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 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

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 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

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 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 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 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. 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. BBC. https://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. 

While January began with sea ice extent below average, by the end of the month, extent increased. January 2022 finished as the sixteenth lowest extent in the satellite record above all years since 2009. This illustrates the large natural variability in sea ice conditions. However, winter ice extent is a poor indicator of what the ice extent will look like this coming September.

Overview of conditions

Figure 1a. Arctic sea ice extent for January 2022 was 13.88 million square kilometers (5.36 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 February 2, 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 January 2022 was 13.88 million square kilometers (5.36 million square miles), ranking sixteenth lowest in the satellite record (Figure 1a). The 2022 extent was 540,000 square kilometers (208,000 square miles) below the 1981 to 2010 average. Throughout most of January, extent tracked within the interdecile range of the satellite record, falling below the interdecile range on January 26 (Figure 1b). Regionally, the sea ice extent was above average in the Bering Sea, yet below average in the Sea of Okhotsk and the Barents Sea. Extent also remained lower than average in the Gulf of St. Lawrence. At the end of the month, sea ice extent was above all years since 2009.

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 January 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 sea level pressure in the Arctic in millibars for January 2022. 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

Air temperatures for January 2022 at the 925 millibar level (about 2,500 feet above the surface) were above average over all of the Arctic Ocean. Temperatures were up to 7 degrees Celsius (13 degrees Fahrenheit) higher than average north of the Canadian Archipelago, with more modest departures in other areas (Figure 2a). The corresponding sea level pressure pattern for January 2022 featured the characteristic Siberian high pressure region that typically forms over eastern Siberia in autumn and winter. However, sea level pressure was up to 8 millibars above average over eastern Siberia, stretching across the Bering Sea and into western Alaska (Figure 2b). This was coupled with below average sea level pressure over Eurasia and Hudson Bay. Generally, when the Siberian High is strong, advection of warm air from eastern Europe leads to mild conditions over the Kara and Laptev Seas. The high over Siberia was also complemented by low pressure south of the Aleutians. This pattern led to winds bringing cold air that enhanced freezing in the Bering Sea and pushed ice southward, leading to the higher extent in the Bering Sea.

January 2022 compared to previous years

Figure 3. Monthly January ice extent for 1979 to 2022 shows a decline of 3.0 percent per decade.

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

The downward linear trend in January sea ice extent over the 44-year satellite record is 42,800 square kilometers (16,500 square miles) per year, or 3.0 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, January has seen a loss of 1.86 million square kilometers (718,000 square miles). This is equivalent to about four times the area of California.

Role of North Atlantic Heat Transport on Barents Sea ice

Figure 4a. The left map of the Arctic Ocean shows the simulated average transport of water volume in Sverdrups (Sv: equal to one million cubic meters per second, or about 260 million gallons per second). The right map show the heat loss in terawatts (TW; equal to one trillion watts) for individual regions. The values shown are average annual values for 1900 to 2000.

Credit: Smedsrud et al. 2022
High-resolution image

Figure 4b. Annual ocean temperatures averaged between 50 and 200 meters (164 and 656 feet) depth from 1977 through 2020 showing the variation of ocean heat in the western Barents Sea.

Credit: Institute of Marine Research, Norway
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The northward flow of warm Atlantic Water along the coast of Norway is a primary oceanic heat source for the Arctic Ocean (Figure 4a). During periods when there is increased transport of Atlantic Water, there is reduced winter sea ice in northern Barents Sea and increased ocean heat loss, leading to denser water. The northward flow of Atlantic water towards the Arctic has been high in recent decades. According to colleagues at the Geophysical Institute in Bergen, Norway, the oceanic heat transport to the Arctic Ocean is 30 percent higher today than it was around 1900.  However, over a shorter time-frame, there is no distinct trend in warm water flow between 1995 and 2020. The total annual transport of ocean heat, a combination of water volume and the temperature of that water, started to decrease after 2015 (Figure 4b). However, while the volume of Atlantic Water through the Barents Sea opening started to drop in 2015, northern Norway experienced several strong storms from the south, that may have broken up the ice cover or kept it from advancing southward. The wind-driven changes in northward movement of Atlantic Water is likely a result of natural climate variability, including both upstream ocean circulation changes and large-scale atmospheric circulation patterns such as the Arctic Oscillation; however, some researchers think that sea ice loss in the Arctic may also be affecting wind patterns.

Antarctic sea ice taking the plunge

Figure 5a. The graph above shows Antarctic sea ice extent as of February 2, 2022, along with daily ice extent data for five previous years. 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 2013 to 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
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Figure 5b. These graphs show Antarctic sea ice extent in square kilometers in five different regions as well as Antarctica’s overall sea ice extent.

Credit: Robbie Mallet, University College London
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During the southern hemisphere spring in 2016, Antarctic sea ice suddenly shrank, leading to a series of months (extending into the 2016 to 2017 austral summer) with the lowest monthly average extents in the satellite data record. This January, Antarctic sea ice was the second lowest ice extent in the 44-year record (Figure 5a). Regionally, ice extent is tracking below levels observed for 2017 in the Indian and Pacific sectors, but above levels for that year in other sectors (Figure 5b). In 2017, only the Ross Sea region had record low extent, so it was the driver of the overall record low hemispheric extent. Similarly, this year none of the individual regions have record low extents, but all are well below average leading to the second lowest Antarctic sea ice in the satellite record, above 2017.

The more moderate extent levels since the record lows in 2016 to 2017 result in a small, not statistically significant (at the 95 percent level) positive trend. Climate models simulating the response to anthropogenic greenhouse gas emissions suggest that Antarctic sea ice should be decreasing. So there is a seeming contradiction between the observations and the models. One possibility is that natural variability is higher than the models indicate and that natural variability may still dominate the Antarctic sea ice trends. A new study led by R. Fogt looked at an ensemble of reconstructions of Antarctic sea ice extent since 1905 using sea level pressure, air temperatures, and indices of climate variability. This study argues that the seasonally observed positive trends since 1979 are unusual over the twentieth century, and that a shift occurred around 1960, before routine satellite observations began. This hints that there is indeed pronounced decadal scale variability in ocean and atmospheric conditions that influence Antarctic sea ice. Whether the low ice conditions of recent years represent a new decadal-scale shift remains to be seen.

References

Årthun, M., T. Eldevik, and L. H. Smedsrud. 2019. The Role of Atlantic Heat Transport in Future Arctic Winter Sea Ice Loss, Journal of Climate, 32(11), 3327-3341. Retrieved Feb 3, 2022, from https://journals.ametsoc.org/view/journals/clim/32/11/jcli-d-18-0750.1.xml.

Fogt, R.L., A. M. Sleinkofer, M. N. Raphael, et al. 2022. A regime shift in seasonal total Antarctic sea ice extent in the twentieth century. Nature Climate Chang. 12, 54–62. doi:10.1038/s41558-021-01254-9.

Helland-Hansen, B. and F. Nansen. 1909. The Norwegian Sea: Its physical oceanography based upon the Norwegian researches 1900–1904. Det Mallingske bogtrykkeri.

Orvik, K. A. 2022. Long-term moored current and temperature measurements of the Atlantic inflow into the Nordic Seas in the Norwegian Atlantic Current; 1995-2020. Geophysical Research Letters, 49, e2021GL096427. doi:10.1029/2021GL096427

Smedsrud, L. H., M. Muilwijk, A. Brakstad, E. Madonna, S. K. Lauvset, C. Spensberger, C., et al. 2022. Nordic Seas heat loss, Atlantic inflow, and Arctic sea ice cover over the last century. Reviews of Geophysics, 60, e2020RG000725. doi:10.1029/2020RG000725.

Erratum

On February 9, 2022, a user informed the ASINA team of an error in the text, which stated, “January 2022 finished as the sixteenth lowest extent in the satellite record above all years since 2009, with the exception of 2013 and 2014.” The correct text should state that “January 2022 finished as the sixteenth lowest extent in the satellite record above all years since 2009.” The correction has been made.

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 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 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 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 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 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 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.

Sea ice extent increased at a faster than average pace through November and by the end of the month, extent was just within the interdecile range. Extent was above average in the Bering Sea, but Hudson Bay remained unusually ice free through the month.

Overview of conditions

Figure 1. Arctic sea ice extent for November 2021 was 9.77 million square kilometers (3.77 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 November 2021 monthly average extent was 9.77 million square kilometers (3.77 million square miles), which ranked tenth lowest in the satellite record. The 2021 extent was 930,000 square kilometers (359,000 square miles) below the 1981 to 2010 long-term average. Extent was higher than average in the Bering Sea, but is extremely low in Hudson Bay.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of December 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, for November 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 in millibars for November 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 millibar level (about 2,500 feet above the surface) were well above average north of the Canadian Archipelago, by as much as 6 degrees Celsius (11 degrees Fahrenheit). Conversely, temperatures over southwest Alaska and the eastern sector of the Bering Sea were as much as 6 degrees Celsius (11 degrees Fahrenheit) below average (Figure 2b).

The sea level pressure pattern for November featured widespread low pressure over the Atlantic side of the Arctic and extending into the Barents and Kara Seas, paired with a moderately strong Beaufort Sea High (Figure 2c). Strong low pressure over the Gulf of Alaska resulted in a circulation pattern in the eastern Bering Sea that brought cold air from the north. This pattern was favorable for sea ice growth, and can explain the above average ice extent in the region.

November 2021 compared to previous years

Figure 3. Monthly November ice extent for 1979 to 2021 shows a decline of 5.0 percent per decade.

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

The downward linear trend in November sea ice extent over the 43-year satellite record is 53,300 square kilometers (20,600 square miles) per year, or 5 percent per decade relative to the 1981 to 2010 average. Also based on the linear trend, since 1979, November has lost 2.2 million square kilometers (849,000 square miles). This is equivalent to about three times the size of Texas.

No freeze in Hudson Bay

Figure 4. This map of Hudson Bay shows sea ice extent as of November 30, 2021. The US National Ice Center/NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) product provides the data for this map.

Credit: US National Ice Center and National Snow and Ice Data Center
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Typically, Hudson Bay begins freezing up by the beginning of November. By the end of the month, the northern half of the bay is usually completely iced over. However, as of the end of November 2021, only the far north has frozen over; the rest of the bay is ice free except for a narrow band of ice along the western coastline. According to the NSIDC Sea Ice Index, this is the second lowest extent in Hudson Bay at this time, above only 2010.

The USNIC/NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) product provides a more detailed view (Figure 4). It also shows ice only in the far north of the region and along the western coast. The lack of ice has potential ramifications for polar bears in the region that must wait for the bay to freeze over to hunt. While the lack of ice in Hudson Bay at this time of year is extreme, the bay will eventually freeze over through the coming winter.

Frozen in the Northern Sea Route

An early freeze of sea-ice has led to logistical chaos on the Northern Sea Route.

Credit: Rosatomflot via The Independent Barents Observer
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The story on the opposite side of the Arctic stands in sharp contrast to Hudson Bay. Ice formed along the eastern part of the Siberian coast relatively early, at least compared to recent years. This caught ships transiting through the Northern Sea Route by surprise. Several have become frozen in and are awaiting icebreakers to free them. In addition to the surprisingly early freeze up, winds also pushed ice together into ridges (piled up ice) that are much more difficult to navigate through. Supplies to northern Siberian cities have been delayed.

Springtime in the South

Figure 5. This maps shows Antarctic sea ice concentration on December 1, 2021. The yellow area shows missing data. 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
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In the Antarctic, ice extent declined relatively rapidly during the austral spring. By the end of November, extent was the second lowest in the satellite record, bested only by the extreme low recorded in 2016. Extent was particularly low in the Bellingshausen and Weddell Seas as well as in the Indian Ocean sector, north of Enderby Land. The Maud Rise polynya has once again formed. This feature was not seen for many years after the 1970s, but has started to form in recent years.

ASINA team member Ted Scambos is currently on his way to Antarctica for field work.

Reference

US National Ice Center and National Snow and Ice Data Center. Compiled by F. Fetterer, M. Savoie, S. Helfrich, and P. Clemente-Colón. 2010, updated daily. Multisensor Analyzed Sea Ice Extent – Northern Hemisphere (MASIE-NH), Version 1. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi:10.7265/N5GT5K3K.

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
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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
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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
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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
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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
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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
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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
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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

The summer melt season has come to a modest end. The summer of 2021 was relatively cool compared to the most recent years and September extent was the highest since 2014. It was nevertheless an eventful summer, with many twists and turns.

Overview of conditions

Figure 1a. Arctic sea ice extent for September 2021 was 4.92 million square kilometers (1.90 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
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Figure 1b. The map above compares the annual minimum set on September 16, 2021, with October 3, 2021. Light blue shading indicates the region where ice occurred on both dates, while white and medium blue areas show ice cover unique to September 16, 2021 and October 3, 2021, respectively. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for September averaged 4.92 million square kilometers (1.90 million square miles), the twelfth lowest in the 43-year satellite record. This is 1.35 million square kilometers (521,000 square miles) above the record low set in September 2012, and 1.49 million square kilometers (575,000 square miles) below the 1981 to 2010 average. The last 15 years (2007 to 2021) have had the 15 lowest September extents in the record.

The annual minimum extent occurred on September 16 and was the twelfth lowest minimum in the satellite record. Afterwards, ice extent increased primarily in the Beaufort Sea region, with the large irregular open water region that existed in mid-September filling in with ice (Figure 1b). The ice edge also expanded in the East Siberian Sea. The East Greenland Sea has been largely ice free for much of the summer, but sea ice is now expanding southward.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of October 5, 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 red. 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
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for September 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
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After the minimum set on September 16, extent began rising fairly rapidly as the scattered open water areas in the Beaufort and Chukchi Seas began to fill in (Figure 2a). Ocean temperatures remained low in this region because of the late ice retreat that limited the amount of solar insolation absorbed by the ocean. The cooler ocean allowed a quick freeze up as air temperatures dropped below freezing. Overall, extent increased 430,000 square kilometers (166,000 square miles) between the 16 and the end of the month, about the same as the increase for the 1981 to 2010 average.

During September, air temperatures at the 925 mb (about 2,500 feet above the surface) were higher than average over most of the Arctic Ocean (Figure 2b). Temperatures were up to 4 degrees Celsius (7 degrees Fahrenheit) above average in the East Greenland Sea, likely reflecting the unusual lack of ice in the region, allowing ocean heat to warm the lower atmosphere. The one notable cold region was in the East Siberian Sea; temperatures in the last two weeks of September were 3 to 4 degrees Celsius (5 to 7 degrees Fahrenheit) below average.

September 2021 compared to previous years

Figure 3. Monthly September ice extent for 1979 to 2021 shows a decline of 12.7 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in September sea ice extent over the satellite records is 81,200 square kilometers (31,400 square miles) per year, or 12.7 percent per decade relative to the 1981 to 2010 average (Figure 3). September marks the month of the largest linear trend in ice extent, both in absolute terms and percentage loss. Overall, since 1979, September has lost 3.49 million square kilometers (1.35 million square miles) of ice, based on the linear trend values. This is equivalent to about twice the size of Alaska.

There was little net change in extent over the month of September—extent declined during the first half of the month and then increased in the second half. This year, extent was 5.17 million square kilometers (2.00 million square miles) on September 1 and 5.15 million square kilometers (1.99 million square miles) on September 30.

Antarctica’s unusual sea ice maximum

Figure 4a. The graph above shows Antarctic sea ice extent as of October 3, 2021, along with daily ice extent data for three previous years including the record low year. 2021 is shown in blue, 2016 in green, 2014 in black, and 2017 in dashed red. 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
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Figure 4b. This map compares Antarctic sea ice extent for September 1, 2021, with October 3, 2021. Light blue shading indicates the region where ice occurred on both dates, while white and medium blue areas show ice cover unique to September 1, 2021 and October 3, 2021, respectively. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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As noted in our earlier posts, Antarctic sea ice extent has been above average for the past several months, culminating in late August when extent was the fifth highest in the satellite record (Figure 4a). However, since peaking on September 1, sea ice extent has declined steeply. At the beginning of October, Antarctic sea ice extent was nearly 600,000 square kilometers (232,000 square miles) lower than the beginning of the month (Figure 4a). The maximum observed on September 1 was 18.75 million square kilometers (7.24 million square miles) is very likely to be the annual maximum for the year, marking the second-earliest seasonal maximum in the 43-year satellite record. Sea ice loss since September 1 has been greatest in the Ross Sea, Bellingshausen Sea, and Weddell Sea sectors (Figure 4b).

For the interior of the Antarctic continent, specifically the region near the South Pole, the winter of 2021 was among the coldest on record. At the National Science Foundation’s Amundsen-Scott South Pole Station, temperatures for June, July, and August were 3.4 degrees Celsius (6.1 degrees Fahrenheit) lower than the 1981-to-2010 average at -62.9 degrees Celsius (-81.2 degrees Fahrenheit). This is the second coldest winter (June-July-August months) on record, behind only 2004 in the 60-year weather record at the South Pole Station. For the polar darkness period, from April through September, the average temperature was -60.9 degrees Celsius (-77.6 degrees Fahrenheit), a record for those months. The unusual cold was attributed to two extended periods of stronger-than-average encircling winds around the continent, which tend to isolate the ice sheet from warmer conditions. A strong upper-atmosphere polar vortex was observed as well, leading to a significant ozone hole. The ozone hole appears to have peaked as of this post, with initial measurements reporting that it is in the upper quartile (top 25 percent) of ozone reduction events since 1979.

2021 Arctic summer in review

Figure 5a. This graph shows daily sea ice extent in the Laptev Sea for May through September for 2021 (red) and the 1979 to 2020 minimum (dashed gray) as compared to the 1981 to 2010 average. At two periods in time the Laptev sea ice extent in 2021 fell to the lowest extent in the satellite record, as marked in red “record low.”

Credit: W. Meier, National Snow and Ice Data Center
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Figure 5b. This plot shows average sea level pressure in the Arctic in millibars for 2019, 2020, 2021, and the 1981 to 2010 average. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Figure 5c. This graph shows the months of June, July, and August (JJA) at 925 mb air temperature averaged over 70 to 90 degrees N latitude for 1979 to 2021.

Credit: National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis
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Figure 5d. These maps show sea surface temperatures (SST) in mid-September for (a) 2021, (b) 2020, (c) 2019, and (d) 2018. SST data from are from the National Ocean and Atmospheric Administration (NOAA). Circles indicate buoy data points with SST or sea ice concentration.

Credit: Upper layer Temperature of the Polar Oceans (UpTempO), University of Washington
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Figure 5e. The top maps show sea ice age at the week of the minimum for 1984, on the left, and 2021, on the right. The bottom time series graph shows the total extent of age categories for 1984 to 2021, within the Arctic Ocean Domain (inset).

Credit: Tschudi et al., 2019a and Tschudi et al., 2019b
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The spring and summer of 2021 were notable for the extremely early melt and retreat of ice in the Laptev Sea, resulting in record low June sea ice extent in that region and much lower extent compared to average throughout the summer (Figure 5a). By contrast, sea ice retreat within the Beaufort and Chukchi Seas was slow and the ice edge remained near its long-term average position throughout summer. At least in part, this reflects the unusually strong transport of thick, old ice into the region during winter; thicker ice is more resistant to melting out in summer. Another interesting feature was the lack of summer ice in the East Greenland Sea. Transport of ice through Fram Strait southward generally feeds a tongue of ice along the eastern coast of Greenland through summer. The lack of summer ice this year can be tied to wind patterns inhibiting this southward flow of ice. Thinner ice encountering warm Atlantic waters may have also played a role.

The summer of 2021 was dominated by low sea level pressure over the Arctic Ocean and a lack of a strong Beaufort Gyre circulation (Figure 5b). Cyclone activity over the central Arctic Ocean tends to peak in summer, with cyclones forming over the Eurasian continent migrating into the region and cyclogenesis (cyclone formation) over the Arctic Ocean itself. However, the pattern is quite variable. While the summer of 2021 was characterized by frequent cyclone activity, other summers, like 2019 and 2020, had few cyclones in that region where high pressure prevailed (Figure 5b). Cyclones found over the central Arctic Ocean are of a type known as “cold cored,” which helps to account for the summer of 2021 being fairly cool (Figure 5c).

The ocean surface also remained relatively cool during summer 2021. Sea surface temperatures (SSTs) at summer’s end were lower than the three previous years, based on buoys and the National Oceanic and Atmospheric Administration satellite data (Figure 5d). The summer of 2021 had widespread areas of near-freezing SSTs near the ice edge; this is indicative of late season ice melt cooling the surface and little incoming solar radiation. Low SSTs enable rapid freeze up, as is occurring in those regions. Also, the area with SSTs greater than 5 degrees Celsius (9 degrees Fahrenheit), is much smaller and widespread than in recent years.

Despite September total ice extent being high compared to recent years, the amount of multiyear ice as assessed from ice age (Figure 5e) reached a near-record low, with an extent of only 1.29 million square kilometers (498,000 square miles), just slightly above the value of 1.27 million square kilometers (490,000 square miles) at the end of the 2012 melt season.

IceBird: Summer sea ice thickness north of Greenland and Fram Strait

Figure 6. This graph shows average, in red, and modal, in blue, sea ice thickness from the IceBird campaigns between 2001 and 2021. The average thickness is the average of all estimates; the modal thickness is the most frequently observed thickness estimate.

Credit: Belter et al. 2021
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In August 2021, the IceBird Summer campaign continued its observations of sea ice thickness north of Greenland and within northern Fram Strait by means of airborne electromagnetic sounding. Our colleagues J. Belter, T. Krumpen, S. Hendricks, and C. Haas at the Alfred Wegener Institute provided a summary of the campaign. The observed average sea ice thickness of 1.7 meters (5.6 feet) was among the lowest observed since 2001 (Figure 6). Ice motion tracking reveals that the sea ice in this area was originally first-year ice that formed in the shallow shelf in the central Laptev Sea. It was then transported across the Arctic Ocean via the Transpolar Drift Stream. Near the campaign’s base at Station Nord, the reoccurrence of the Wandel Sea polynya led to enhanced melting once the winds had dispersed the ice north.

Nansen Legacy: The northern Barents Sea before and during the 2021 melt season

Figure 7a. This graph shows sea ice extent in the Barents Sea from the Multisensor Analyzed Sea Ice Extent – Northern Hemisphere (MASIE-NH) product, with the periods of the four cruises highlighted in color.

Credit: Norwegian Polar Institute
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Figure 7b. Sea smoke in leads in between sea ice northeast of Svalbard in March 2021, during a Nansen Legacy research expedition with RV Kronprins Haakon, illustrating the heat exchange between the cold atmosphere and relatively warmer ocean. 

Credit: Sebastian Gerland, Norwegian Polar Institute
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During March to September 2021 a series of interdisciplinary research expeditions to the northern Barents Sea were conducted as part of the Norwegian “Nansen Legacy” project. A dedicated sea ice research team worked alongside researchers focused on ocean and ecosystem dynamics, with the aim of understanding the northern Barents Sea ocean, ice, and ecosystem interactions over the period from the regional sea ice maximum to seasonally ice-free conditions (Figure 7a). Our colleagues D. Divine, S. Gerland, A. Steer, and S. Lind at the Norwegian Polar Institute in Tromsø, Norway, provided a summary of the expeditions.

Observations during the voyages revealed a highly dynamic sea ice cover in the area. In March, the northern Barents Sea was covered with mainly level 0.4-to-0.6-meters (1.3-to-2.0-feet) thick sea ice, locally formed sea ice with a tendency towards a greater fraction of ridged ice north of Svalbard. This type of ice persisted in the central Barents Sea through April and May. Long-lasting, stable cold conditions in February to mid-March promoted the formation of large ice floes—often more than 1 square kilometer (0.39 square miles). This relatively thin ice cover experienced a rapid transformation during a single storm event from March 22 to 24, 2021, breaking into floes ranging from 20 to 100 meters (66 to 328 feet) length. At the shelf-break north of the Barents Sea in March 2021, the team observed strong heat losses from the ocean surface, seen as sea smoke (Figure 7b). Measurements also revealed upward oceanic heat fluxes from the deeper Atlantic layer, situated below about 100 meters (328 feet) depth. This likely limited local sea ice production in this region. The relatively warm water in the upper 100 meter (328 feet) likely prevented the ice from further thickening in this region, despite continuous cold atmospheric conditions in the area with air temperatures below -20 degrees Celsius (-4 degrees Fahrenheit), favorable for ice growth.

From May through July, the area northeast of Svalbard was dominated by 1.0 to 1.5 meters (3.3 to 4.9 feet) thick first-year ice that originated in the central Arctic Ocean. In July, sea ice was present only in the very north end of the research area, near the boundary with the Nansen Basin. By August and September, this part of the Barents Sea was ice free.

Acknowledgements

Thanks to Matthew Lazzara of the Antarctic Meteorological Research and Data Center at the University of Wisconsin-Madison, and to Kyle Clem of Victoria University in Wellington, New Zealand.

Further reading

Belter, H. J., T. Krumpen, L. V. Albedyll, T. A. Alekseeva, G. Birnbaum, S. V. Frolov, S. Hendricks, A. Herber, I. Polyakov, I. Raphael, R. Ricker, S. S. Serovetnikov, M. Webster, and C. Haas. 2021. Interannual variability in Transpolar Drift summer sea ice thickness and potential impact of Atlantification. The Cryosphere, 15, 6, 2575-2591, doi:10.5194/tc-15-2575-2021.

Krumpen, T., H. J. Belter, A. Boetius, et al. 2019. Arctic warming interrupts the Transpolar Drift and affects long-range transport of sea ice and ice-rafted matter. Scientific Reports 9, 5459, doi:10.1038/s41598-019-41456-y.

Mallett, R. D. C., J. C. Stroeve, S. B. Cornish, et al. 2021. Record winter winds in 2020/21 drove exceptional Arctic sea ice transport. Communications Earth & Environment 2, 149, doi:10.1038/s43247-021-00221-8

Erratum

On October 13, NSIDC scientists clarified the wording regarding the coldest winter on record for Antarctica: For the interior of the Antarctic continent, specifically the region near the South Pole, the winter of 2021 was among the coldest on record.

On September 16, Arctic sea ice likely reached its annual minimum extent of 4.72 million square kilometers (1.82 million square miles). The 2021 minimum is the twelfth lowest in the nearly 43-year satellite record. The last 15 years are the lowest 15 sea ice extents in the satellite record. The amount of multi-year ice (ice that has survived at least one summer melt season), is one of the lowest levels in the ice age record, which began in 1984.

In the Antarctic, sea ice extent is now falling rapidly, but it is still too early to assume that the maximum has been reached. The maximum for Antarctic sea ice typically occurs in late September or early October. However, Antarctic sea ice extent is highly variable near the maximum because of storms acting to expand or compact the extended ice edge.

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October.

Overview of conditions

Figure 1. Arctic sea ice extent for September 16, 2021, was 4.72 million square kilometers (1.82 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
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On September 16, sea ice reached its annual minimum extent of 4.72 million square kilometers (1.82 million square miles) (Figure 1). In response to the setting sun and falling temperatures, ice extent has begun rising and will continue to rise through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.

The minimum extent was reached two days later than the 1981 to 2010 median minimum date of September 14. The interquartile range of minimum dates is September 11 to September 19.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent on September 16, 2021, along with several other recent years and the record minimum set in 2012. 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
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This year’s minimum set on September 16 was 1.33 million square kilometers (514,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012 (Figure 2). It is also 1.50 million square kilometers (579,000 square miles) below the 1981 to 2010 average minimum extent, which is equivalent to twice the size of Texas.

In the 43-year-satellite record, 15 of the lowest minimums have all occurred in the last 15 years.

Multiyear ice extent is one of the lowest on record. First-year-ice coverage increased dramatically since last year, jumping from 1.58 million square kilometers (610,000 square miles) to 2.71 million square kilometers (1.05 million square miles). The increase in total extent from last year’s minimum to this year’s is hence comprised of first-year ice.

The overall, downward trend in the minimum extent from 1979 to 2021 is 13.0 percent per decade relative to the 1981 to 2010 average. The loss of sea ice is about 80,600 square kilometers (31,100 square miles) per year, equivalent to losing the size of the state of South Carolina or the country of Austria annually.

Fifteen lowest minimum Arctic sea ice extents (satellite record, 1979 to present)

Values within 40,000 square kilometers (15,000 square miles) are considered tied. The 2020 value has changed from 3.74 to 3.82 million square kilometers (1.47 million square miles) when final analysis data updated near-real-time data. The 2020 date of minimum also changed from September 15 to September 16. 

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
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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
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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
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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
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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. 

Credit: Canadian Ice Service
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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
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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.

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 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
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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
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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
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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
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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
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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
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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
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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 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
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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
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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.” Arctic, 5(4), pp.211-223.

Koenig, L. S., K. R. Greenaway, M. Dunbar, and G. Hattersley-Smith. 1952. Arctic ice islands. Arctic, 5(2), pp.66-103.

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

Sea ice loss during the first half of August stalled, though ice in the Beaufort Sea is finally starting to weaken. The Northern Sea Route appears closed off in 2021, despite being open each summer since 2008.

Overview of conditions

Figure 1a. Arctic sea ice extent for August 17, 2021 was 5.77 million square kilometers (2.23 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
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Figure 1b. This satellite image of the Arctic Ocean on August 8, 2021, shows sea ice break up in the Northern Chukchi and Beaufort Seas. The magenta outline depicts smoke from Siberian fires moving over Arctic sea ice. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra and Aqua satellites took this image.

Credit: National Snow and Ice Data Center/NASA Worldview
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As of August 17, sea ice extent stood at 5.77 million square kilometers (2.23 million square miles), tracking above the last six years, as well as 2011, 2012, and 2007 (Figure 1a). Sea ice loss stalled between August 8 and 11 before picking up the pace again. While overall decline in total ice extent has slowed, the ice cover is becoming more diffuse within the northern Chukchi Sea and the western Beaufort Sea. Further reductions are likely in that region (Figure 1b). Ice motion during the first week of August pushed sea ice in the Beaufort Sea southwards, and ice within the Chukchi Sea moved towards the East Siberian Sea. While sea ice in the western Arctic has been more extensive than in recent summers, the Laptev Sea has lost more sea ice thus far than at any other time in the satellite record. However, ice remains south of Severnaya Zemlya in the Kara Sea, blocking the Northern Sea Route. Further south in the East Greenland Sea, there is only 119,000 square kilometers (45,900 square miles) of sea ice, the second least amount of ice for this time of year following 2002.

Conditions in context

Figure 2a. Arctic sea ice extent for August 17, 2021 was 5.77 million square kilometers (2.23 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
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, between August 1 to 15, 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
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An unusually strong high-pressure system dominated over Siberia during the first half of August, extending towards the pole. This high pressure was coupled by low pressure over the Greenland Ice Sheet, promoting strong southwards ice motion from the center of the Arctic Ocean towards the North American and Siberian coastlines. Overall, air temperatures at the 925 millibar level (about 2,500 feet above the surface) were about 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average over most of the Arctic Ocean, with air temperatures up to 7 degrees Celsius (13 degrees Fahrenheit) above average in the Kara Sea near Severnaya Zemlya (Figure 2b). However, while temperatures have mostly been higher than average, this is the time of the year when air temperatures start to drop as the sun dips lower on the horizon. Surface melting ends and melt ponds begin to refreeze, and thus remaining ice loss is primarily from below the sea ice, melting out the bottom from heat in the upper layer of the ocean.

Timing of melt onset is a mixed bag

Figure 3. This map shows the date of sea ice melt onset in the Arctic for the 2021 melt season compared to the 1981 to 2010 average. Shades in red depict sea ice melt up to 30 days earlier than average, while shades in blue depict melt up to 30 days later than average.

Credit: Walt Meier, NSIDC; data courtesy J. Miller, NASA Goddard
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This summer sea ice retreated early within the Laptev Sea. This was in part a result of earlier melt onset, starting more than a month earlier than the 1981 to 2010 average over parts of the Laptev Sea (Figure 3). Earlier melt onset allows for earlier loss of the winter snow cover and earlier development of melt ponds that reduce the surface reflectivity, known as albedo. A lower surface albedo enhances summer ice melt by absorbing more of the sun’s energy. Melt this summer was also unusually early within Hudson Bay and Davis Strait, on average 16 days earlier. The sea ice within the Barents Sea near Franz Josef Land and within the Kara Sea around Novaya Zemlya also started to melt more than a month earlier than average. On the other hand, melt was about two to three weeks later than average in the northern Beaufort Sea, despite earlier melt observed near the coast. This later melt onset may have helped to reduce ice loss in the region this summer. Overall, pan-Arctic melt onset was five days earlier than average.

Multiyear ice near record low

Figure 4a. This graph shows the near record-low amount of multiyear ice in the Arctic as of week 31 (July 30 to August 5) of the 2021 melt season, comparing this year to the same week in previous years of the satellite record that began in 1979. Historical data through 2020 are provided by Tschudi et al., 2019a and quicklook data for 2021 by Tschudi et al., 2019b

Credit: Robbie Mallett
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Figure 4b. This graph compares the area of multiyear ice in the Arctic between 2021, 2020, and the average from 2008 to 2019 as it melts out throughout the spring and summer. The grey lines depict previous years for general comparison. The area is calculated by adding all pixels in the Arctic that are older than one year based on the NSIDC ice age data product, and multiplying by the area per pixel of each grid cell. Historical data through 2020 are provided by Tschudi et al., 2019a and quicklook data for 2021 by Tschudi et al., 2019b

Credit: Robbie Mallett
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While the multiyear ice that advected into the Beaufort Sea has helped to stabilize ice loss in that region, multiyear ice for 2021 in the Arctic as a whole is at a record low. Based on ice age classification, the proportion of multiyear ice in the Arctic during the first week of August is at 1.6 million square kilometers (618,000 million square miles). The loss of the multiyear ice since the early 1980s started in earnest after the 2007 record low minimum sea ice cover that summer, and while there have been slight recoveries since then, it has not recovered to values seen in the 1980s, 1990s, or early 2000s. This loss of the oldest and thickest ice in the Arctic Ocean is one of the reasons why the summer sea ice extent has not recovered, even when weather conditions are favorable for ice retention.

2021 Arctic sea ice minimum forecasts

Figure 5. This figure shows Arctic sea ice extent projections for the 2021 minimum using data through August 1, 2021. The projections are based on the average loss rates for the 1981 to 2010 average in red, the 2007 to 2020 average in green, 2012 rates in dotted purple, and 2006 rates in dotted teal.

Credit: Walt Meier, National Snow and Ice Data Center
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In about three or four weeks, Arctic sea ice will reach its minimum extent for the 2021 melt season. A community effort, called the Sea Ice Prediction Network (SIPN), each years runs the Sea Ice Outlook. The Outlook is a forum for researchers and other interested people to provide a seasonal forecast of the September monthly average extent and the daily seasonal minimum. One submission by Arctic Sea Ice News & Analysis (ASINA) team member Walt Meier uses ice extent loss rates from previous years to project this year’s ice loss through the end of September (Figure 5). Projections of the minimum and September average extent are initially submitted using data through the beginning of May as starting points and updated Outlooks can be provided in following months as conditions evolve. Figure 5 shows the latest projection starting with observations on August 1, submitted to the August Outlook. The projections are based on the average loss rates for four different rates using data from previous years. The August Outlook report will be published later this month.

Further reading

Babb, D. G., J. C. Landy, D. G. Barber, and R. J. Galley. 2019. Winter sea ice export from the Beaufort Sea as a preconditioning mechanism for enhanced summer melt: A case study of 2016. Journal of Geophysical Research: Oceans, 124, 6575– 6600. doi:10.1029/2019JC015053.

Mallett, R. D. C., J. C. Stroeve, S. B. Cornish, et al. 2021. Record winter winds in 2020/21 drove exceptional Arctic sea ice transport. Communication Earth Environment 2, 149. doi:10.1038/s43247-021-00221-8.