286,000 square miles) above the record low for the month set in 2016 and 630,000 square kilometers (243,000 square miles) below the 1981 to 2010 average. The average extent for the month ranks ninth lowest in the passive microwave satellite record. The ice edge is near its average location most everywhere in the Arctic Ocean except in the Labrador Sea and east of Novaya Zemlya. Nevertheless, large polynyas have formed, notably north of the New Siberian Islands and east of Severnaya Zemlya. Open water areas have also developed near the coast in the southern Beaufort Sea and west of Utqiaġvik, Alaska (formerly Barrow). Overall, ice retreat during May occurred primarily in the Bering and Barents Seas, the Sea of Okhotsk and within the Laptev Sea.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2015 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of June 7, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars on May 12, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars on May 12, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars on May 24, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars on May 24, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2d. This plot shows average sea level pressure in the Arctic in millibars for May 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2d. This plot shows average sea level pressure in the Arctic in millibars for May 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Figure 2e. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 2e. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

The slow pace of sea ice loss this month (Figure 2a) can be explained in large part by a series of storms that migrated over the pole during May. The first storm split from a system over the Barents Sea and then slowly intensified over the central Arctic Ocean before reaching peak intensity (1007 hPa) north of Severnaya Zemlya on May 4. This was followed by another storm tracking northward from Europe, reaching peak intensity (sea level pressure of 987 hPa) over Severnaya Zemlya on May 12 and then joining with another storm that formed over Siberia on May 16 (Figure 2b). The strongest of the storms in terms of minimum central pressure (984 hPa) pressure, achieved on May 24, once again was located over Severnaya Zemlya and resulted from the merging of two systems moving in from the Barents Sea (Figure 2c).

As a result of the May storms, sea level pressure was lower than average by 6hPa centered just south of the pole at about 90 degrees E longitude. This was coupled with sea level pressure of 6 to 8 hPa above average over Greenland and the Canadian Arctic Archipelago extending into the northern Beaufort and Chukchi Seas (Figure 2d). Combined, this sea level pressure pattern fostered cold air spilling out of the Arctic Ocean into the North Atlantic and warm air flowing from the south over eastern Russia, leading to monthly averaged air temperatures at the 925 hPa level 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above average for this time of year over much of the Arctic Ocean, but up to 6 degrees Celsius (11 degrees Fahrenheit) above average along the coast of the Laptev and East Siberian Seas (Figure 2e). By contrast, temperatures were below average east of Greenland and around Svalbard. Wind patterns also explain the opening of the ice cover around Franz Joseph Land, the New Siberian Islands, and in the southern Beaufort Sea.

May 2021 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2021 shows a decline of 2.7 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly May ice extent for 1979 to 2021 shows a decline of 2.7 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

Overall, the pace of ice loss was slower than average, leading to only the ninth lowest May extent during the satellite data record. Through 2021, the linear rate of decline for May sea ice extent, relative to the 1981 to 2020 average extent, is 2.7 percent per decade. This corresponds to 35,400 square kilometers (13,700 square miles) per year, about the size of the state of Maine. The cumulative May ice loss over the 43-year satellite record is 1.49 million square kilometers (575,000 square miles), based on the difference in linear trend values in 2021 and 1979. This is roughly twice the size of the state of Texas.

Capturing the break up in the Beaufort Sea

Visible wavelength imagery from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) provides the opportunity to track the ice breaking up in the southern Beaufort Sea this May; cloud cover was limited, offering decent views of the surface. Between April 25 and May 17, the pack ice started to move away from the landfast ice still attached to the coast, leading to open water and subsequent break up of the ice floes and partial break up of the landfast ice by mid-May. During the past winter, unusually high sea level pressure over the central Arctic Ocean resulted in unusually strong anticyclonic (clockwise) ice motion that drove a lot of fairly old ice from the central Arctic Ocean into the Beaufort Sea. Early break up of ice can enhance lateral and basal melt (at the underside of the ice) of the ice floes. This process can weaken the multiyear ice in the region and help to further deplete the Arctic of its multiyear ice. Large losses of multiyear ice in the region followed the unusually strong negative Arctic Oscillation winter of 2009 to 2010, which also featured a strong clockwise flow of the ice cover. More recently, analysis of Canadian ice charts by David Babb at the University of Manitoba suggests that between 2016 and 2020 on average 210,000 square kilometers (81,000 square miles) of multiyear ice now melts out each summer in the Beaufort Sea.

Are wavy jet stream winds wavier? Or not?

A new study takes a close look at an idea discussed several times in the Arctic Sea Ice News and Analysis (ASINA) reports—that Arctic Amplification, the observed strong warming in the Arctic region, driven in part by loss of Arctic sea ice, is affecting the shape and persistence of the jet stream. The polar front jet stream marks the boundary in the atmosphere between cold Arctic air and warmer mid-latitude air. Numerous studies have proposed that Arctic Amplification weakens the latitudinal temperature and atmospheric pressure gradient, manifested as a weaker and more sinuous jet stream. Since storms (low pressure systems) tend to form along the jet stream, weather in middle latitudes ought to become more variable, with large swings and more persistent patterns.

While the issue has long been controversial, the new study by James Screen, which was presented at the European Geophysical Union annual meeting in April, but has not yet been published, finds little evidence for this effect in climate model simulations and observations. In examining the past decade of observations, relationships that initially gave support to the idea have weakened. Even with far more open water conditions expected by 2050, the modeled effects of Arctic warming on the weather patterns at lower latitudes appear to be minor. The response is further obscured by the possibility of increased snowfall on Arctic land areas, creating cold regions that are not centered on the Pole. A separate new study by Jonathan Martin shows the polar jet has become slightly wavier and moved northward a bit, but maximum speeds in the jet are unchanged. The scientific debate on this issue is certain to continue.

Arctic sea ice thinning faster than expected

Figure 4. This plot shows mean sea ice thickness in the Beaufort, Chukchi, East Siberian, Laptev, Kara, and Barents seas in April 2021 from the Envisat and CryoSat-2 radar altimeters, processed with the conventional snow product (modified Warren (1999) or mW99) and a new, dynamic snow product (from SnowModel-LG). The rate of decline is more than doubled when processed with SnowModel-LG, as the sea ice thickness inferred from snow cover diminishes. ||Credit: R. Mallett. | High-resolution image

Figure 4. This plot shows average sea ice thickness in the Beaufort, Chukchi, East Siberian, Laptev, Kara, and Barents Seas in April 2004 to 2018 from the Environmental Satellite (Envisat) and CryoSat-2 radar altimeters, processed with the conventional snow product (modified Warren (1999) or mW99) and a new, dynamic snow product (from SnowModel-LG). The rate of decline is more than doubled when processed with SnowModel-LG, as the sea ice thickness inferred from snow cover diminishes.

Credit: R. Mallett, University College London.
High-resolution image

Satellites do not directly measure the thickness of sea ice. They measure the height of the ice surface above the ocean, termed the ice freeboard in the case of radar altimetry, or they measure the height of the ice plus the snow cover, in the case of laser altimetry. To convert these freeboards into total ice thickness requires knowledge of the depth and density of the snow cover atop the ice. Typically, a snow climatology based on snow depth observations collected several decades ago over multiyear ice is used. However, today’s Arctic mostly consists of smoother first-year ice, which tends to have a shallower snow pack than multiyear ice, allowing for deep snow accumulation around ridges. Further, delays in freeze-up and earlier melt onset in today’s warmer climate have reduced the time over which snow can accumulate on the ice. Both factors have resulted in a thinner snowpack than measured 20 years ago.

A new study published in The Cryosphere reveals that when using temporally varying snow depth and density estimates to convert ice freeboard to ice thickness, the ice is thinning at a faster rate in the Arctic marginal seas than previously believed (Figure 4). The time-varying snow depth is from a new data product, the SnowModel-LG, which is soon to be published at the NSIDC Distributed Active Archive Center (DAAC). It is based on coupling a sophisticated snow model with meteorological forcing data from atmospheric reanalysis systems and satellite-derived ice motion vectors. The study found that the rate of decline in ice thickness in the Laptev, Kara, and Chukchi seas was 70, 98 and, 110 percent faster, respectively, compared to previous estimates. As expected, the sea ice thickness variability also increased in response to interannually varying snow depth.

Antarctic notes

Figure 5a. The graph above shows Antarctic sea ice extent as of June 1, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2015 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5a. The graph above shows Antarctic sea ice extent as of June 7, 2021, along with daily ice extent data for four previous years and the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 5b. air temp as difference from average in Antarctic for May 2021||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory|High-resolution image

Figure 5b. This plot shows the departure from average air temperature in the Antarctic at the 925 hPa level, in degrees Celsius, for May 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
High-resolution image

Antarctic sea ice extent grew at a slightly below-average pace in May, moving the overall extent from slightly above average to tracking the 43-year satellite record daily-extent average line (technically, the ‘median’ line) quite closely (Figure 5a). Sea ice extent was below average in the Weddell and Ross Seas, and slightly above average in the Bellingshausen and Amundsen Seas. In keeping with the sea ice trends, air temperatures for the month were well above average over the west-central Weddell Sea, about 7 degrees Celsius (13 degrees Fahrenheit) above average for the month (Figure 5b).

An embayment, or notch, in the ice edge in the eastern Weddell suggests that the processes that create the Maud Rise polynya were active, but at month’s end, the sea ice edge in that area (near 0 degree longitude and 68 degrees S latitude) had not enclosed the potential polynya region.

Further reading

Liston, G. E., P. Itkin, J. Stroeve, M. Tschudi and J. S. Stewart. 2020. A Lagrangian snow-evolution system for sea-ice applications (SnowModel-LG): part I–model description. Journal of Geophysical Research.-Oceans. doi:10.1029/2019JC015913.

Mallett, R. D. C., J. C. Stroeve, M. Tsamados, J. C. Landy, R. Willatt, V. Nandan and G. E. Liston. 2021. Faster decline and higher variability in the sea ice thickness of the marginal Arctic seas. The Cryosphere. doi:10.5194/tc-15-2429-2021.

Martin, J. E. 2021. Recent trends in the waviness of the Northern Hemisphere wintertime polar and subtropical jets. Journal of Geophysical Research-Atmospheres. doi:10.1029/2020JD033668.

Stroeve, J. C., J. Maslanik, M. C. Serreze, I. Rigor and W. Meier. 2011. Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010. Geophysical Research Letters. doi: 10.1029/2010GL045662.

Stroeve, J., G. Liston, S. Buzzard, L. Zhou, R. Mallett, A. Barrett, M. Tsamados, M. Tschudi, P. Itkin and J. S. Stewart. 2020. A Lagrangian snow-evolution system for sea ice applications (SnowModel-LG): part II–analyses. Journal of Geophysical Research-Oceans. doi:10.1029/2019JC015900.

Warren, S. G., I. Rigor, N. Untersteiner, V. Radionov, N. Bryazgin, Y. Aleksandrov and R. Colony. 1999. Snow depth on Arctic sea ice. AMS Journey of Climate. doi:10.1175/1520-0442.

A step in our spring

The spring decline in Arctic sea ice extent continued at varying rates through the month of April, highlighted by a mid-month pause. Above average air temperatures and low sea level pressure dominated on the Atlantic side of the Arctic, while near average conditions ruled elsewhere.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2021 was 13.84 million square kilometers (5.34 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for April 2021 was 13.84 million square kilometers (5.34 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Arctic sea ice extent averaged for April 2021 was 13.84 million square kilometers (5.34 million square miles). This was 410,000 square kilometers (158,000 square miles) above the record low for the month set in 2019 and 850,000 square kilometers (328,000 square miles) below the 1981 to 2010 average. The average extent for the month ranks sixth lowest in the passive microwave satellite record. Extent was notably low in the Barents and Bering Seas as well as the Labrador Sea. Elsewhere, extent was close to or somewhat below average (Figure 1). The largest ice loss during April was in the Sea of Okhotsk and the Labrador Sea, with smaller losses along the southern edge of the Bering Sea, and in the eastern Barents Sea near the coast of Novaya Zemlya.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of May 4, 2021, along with daily ice extent data for four previous years and 2012, the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of May 4, 2021, along with daily ice extent data for four previous years and 2012, the record low year. 2021 is shown in blue, 2020 in green, 2019 in orange, 2018 in brown, 2017 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from April 14 to 19, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars from April 14 to 19, 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for April 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure. || Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars for April 2021. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.


Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Figure 2d. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 2d. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2021. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Sea ice extent remained below the tenth percentile range throughout the month of April. However, rate of decline was variable. Notably, the decline paused, and extent even slightly increased between April 14 and April 19 (Figure 2a). This was largely because of an increase in sea ice in the northern Barents Sea, particularly off the northwest coast of Novaya Zemlya.

This temporary ice expansion appears to have been primarily driven by low sea level pressure centered over the Laptev Sea (Figure 2b). This led to winds from the north in the northern Barents Sea, pushing ice southward. The sea level pressure pattern for the full month featured low pressure centered in the Barents Sea, north of the Scandinavian coast (Figure 2c); bringing warm winds from the south and above average monthly temperatures in the region. Elsewhere in the Arctic, conditions were more moderate with 925 mb temperatures 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) above average and weak high pressure (Figure 2d).

April 2021 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2021 shows a decline of 2.6 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly April ice extent for 1979 to 2021 shows a decline of 2.6 percent per decade.

Credit: National Snow and Ice Data Center
High-resolution image

Through 2021, the linear rate of decline for April sea ice extent, relative to the 1981 to 2010 average extent, is 2.6 percent per decade (Figure 3). This corresponds to 38,600 square kilometers (14,900 square miles) per year, about the size of the US states of New Hampshire and Connecticut combined. The cumulative April ice loss over the 43-year satellite record is 1.62 million square kilometers (625,000 square miles), based on the difference in linear trend values in 2021 and 1979, which is equivalent in size to 2.3 times the size of the state of Texas.

Sea ice age update

Figure 4. Sea ice age map for March 12 to 18 (a) 1985 and (b) 2021; (c) the 1985 to 2021 time series of percent coverage of the Arctic Ocean domain (inset map, purple shaded region). ||Credit: W. Meier, National Snow and Ice Data Center| High-resolution image

Figure 4. This figure compares sea ice age between March 12 to 18 for the years 1985 (a) and 2021 (b). The bottom graph (c) shows a time series from 1985 to 2021 of percent ice coverage of the Arctic Ocean domain. The Arctic Ocean domain is depicted in the inset map with purple shading. 

Credit: M. Tschudi, University of Colorado, and W. Meier and J.S. Stewart, National Snow and Ice Data Center/Image by W. Meier
High-resolution image

The sea ice continues to be far younger, and thus thinner, than in the 1980s. There is little change in the age distribution from last year. At the end of the ice growth season in mid-March, 73.3 percent of the Arctic Ocean domain was covered by first-year ice, while 3.5 percent was covered by ice 4+ years old. This compares to 70.6 percent and 4.4 percent respectively in March 2020. In March 1985, near the beginning of the ice age record, the Arctic Ocean region was comprised of nearly equal amounts of first-year ice (39.3 percent) and 4+ year-old ice (30.6 percent).

In 2021, the extremely high sea level pressure in February over the central Arctic Ocean produced a strong Beaufort Gyre sea ice circulation, as noted in our March post. This pushed a substantial amount of ice, including older ice, onto the northern Alaskan and Canadian coast in the Beaufort Sea. Some of this ice has now moved north and west into the Chukchi Sea–an isolated patch of older ice amidst first-year ice. This will bear watching through the summer to see the fate of that older ice.

Antarctica

Figure 5: Antarctic sea ice extent for April 2021 was 7.08 million square kilometers (2.73million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5: Antarctic sea ice extent for April 2021 was 7.08 million square kilometers (2.73million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

In the Antarctic, autumn is now in full swing, but ice growth has been somewhat sluggish through the month. At the beginning of the month, extent was between the seventy-fifth and ninetieth percentile range of the 1981 to 2010 climatology. By the end of the month, extent was within the inner quartile range and just above the median.

Antarctic extent for April 2021 was 7.08 million square kilometers (2.73 million square miles), 230,000 square kilometers (88,800 square miles) above the 1981 to 2010 average (Figure 5). Extent was low in the northwestern Weddell Sea region and northern Ross Sea, and both areas had temperatures 3 to 8 degrees Celsius (5 to 14 degrees Fahrenheit) above the reference period. Sea ice extent was generally above average elsewhere, particularly in the Amundsen Sea, where rather cool conditions prevailed for April, at 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average.

Seasonal predictability of Arctic sea ice from ocean heat transport

Figure 6. This figure shows correlations between ocean heat transport through the Bering strait and sea ice concentration in the Arctic Ocean. Heat transport anomalies in May are compared to June (left) and July (right) sea ice concentration anomalies. Red areas show regions of the Arctic Ocean where Pacific Ocean heat has the strongest influence on sea ice conditions. Significant correlations at the 95 percent significance level are outlined in black. Regions where the interannual variability in monthly sea ice concentration is larger than 10 percent are outlined in green. An anomaly refers to the deviation of ocean heat transports and sea ice concentrations from their linear trends. ||Credit: image adapted from Lenetsky et al. (2021). | High-resolution image

Figure 6. This figure shows correlations between ocean heat transport through the Bering strait and sea ice concentration in the Arctic Ocean. Heat transport anomalies in May are compared to June (left) and July (right) sea ice concentration anomalies. Red areas show regions of the Arctic Ocean where Pacific Ocean heat has the strongest influence on sea ice conditions. Significant correlations at the 95 percent significance level are outlined in black. Regions where the interannual variability in monthly sea ice concentration is larger than 10 percent are outlined in green. An anomaly refers to the deviation of ocean heat transports and sea ice concentrations from their linear trends.


Credit: image adapted from Lenetsky et al. (2021).
High-resolution image

As the Arctic summer nears, the Sea Ice Prediction Network team, which includes NSIDC scientists, is gearing up for another year of the Sea Ice Outlook. Participants in the Outlook and other researchers are investigating ways to better understand and improve seasonal predictability of Arctic September sea ice extent. One factor in sea ice predictability is ocean heat.

A recent study led by University of Colorado master’s student Jed Lenetsky, in collaboration with researchers at McGill University and the Massachusetts Institute of Technology, examined the influence of Pacific Ocean heat on sea ice conditions. Results show that Pacific Ocean heat entering the Arctic Ocean through the Bering Strait has the largest influence on sea ice conditions in the spring and early summer in the Chukchi Sea, fostering early opening of the pack ice and triggering the ice-albedo feedback (Figure 6). From August through October, the summer stratification of the Chukchi Sea reduces the influence of Pacific Ocean heat on sea ice conditions. At the same time, other processes, such as ocean heat uptake and wind-induced sea ice drift, become the dominant drivers of sea ice variability in the region. The influence of the Bering Strait heat transport re-emerges in November as a factor in the timing of freeze onset. These results have important implications for seasonal sea ice prediction in the Chukchi Sea, as predictions using Pacific Ocean heat are more skillful than predictions using more commonly used parameters such as sea ice concentration and sea ice thickness.

Further reading

Lenetsky, J. E., B. Tremblay, C. Brunette, and G. Meneghello. 2021. Subseasonal predictability of Arctic Ocean sea ice conditions: Bering Strait and Ekman-driven ocean heat transport.  J. Climate. doi:10.1175/JCLI-D-20-0544.1.