Springtime for the Arctic

Arctic sea ice extent for May 2018 was the second lowest in the satellite record. Above average temperatures and high sea level pressure prevailed over most of the Arctic Ocean, while some surrounding continental regions were colder than usual.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 million square miles). This was the second lowest May extent in the 39-year satellite record, and is 310,000 square kilometers (120,000 square miles) above May 2016, the record low for the month. Compared to May 2016, the ice cover remained slightly more extensive in the Barents and Kara Seas, within Baffin Bay, Davis Strait, and the southern Beaufort Sea, but less extensive in the Chukchi and East Greenland Seas.

In Svalbard, the average temperature for May 2018 was 6 degrees Celsius (11 degrees Fahrenheit) above average. By the end of the month, the north and west coasts of Svalbard were largely ice-free and a tongue of open water east of the islands extended northeast to Franz Joseph Land. According to NSIDC data, open water stretched as far north as ~82 degrees N at the end of May.

In the Chukchi Sea, open water developed to the west of Point Barrow, Alaska throughout the month. This may be in part a result of the inflow of warm waters from the Pacific, where sea surface temperatures were higher than average. It may also be due to the general lack of sea ice in the region that allows the ocean to readily absorb the sun’s energy. Ice retreat was also substantial within the Sea of Okhotsk, and little ice remains in the region. Hudson Bay began to open up, with a significant area of open water in the northwest sector of the bay.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 in purple, and 2012 in dotted 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.

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2018, along with daily ice extent data for four previous years and 2012, the year with record low minimum extent. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 in purple, and 2012 in dotted 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 departure from average sea level pressure in the Arctic, in millibars, for May 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division

Figure 2b. This plot shows departure from average sea level pressure in the Arctic, in millibars, for May 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

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

Figure 2c. This plot shows air temperatures at the 925 mb level averaged over the Arctic Ocean region. This region covers only oceans areas in the Arctic, bounded by the Bering Strait on the Pacific side, and Fram Strait and roughly the 20 degree E meridian between Svalbard and Norway.||Credit: A. P. Barrett, NSIDC

Figure 2c. This plot shows air temperatures at the 925 mb level averaged over the Arctic Ocean region. This region covers only ocean areas in the Arctic, bounded by the Bering Strait on the Pacific side, and Fram Strait and roughly the 20 degree E meridian between Svalbard and Norway.

Credit: A. P. Barrett, NSIDC
High-resolution image

The atmospheric pattern (Figure 2b) for May was characterized by a region of above average sea level pressure centered over the Fenno-Scandinavian Peninsula and below average pressure centered over Greenland. This pattern helped to funnel warm winds from the south into the Barents Sea sector favoring retreat of ice. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) in the Barents Sea were up to 5 degrees Celsius (9 degrees Fahrenheit) above average (not shown). On the Pacific side, departures from average sea level pressure were small and a fairly typical Beaufort Sea High and Aleutian Low pattern reigned for much of the month. Overall it was warm across the Arctic Ocean with temperatures at the 925 hPa level ranging between 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average for the month. By contrast, conditions over land regions surrounding the Arctic were relatively cool. Parts of Central Siberia and Nunavut in northern Quebec saw temperatures more than 5 degrees Celsius (9 degrees Fahrenheit) below average. However, Europe, eastern Asia and western North America were warmer than usual.

Air temperatures at the 925 mb level (about 2,500 feet above sea level) over the Arctic Ocean have been above average through most this year (Figure 2c). Temperatures were extremely high compared to typical conditions from January through early March. After a brief cold period in March, temperatures returned to near average and increased at typical rates through most of May.

While it is still relatively early in the melt season, images from the Moderate Resolution Imaging Spectroradiometer (MODIS) show considerable fracturing of multiyear ice floes in the Beaufort Sea. The early development of open water around these large ice floes can help accelerate melt through absorption of solar energy. Some of these ice floes appear already partially covered by melt ponds.

May 2018 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2018 shows a decline of 2.6 percent per decade.

Figure 3. Monthly May ice extent for 1979 to 2018 shows a decline of 2.6 percent per decade.

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

The linear rate of decline for May sea ice extent is 36,000 square kilometers (14,000 square miles) per year, or 2.6 percent per decade relative to the 1981 to 2010 average. Ice loss during the month was 1.7 million square kilometers (656,000 square miles), which was faster than the 1981 to 2010 average loss of 1.5 million square kilometers (579,000 square miles) for the month.

Another season for the Sea Ice Outlook

The Sea Ice Prediction Network is once again soliciting contributions to the Sea Ice Outlook predicting the September 2018 sea ice extent. This effort is coordinated by the Arctic Research Consortium of the United States (ARCUS). This is the second phase of the Sea Ice Prediction Network, and is currently funded by the National Science Foundation, the Office of Naval Research, and the United Kingdom’s National Environment Research Council. While all prediction methods are welcome, a new focus of the project is to assess the economic value of seasonal ice forecasts. To make the forecasts more useful to stakeholders, there is an increased emphasis on predicting the spatial pattern of the ice cover for September, not just the total extent. The Sea Ice Outlook will summarize contributions and assess the seasonal evolution of conditions each month through summer and in post-season reports at https://www.arcus.org/sipn.

Autumn in Antarctica

Figure 4a. Arctic sea ice extent for June 1, 2018 was 11.0 million square kilometers (4.2 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 4a. Arctic sea ice extent for June 1, 2018 was 11.0 million square kilometers (4.2 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

Sea ice extent in the Southern Ocean grew steadily in May at the rate of 123,000 square kilometers (47,000 square miles) per day, somewhat faster than the 1981 to 2010 average growth rate of 108,000 square kilometers (42,000 square miles) per day. This pushed Antarctic ice extent from third lowest at the start of the month to sixth lowest by June 1. Ice extent was near average for all regions except for a broad section of the far eastern Weddell Sea, where ice extent was less than the 1981 to 2010 average. The eastern Ross, Amundsen, and Bellingshausen Seas began the month with less ice cover than average, but rapid growth in these regions brought ice extent to near average by the end of the month.

Reference

Nilsen, T. “Warmest May ever on Arctic Islands,” The Barents Observer, June 3, 2018, 11:00 a.m., MST, https://thebarentsobserver.com/en/ecology/2018/06/warmest-may-ever-arctic-islands.

2018 winter Arctic sea ice: Bering down

The 2018 winter sea ice maximum has passed, and the melt season has begun. The most notable aspect of the 2017 to 2018 winter ice extent was the persistently low ice extent in the Bering Sea. While December, January, and February were characterized by very warm conditions over the Arctic, March temperatures were mixed, with cool conditions over the Eurasian side and moderately warm conditions over the North American side.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2018 was 14.3 million square kilometers (5.52 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for March 2018 was 14.30 million square kilometers (5.52 million square miles). The magenta line shows the 1981 to 2010 average extent for the month. Sea Ice Index data. About the data

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

Arctic sea ice extent for March 2018 averaged 14.30 million square kilometers (5.52 million square miles), the second lowest in the 1979 to 2018 satellite record. This was 1.13 million square kilometers (436,300 square miles) below the 1981 to 2010 average and 30,000 square kilometers (11,600 square miles) above the record low March extent in 2017. Extent at the end of the month was far below average in the Bering Sea, as it has been for the past several months, and slightly below average in the far northern Atlantic Ocean and Barents Sea. Ice extent was slightly above average in the Sea of Okhotsk.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of April 4, 2018, along with daily ice extent data for four previous years, and the record low year. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2011 to 2012 in dotted 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.

Figure 2a. The graph above shows Arctic sea ice extent as of April 4, 2018, along with daily ice extent data for four previous years, and the record low year. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2011 to 2012 in dotted 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 temperatures at the 925 hPa level in degrees Celsius in the Arctic for March 2018. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for March 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

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

Figure 2c. This plot shows the average sea level pressures in the Arctic (in millibars) at the 925 hPa level for March 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

Figure 2c. This plot shows the average sea level pressure in the Arctic at the 925 hPa level, in millibars, for March 2018. Yellows and reds indicate higher than average air pressure; blues and purples indicate lower than average air pressure.

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

Overall, ice extent for March 2018 changed little. Extent reached the annual maximum on March 17 and declined by March 31 to nearly the same level as at the beginning of the month. Ice loss following the seasonal maximum has been almost entirely restricted to the Bering Sea and the Sea of Okhotsk, with slight increases in extent in the Barents Sea and near Svalbard.

Air temperatures at the 925 hPa level (about 2,500 feet above sea level) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) higher than average in regions near Greenland and Alaska. Cooler conditions prevailed over Scandinavia, the Kara Sea, and far eastern Siberia, where temperatures were generally 4 to 7 degrees Celsius (7 to 13 degrees Fahrenheit) below average.

Higher than average sea level pressure was present over the western Arctic, including Canada, the Beaufort Sea, and Greenland, while lower than average sea level pressure prevailed over most of Europe and Siberia. This pattern was associated with winds from the south in the Bering Sea and Alaska, helping to push ice toward the pole. Conversely, over Scandinavia and the Barents Sea this pressure pattern resulted in winds from the northeast that pushed Arctic air onto the northern Eurasian landmass leading to colder air temperatures.

The Arctic Oscillation (AO), an indicator for general wind, precipitation, and temperature patterns in the Arctic, was strongly negative in early March, reflecting the higher than average sea level pressure in the western Arctic. This negative phase is characterized by a weakening of the circumpolar wind pattern, a pattern that favors cold air outbreaks over much of the United States as well as parts of Europe and Asia.

March 2018 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 201X shows a decline of 2.7 percent per decade.||Credit: National Snow and Ice Data Center

Figure 3. Monthly March ice extent for 1979 to 2018 shows a decline of 2.7 percent per decade.

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

The linear rate of decline for March ice extent is 42,200 square kilometers (16,400 square miles) per year, or 2.7 percent per decade relative to the 1981 to 2010 average.

Review of winter season 2017 to 2018

Figure 4. This plot shows the departure from average air temperatures in the Arctic at the 925 hPa level, in degrees Celsius, for December 2017 and January and February in 2018. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division| High-resolution image

Figure 4. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for December 2017 and January and February in 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

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

Unusually warm conditions and some prominent warm air intrusions characterized the 2017 to 2018 winter over the Arctic Ocean. Mean air temperature for the months of December, January, and February combined (the climatological winter season) was as much as 7 degrees Celsius (13 degrees Fahrenheit) higher than average, and nearly the entire Arctic Ocean was 4 degrees Celsius (7 degrees Fahrenheit) higher than average. This is the fourth year in a row that unusual jet stream patterns have led to warm air intrusions over the Arctic Ocean. However, some Arctic and subarctic land areas experienced unusually cold periods during the winter. Recent studies show that the frequency and intensity of warm air intrusions has increased in the last few years, particularly in the Atlantic sector, helping to reduce ice growth in the Barents Sea. The winter of 2017 to 2018 marks the second year in a row of pronounced warming events in the Pacific sector.

Deep snow in Russia and Europe

Figure 5. These images show the Northern Hemisphere water equivalent of snow cover in millimeters (top) and the Northern Hemisphere Total snow mass from October 2017 to March 31, 2018, in gigatons.

Figure 5. These images show Northern Hemisphere water equivalent of snow cover in millimeters (top) and Northern Hemisphere total snow mass in gigatons (bottom) from October 2017 to March 31, 2018.

Credit: GlobSnow Project and the Finnish Meteorological Institute
High-resolution image

Snow cover extent on the land masses surrounding the Arctic Ocean was average this past winter. However, an analysis of the snow cover thickness and density showed that the total snow mass this past winter was high. Estimates of total snow mass as of March 31 showed that the Northern Hemisphere had nearly 700 billion tons more snow this winter than the 1982 to 2012 average. Many areas of Russia and northern Europe had more than 150 millimeters (6 inches) of water-equivalent on the ground, present as deep snow cover. Snow extent had been above average the entire autumn-winter season but grew to exceptional levels beginning in February. Although the total snow mass has begun to decrease, it is still far above average. The analysis is based on many sources of snow and snow depth data, including passive microwave data produced by NSIDC (EASE-Grid Snow Water Equivalent and Daily Snow Cover), and data derived from several other groups from the European Space Agency and the National Oceanographic and Atmospheric Administration.

Sea ice drift in the Arctic Ocean

Figure 6. This plot shows monthly average sea ice motion in the Arctic for the months of January, February, and March in 2018. Credit: NSIDC courtesy Ocean and Sea Ice Satellite Application Facility (OSI-SAF)

Figure 6. This plot shows monthly average sea ice motion in the Arctic, in centimeters per second, for the months of January, February, and March in 2018.

Credit: Alek Petty/NASA Goddard Space Flight Center (GSFC) and the Ocean and Sea Ice Satellite Application Facility (OSI-SAF)
High-resolution image

Plots of monthly average sea ice motion for January, February, and March 2018 reveal pronounced changes in drift direction, since sea ice movement is largely controlled by winds, and therefore storms and pressure patterns. The maps include averages of sea surface temperature outside of the ice-covered area, and indicate that the surface of both the northern Pacific and northern Atlantic were substantially warmer relative to a 1982 to 2015 reference period. Strong Beaufort Gyre and Transpolar Drift patterns were present for January and March of 2018. Ice motion and sea surface temperature data are based on a multi-sensor estimate created by the Ocean and Sea Ice Satellite Application Facility (OSI-SAF), a European meteorological consortium.

Seasonal increase in Antarctic sea ice

After reaching a minimum extent for the year on February 20 and 21, Antarctic sea ice grew rapidly in March 2018. Sea ice extent averaged 3.53 million square kilometers (1.36 million square miles) for the month, not far below the 1981 to 2010 average of 4.03 million square kilometers (1.56 million square miles). Growth was especially rapid in the Amundsen and Ross Seas, nearly erasing the area of below-average sea ice extent that had been in the eastern Ross Sea and western Amundsen in early March.

Rapid sea ice growth in the Amundsen and eastern Ross Seas was reflected in temperatures at the 925 hPa level that were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average across the Pine Island Bay region. This is likely related to cool winds from the south coming up against the west side of a low-pressure area over the Bellingshausen Sea. By comparison, temperatures 2.5 to 4.5 degrees Celsius (4 to 8 degrees Fahrenheit) higher than average were the rule over much of the continental interior from Dronning Maud Land to northern Victoria Land along the Transantarctic Mountains. The index of the strength of the circumpolar vortex (or Southern Annular Mode) was near-neutral for March.

References

Boisvert, L. N., A. A. Petty, and J. Stroeve. 2016. The Impact of the Extreme Winter 2015/16 Arctic Cyclone on the Barents–Kara Seas, Bulletin of the American Meteorological Society, doi:10.1175/MWR-D-16-0234.1.

Graham, R. M., L. Cohen, A. A. Petty, L. N. Boisvert, A. Rinke, S. R. Hudson, M. Nicolaus, and M. A. Granskog. 2017. Increasing frequency and duration of Arctic winter warming events, Geophysical Research Letters, 44, 6974–6983, doi:10.1002/2017GL073395.

Ricker, R., S. Hendricks, F. Girard-Ardhuin, L. Kaleschke, C. Lique, X. Tian-Kunze, M. Nicolaus, and T. Krumpen. 2017. Satellite observed drop of Arctic sea ice growth in winter 2015-2015, Geophysical Research Letters, doi:10.1002/2016GL072244.

Rinke, A., M. Maturilli, R. M. Graham, H. Matthes, D. Handorf, L. Cohen, S. R. Hudson, and J. C. Moore. 2017. Extreme cyclone events in the Arctic: Wintertime variability and trends , Environmental Research Letters, 12 (9), 094006, doi:10.1088/1748-9326/aa7def.

Correction

On April 20, we revised a sentence under the section Seasonal increase in Antarctic sea ice. The sentence originally read “Growth was especially rapid in the Amundsen and eastern Ross Sea, where sea ice was nearly absent at the time of the minimum extent, and along the East Antarctic coast, where many areas now exceed the daily median extent for the end of March.” We revised it to “Growth was especially rapid in the Amundsen and Ross Seas, nearly erasing the area of below-average sea ice extent that had been in the eastern Ross Sea and western Amundsen in early March.”

 

Arctic sea ice maximum at second lowest in the satellite record

Arctic sea ice appears to have reached its annual maximum extent on March 17. This is the second lowest Arctic maximum in the 39-year satellite record. The four lowest maximum extents in the satellite record have all occurred in the past four years. NSIDC will post a detailed analysis of the 2017 to 2018 winter sea ice conditions in our regular monthly post in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 17, 2018 was 14.48 million square kilometers (5.59 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for March 17, 2018 was 14.48 million square kilometers (5.59 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On March 17, 2018, Arctic sea ice likely reached its maximum extent for the year, at 14.48 million square kilometers (5.59 million square miles), the second lowest in the 39-year satellite record, falling just behind 2017. This year’s maximum extent is 1.16 million square kilometers (448,000 square miles) below the 1981 to 2010 average maximum of 15.64 million square kilometers (6.04 million square miles).

The four lowest seasonal maxima have all occurred during the last four years. The 2018 maximum is 60,000 square kilometers (23,200 square miles) above the record low maximum that occurred on March 7, 2017; 40,000 square kilometers (15,400 square miles) below the 2015 and 2016 maxima (now tied for third lowest); and is 190,000 square kilometers (73,400 square miles) below the 2011 maximum, which is now fifth lowest.

In March 2017, we reported a new record maximum being set, with 2016 sliding to the second lowest, and 2015 the third lowest. In November 2017, we updated our calculation of the monthly average sea ice extent in the NSIDC Sea Ice Index, resulting in 2016 tying with 2015.

The date of the maximum this year, March 17, was five days later than normal compared to the 1981 to 2010 median date of March 12.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 22, 2018, along with daily ice extent data for five previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2012 in magenta, and 2011 to 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.

Figure 2. The graph above shows Arctic sea ice extent as of March 22, 2018, along with daily ice extent data for four previous years and the record low year. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in magenta, and the record low year 2011 to 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

The ice growth season ended with very low sea ice extents in the Bering Sea in the Pacific side of the Arctic, and in the Barents Sea in the Atlantic side of the Arctic. The regions of reduced ice cover reflect the combined influences of late autumn freeze-up as well as persistent high air temperatures throughout the winter. Freeze-up was especially late in the Chukchi Sea, due in part to the effects of strong ocean heat transport into the area through the Bering Strait. February then saw an early retreat of sea ice in the Bering Sea. Sea ice extent on the Atlantic side remained below average throughout the winter, which also appears linked to warm ocean waters. While air temperatures at the 925 hPa level (about 2,500 feet above sea level) remained well above average through most of winter, February saw an extreme heat wave over the Arctic Ocean. This is the fourth winter in a row that such heat waves have been recorded over the Arctic Ocean.

A late spurt in sea ice growth just prior to the maximum occurred in the Barents Sea near Novaya Zemlya; sea ice retreat just after the maximum was led by ice loss in the Bering Sea.

Table 1. Ten lowest maximum Arctic sea ice extents (satellite record, 1979 to present)

Rank Year In millions of square kilometers In millions of square miles Date
1 2017 14.42 5.57 March 7
2 2018 14.48 5.59 March 17
3 2015 14.52 5.61 February 25
3 2016 14.52 5.61 March 24
5 2011 14.67 5.66 March 9
5 2006 14.68 5.67 March 12
7 2007 14.77 5.7 March 12
8 2005 14.95 5.77 March 12
8 2014 14.96 5.78 March 21
10 2009 15.17 5.84 March 5

The Antarctic minimum

As noted in our previous post, in the Southern Hemisphere, sea ice reached its minimum extent for the year on February 20 and 21, at 2.18 million square kilometers (842,000 square miles). This year’s minimum extent was the second lowest in the satellite record, 70,000 square kilometers (27,00 square miles) above the record low set on March 3, 2017. The Antarctic minimum extent is 670,000 square kilometers (259,000 square miles) below the 1981 to 2010 average minimum of 2.85 million square kilometers (1.10 million square miles).

The February 20 and 21 timing of the minimum (the same extent was recorded on both dates) was just slightly earlier than the 1981 to 2010 median date of February 24 for the minimum. Over the satellite record, the Antarctic minimum has occurred as early as February 15 and as late as March 6.

Compared to the Arctic, air temperatures over the sea ice regions of Antarctica over the past season (austral summer) have been closer to their climatological average, hovering within 2 degrees Celsius (4 degrees Fahrenheit) of the 1981 to 2010 average. Relatively rapid and early growth of ice along the eastern Weddell Sea ice edge led the beginning of the autumn sea ice expansion.

Final analysis pending

Please note this is a preliminary announcement. At the beginning of April, NSIDC scientists will release a full analysis of winter conditions in the Arctic, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum.

A warm approach to the equinox

As temperatures at the North Pole approached the melting point at the end of February, Arctic sea ice extent tracked at record low levels for this time of year. Extent was low on both the Atlantic and Pacific sides of the Arctic, with open water areas expanding rapidly in the Bering Sea during the latter half of the month. On the other side of the globe, Antarctic sea ice has reached its minimum extent for the year, the second lowest in the satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2018 was 13.95 million square kilometers (5.39 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for February 2018 was 13.95 million square kilometers (5.39 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

Winter continues to be mild over the Arctic Ocean. Sea ice extent remained at record low daily levels for the month. Arctic sea ice extent for February 2018 averaged 13.95 million square kilometers (5.39 million square miles). This is the lowest monthly average  recorded for February, 1.35 million square kilometers (521,000 square miles) below the 1981 to 2010 average and 160,000 square kilometers (62,000) below the previous record low monthly average in 2017.

Extent was especially low in the Bering Sea where sea ice declined during the first three weeks of the month. The eastern part of the Bering Sea was largely ice-free for most of the month; extent was low on the western side, with the ice edge further north than normal. In the Chukchi Sea, extent also retreated during part of February, with open water developing north of the Bering Strait on both the Siberian and Alaskan coasts. As seen all winter, ice extent continued to be below average in the Barents Sea, and at the end of February, a wedge of open water formed north of Svalbard that extended well into the Arctic Ocean.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 4, 2018, along with daily ice extent data for four previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2011 to 2012 in dotted 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 average sea level pressures at the 925 hPa level for February 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

Figure 2b. This plot shows the average sea level pressures at the 925 hPa level for February 2018. 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 Division
High-resolution image

Figure 2c. This figure shows differences from the average in temperature in degrees Celsius and in addition to wind conditions for the period February 22 to 26, 2018. In addition, the North Atlantic Oscillation (NAO) index is shown in the lower left. This is a measure of the strength of the westerly winds in the North Atlantic. When the index is negative, the flow is wavier, which increases the probability of transport of warm air to Greenland from the south.

Figure 2c. This figure shows differences from average temperature in degrees Celsius, and wind conditions for the period February 22 to 26, 2018. In addition, the North Atlantic Oscillation (NAO) index is shown in the lower left. This is a measure of the strength of the westerly winds in the North Atlantic. When the index is negative, the flow is wavier, which increases the probability of transport of warm air to Greenland from the south.

Credit: European Centre for Medium-Range Weather Forecasts (ECMWF) IFS forecast model
High-resolution image

Low pressure centered just east of the Kamchatka Peninsula and high pressure centered over Alaska and the Yukon during February set up southerly winds that brought warm air and warm ocean waters into the Pacific side of the Arctic Ocean, impeding southward ice growth. This helps to explain the rapid loss of ice extent in the Bering Sea and the ice-free regions within the Chukchi Sea during the month. The warm air intrusion is evident in the 925 mb air temperatures, with monthly temperatures 10 to 12 degrees Celsius (18 to 22 degrees Fahrenheit) above average in the Chukchi and Bering Sea.

On the Atlantic side, low pressure off the southeast coast of Greenland and high pressure over northern Eurasia helped to funnel warm winds into the region and may have also enhanced the northward transport of oceanic heat. At the end of the month, this atmospheric circulation pattern was particularly strong, associated with a remarkable inflow of warm air from the south, raising the temperatures near the North Pole to above freezing, around 20 to 30 degrees Celsius (36 to 54 degrees Fahrenheit) above average. Air temperatures at Cape Morris Jesup in northern Greenland (83°37’N, 33°22’W) exceeded 0 degrees Celsius for several hours and open water formed to the north of Greenland at the end of the month. This is the third winter in a row in which extreme heat waves have been recorded over the Arctic Ocean. A study published last year by Robert Graham from the Norwegian Polar Institute showed that recent warm winters represent a trend towards increased duration and intensity of winter warming events within the central Arctic. While the Arctic has been relatively warm for this time of year, northern Europe was hit by extreme cold conditions at the end of February.

February 2018 compared to previous years

Figure 3. Monthly 2018 ice extent for 1979 to 2018 shows a decline of 3.1 percent per decade.

Figure 3. Monthly 2018 ice extent for 1979 to 2018 shows a decline of 3.1 percent per decade.

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

The linear rate of decline for February is 47,000 square kilometers per year (18,000 square miles per year), or 3.1 percent per decade.

Late freeze-up

freeze average and anomaly plots

Figure 4. These graphs show the average Arctic Ocean ice freeze-up dates for 1979 to 2017 (top) and the number of days that freeze-up occurred earlier (cool colors) or later (warm colors) than average (bottom).

Credit: J. Miller, NASA Goddard Space Flight Center
High-resolution image

This year, the freeze-up started earlier than average over much of the central Arctic Ocean, near average within Hudson and Baffin Bays, but significantly later than average elsewhere. Freeze-up was delayed by more than a month later than average within the Chukchi and Bering Seas on the Pacific side, and within the Barents and East Greenland Seas on the Atlantic side. In these regions freeze-up happened after December. Later freeze-up impacts sea ice thickness, reducing the number of days over which sea ice can grow during winter.

Winter navigation in the Arctic without an icebreaker

Figure 4. This figure shows the distribution of Arctic sea ice according to stage of development, , as of February 22, 2018. Pink shows new ice; purple shows young ice; blue shows first year thin ice; orange shows first year medium ice, red shows first year thick ice, brown shows old ice, and while shows glacial ice.

Figure 5. This figure shows the distribution of Arctic sea ice according to stage of development, , as of February 22, 2018. Pink shows new ice; purple shows young ice; blue shows first year thin ice; orange shows first year medium ice, red shows first year thick ice, brown shows old ice, and while shows glacial ice.

Credit: U.S. National Ice Center
High-resolution image

The Arctic Ocean is becoming more accessible for shipping. Most of the increase in commercial shipping traffic has been during summer, primarily through the Northern Sea Route along the coast of Siberia. However, this February a commercial tanker, the Eduard Toll, made the first crossing of the Northern Sea Route in winter. Improvements in ship-building and the development of ice-strengthened hull technology is a major factor in enabling winter access. Previous ice-strengthened ships could only navigate safely through 0.5 meter thick ice, compared to the 1.8 meter thick ice that the Eduard Toll cruised through. A fleet of six ships with similar technology is being constructed by a South Korean shipbuilder.

While the Northern Sea Route has tended to be dominated by first-year ice, which typically reaches a maximum of around 2 meters, thicker (3- to 4-meter) multi-year ice would be a hazard even to the newer, stronger ships. According to analysis by the U.S. National Ice Center, this year’s old ice (multi-year ice) has pulled completely away from the coast and the Northern Sea Route is dominated by first-year medium (0.7- to 1.2-meter) or first-year thick (1.2- to 2-meter) ice.

Opposite pole, same near-record low extent

Figure 6. The graph above shows Antarctic sea ice extent as of March 1, 2018, along with daily ice extent data for four previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2011 to 2012 in dotted magenta. 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.

Figure 6a. The graph above shows Antarctic sea ice extent as of March 1, 2018, along with daily ice extent data for four previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2016 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2011 to 2012 in dotted magenta. 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 6b. This figure shows Antarctic sea ice extent for February 28, 2018. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 6b. This figure shows Antarctic sea ice extent for February 28, 2018. Sea Ice Index data. About the data

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

In the Antarctic, sea ice extent reached its daily seasonal minimum, 2.18 million square kilometers (842,000 square miles), on February 20 and 21. This is the second lowest minimum extent in the satellite record, 70,000 square kilometers (27,000 square miles) above the record low, which was set on March 3, 2017. The February average was 2.29 million square kilometers (884,000 square miles), second lowest in the satellite record, and 20,000 square kilometers (7,700 square miles) above the record low February in 2017.

Sea ice in the Antarctic is highly variable from year to year—much more so than in the Arctic. This is clearly seen in the February extent values, where low 2011 values were followed by record or near-record highs in 2013, 2014, and 2015. This was then followed by record or near-record lows in 2017 and this year.

Sea ice extent is particularly low in the Ross and western Amundsen Sea region, and along the southern reaches of the Bellingshausen Sea. Patchy sea ice areas along the East Antarctic coast are near-average in extent.

Further reading

Graham, R. M., L. Cohen, A. A. Petty, L. N. Boisvert, A. Rinke, S.R. Hudson, M. Nicolaus, and M. A. Granskog. 2017. Increasing frequency and duration of Arctic winter warming events, Geophys. Res. Lett., 16, 6974-6983, doi:10.1002/2017GL073395.

Kretschmer, M., D. Coumou, L. Agel, M. Barlow, E. Tziperman, and J. Cohen. 2017. More persistent weak stratospheric polar vortex states linked to cold extremes, Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-16-0259.1.

 

 

Baked Alaska and 2017 in review

Arctic sea ice extent in December 2017 was below average in both the far northern Atlantic and the Bering Sea, and notably high temperatures prevailed over most of the Arctic, especially over Central Alaska. We look back at the year’s events, and examine Arctic sea ice trends since 1850 based on a new compilation of data from maps, ship reports, and other records.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2016 was 11.75 million square kilometers (4.54 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for December 2017 was 11.75 million square kilometers (4.54 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for December 2017 averaged 11.75 million square kilometers (4.54 million square miles), the second lowest in the 1979 to 2017 satellite record. This was 1.09 million square kilometers (420,900 square miles) below the 1981 to 2010 average and 280,000 square kilometers (108,100 square miles) above the record low December extent recorded in 2016. Extent at the end of the month was below average in the far northern Atlantic Ocean and Barents Sea, slightly above average in western Hudson Bay, and continued to be below average in the Bering and Chukchi Seas. Near-average conditions prevailed along the eastern coast of Greenland and in the Sea of Okhotsk.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 2, 2018, along with daily ice extent data for four previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2014 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2012 to 2012 in dotted 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.

Figure 2a. The graph above shows Arctic sea ice extent as of January 2, 2018, along with daily ice extent data for five previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2014 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2012 to 2012 in dotted 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 temperatures at the 925 hPa level in degrees Celsius for December 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division

Figure 2b. This plot shows the departure from average air temperatures at the 925 hPa level in degrees Celsius for December 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2c. This plot shows the departure from average sea level pressures at the 925 hPa level in degrees Celsius for December 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.|

Figure 2c. This plot shows the departure from average sea level pressures at the 925 hPa level in degrees Celsius for December 2018. 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 Division
High-resolution image

Ice growth during December 2017 averaged 59,800 square kilometers (23,100 square miles) per day. This was fairly close to the average rate for the month of 64,100 square kilometers (24,800 square miles) per day. Ice growth in the Chukchi Sea (very late compared to previous years), the Kara Sea, and the eastern Hudson Bay areas were the main regions of change in December. In contrast, the ice edge slightly retreated in the Barents Sea near Franz Josef Land.

December air temperatures at the 925 hPa level (about 2,500 feet above sea level) throughout the Arctic Ocean were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above average. Prominent warm spots were found over north Central Asia and Central Alaska (more than 10 degrees Celsius, or 18 degrees Fahrenheit above average), as well as over Svalbard and Central Siberia (nearly 6 degrees Celsius or 11 degrees Fahrenheit above average). Temperatures were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) below average in Eastern Siberia.

The air temperature pattern in December was similar to that seen in November, driven in part by the arrangement of high and low air pressure regions surrounding the Arctic. Below-average pressure over easternmost Siberia and above-average pressure over the Gulf of Alaska drove southwesterly winds into Central Alaska and the Yukon region. Warmth in the Central Arctic and in Svalbard was consistent with southerly winds arising from low pressure over Scandinavia and higher pressure in the Laptev Sea and Central Siberia.

The Arctic Oscillation (AO) is a key climate indicator for general wind, precipitation, and temperature patterns in the Arctic. The AO index was moderately positive through most of 2017, indicating a tendency toward strong circumpolar winds at high latitude and warm conditions in the mid-latitudes. December 2017 had a mix of conditions, resulting in a near-neutral AO state (as measured by the index).

December 2017 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

Figure 3. Monthly December ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

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

The linear rate of sea ice decline for December is 47,400 square kilometers (18,300 square miles) per year or 3.7 percent per decade. Recall from our previous post that NSIDC has revised the way in which monthly average extents are computed, which has some impacts on computed trends.

2017 year in review

Figure 4. These figures show trends for sea ice-over dates in the Beaufort (top) and Chukchi (bottom) Seas.

Figure 4. These figures show trends for ice-over dates in the Beaufort (top) and Chukchi (bottom) Seas. Sea Ice Index data.

Credit: R. Thoman, NOAA
High-resolution image

The winter of 2016 to 2017 saw record low winter sea ice extent and higher than average temperatures. Indeed, the first four months of 2017 set or tied record low extents for the month. However, the melt season progressed somewhat slowly from May through July, as storminess and relatively cool conditions began to prevail. As such, sea ice extent at the seasonal minimum, on September 13, ended up as eighth lowest.

Assessments of sea ice thickness modeled by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS), as well as sea ice age near the seasonal minimum extent indicate that Arctic sea ice remains very low in overall volume. As the year ended, ice extent remained especially low in the Chukchi and Bering Seas. As discussed in an earlier post, the unusually early seasonal ice retreat in the Chukchi Sea this past summer likely relates to a strong inflow of oceanic heat into the region via the Bering Strait. With more heat in the upper ocean at summer’s end, it takes longer for sea ice to form in autumn and winter. Colleague Rick Thoman of the National Oceanic and Atmospheric Administration (NOAA) National Weather Service has assembled a time series of the ice-over dates in both the Chukchi and Beaufort Seas based on the satellite passive microwave record (Figure 4). The ice-over date is defined as the first day that the ice concentration exceeds 95 percent in the region. The trends towards later freeze up in both seas is striking. This has an impact on sea ice thickness as the growth season is shortened, which may lead to thinner ice by the end of winter. On the other hand, later freeze up also means less time for snow accumulation on the sea ice. Since sea ice grows faster for a thinner snowpack, this may partially offset the impacts of late ice formation.

A longer record of Arctic sea ice extent

Figure 5a. This figure shows departures from 1850 to 2013 calendar-month averages of Arctic sea ice extent as a function of year (x-axis) and calendar month (y-axis). The color bar at the right shows magnitudes of departures from the average.

Figure 5a. This figure shows departures from 1850 to 2013 calendar-month averages of Arctic sea ice extent as a function of year (x-axis) and calendar month (y-axis). The color bar at the right shows magnitudes of departures from the average.

Credit: J. E. Walsh, F. Fetterer, J. S. Stewart, W. L. Chapman. 2016. Geographical Review; after a figure by J. Stroeve, National Snow and Ice Data Center
High-resolution image

Figure 5b. These sea ice concentration maps compare the lowest September minimum Arctic sea ice extents for the periods 1850 to 1900, 1901 to 1950, 1951 to 2000, and 2000 to 2013.||Credit: F. Fetterer/National Snow and Ice Data Center, NOAA

Figure 5b. These sea ice concentration maps compare the lowest September minimum Arctic sea ice extents for the periods 1850 to 1900, 1901 to 1950, 1951 to 2000, and 2000 to 2013.

Credit: F. Fetterer/National Snow and Ice Data Center, NOAA
High-resolution image

Using a compilation of maps, ship reports, and other records, NOAA has published monthly estimates of Arctic sea ice extent spanning 1850 to 2013. While data in the earlier part of the record is limited, the carefully constructed time series helps to put the more recent satellite record in a longer-term context. Figure 5a shows the decline in extent over the period of satellite observations standing out prominently in comparison with the rest of the record, especially in late summer and early autumn. An earlier period of unusually low summer sea ice extent around 1937 to 1943 (as compared to the 1850 to 2013 average) did not extend to the winter season, and was followed by a few years of significantly higher-than-average summer ice extents. Early in the record (1850 to 1900), winter ice extent was not particularly elevated relative to the 1850 to 2013 average, but summer sea ice extent was quite a bit higher higher than the average. As another way to place recent conditions into a longer context using this data set, we show the years of the lowest September extent recorded within the 50-year periods 1850 to 1900, 1901 to 1950, 1951 to 2000, along with the lowest over the period 2000 to 2013 (Figure 5b). The decline in extent is apparent.

Low sea ice extent in the Antarctic

Figure 6. Antarctic sea ice extent for December 2017 was 9.34 million square kilometers (3.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 6. Antarctic sea ice extent for December 2017 was 9.34 million square kilometers (3.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

In the Southern Hemisphere, sea ice for December 2017 averaged 9.34 million square kilometers (3.61 million square miles) and was the fourth lowest in the satellite record. Sea ice extent was far below average in the eastern Weddell Sea, but above average in the northwestern Weddell Sea. The East Antarctic coastline had near-average ice extent. As the Southern Hemisphere entered into the summer months, sea ice declined steeply. Temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average in Dronning Maud Land and the northern Ross Sea, and generally lower than average over the ice sheet. Near-average temperatures have prevailed over the fringing Southern Ocean. Pressures were slightly above average over the continent and below average in the surrounding ocean. Consistent with this pattern, the Southern Annular Mode index, a measure of the strength of westerly winds, was moderately positive for December.

Further reading

Walsh, J. E., F. Fetterer, J. S. Stewart, and W. L. Chapman. 2016. A database for depicting Arctic sea ice variations back to 1850. Geographical Review. doi: 10.1111/j.1931-0846.2016.12195.x.

Freezing in the dark

Rapid expansion of the Arctic sea ice cover is the norm for October as solar input dwindles and the remaining heat in the upper ocean is released upwards, warming the lower atmosphere and escaping to space. Because of late season growth, the seasonal Antarctic maximum we previously reported as occurring on September 15 was exceeded, with a new maximum set on October 11 and 12. This is the second-lowest and second-latest seasonal maximum extent in the satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2017 was6.71 million square kilometers (2.60 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for October 2017 was 6.71 million square kilometers (2.60 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for October 2017 averaged 6.71 million square kilometers (2.60 million square miles), the fifth lowest in the 1979 to 2017 satellite record. This was 1.64 million square kilometers (633,000 square miles) below the 1981 to 2010 average and 820,000 square kilometers (317,000 square miles) above the record low October extent recorded in 2012. By the end of October, extent remained below average throughout most of the Arctic except within the Laptev Sea, which is fully ice covered. Ice growth over the month was most prominent within the Beaufort, East Siberian, and Laptev Seas and within Baffin Bay. In the Chukchi, Kara, and Barents Seas, the rate of ice growth was slower. Ice extent also remains far below average in the East Greenland Sea.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of November 2, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted 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.

Figure 2a. The graph above shows Arctic sea ice extent as of November 2, 2017 along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted 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 Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for October 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for October 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2c. This plot shows Arctic air temperatures as a function of both height and latitudes. Above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) high in the atmosphere. Colors indicate temperatures in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2c. This plot shows Arctic air temperatures as a function of height and latitudes. Above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) altitude. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Ice growth during October 2017 averaged 94,200 square kilometers (36,000 square miles) per day. This was 5,100 square kilometers (2,000 square miles) per day faster than the average rate of ice growth for the month. Total ice extent for the month remains more than 2 standard deviations below the 1981 to 2010 average.

October air temperatures at 925 hPa (about 3,000 feet above sea level) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over most of the Arctic Ocean and up to 7 degrees Celsius (13 degrees Fahrenheit) above average over the East Greenland Sea. Unusually high temperatures over the East Greenland Sea appear to largely reflect the transport of warm air from Eurasia, driven by the combination of above average sea level pressure over the Kara and Barents Seas, and below average pressure over the North Atlantic and Greenland. Elsewhere, above average near surface air temperatures reflect in part the exchange of heat from the ocean to the atmosphere as the ocean cools and sea ice forms, such as within the Chukchi Sea. A plot of temperatures as a function of both height and latitudes shows that the above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) high in the atmosphere.

October 2017 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2017 shows a decline of 9.3 percent per decade.

Figure 3. Monthly October ice extent for 1979 to 2017 shows a decline of 9.3 percent per decade.

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

The linear rate of sea ice decline for October is 77,600 square kilometers (30,000 square miles) per year, or 9.3 percent per decade relative to the 1981 to 2010 average. While this appears as an increase in the rate of October ice retreat compared to the trend reported last year, it is not a climate signal but is rather largely a result of using a different averaging method to derive the monthly average sea ice extent values (see below).

Effects of snow salinity on CryoSat-2 ice freeboard estimates

Figure 4. This schematic illustrates how salinity shifts the source of the radar signature in the icepack.

Figure 4. This schematic illustrates how salinity shifts the source of the radar signature in the icepack. Ice thickness can be over-estimated by radar satellites (CryoSat-2) when snow conditions are more saline.

Credit: V. Nandan
High-resolution image

After the end of sea ice melt season, the ocean cools and new sea ice forms. The ice crystals that form expel salt into the water. Some of this salt, or brine, is also expelled upwards to the surface of the ice or into snow that has fallen since the ice formed. The brine is then wicked upwards into the snowpack, leading to a slightly saline snowpack, ranging from 1 to 20 parts per thousand (standard seawater is about 35 parts per thousand). This saline snow is a strong reflector of radar energy.

A recent study led by the Cryosphere Climate Research Group at the University of Calgary investigated the impact of snow salinity on retrieving sea ice thickness from radar altimeters, such as CryoSat-2. The study shows that the snow layers observed over much of the Arctic’s first-year ice are salty enough to reflect the radar pulse from CryoSat-2, a radar altimeter used to measure sea ice thickness and ice sheet elevation. They calculate that a correction factor could compensate for this effect, and improve sea ice thickness measurements. While snow salinity is important, other factors, such as surface roughness and ice density also contribute to uncertainties in ice thickness, and they can potentially cancel each other out. Continued comparisons to observed thickness data is crucial to better quantify these uncertainties.

Antarctica’s double-humped sea ice maximum

Figure 5. This graph shows the first and second peaks in extent during the 2017 Antarctic sea ice freeze up.

Figure 5a. This graph shows the first and second peaks in extent during the 2017 Antarctic sea ice freeze up. The extent line for the year 2002 is also shown and has a similar pattern to 2017. Sea Ice Index data. About the data

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

Figure 5b. This map shows Antarctic sea ice concentration on October 31, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2)||Credit: Institute of Environmental Physics, University of Bremen|High-resolution image

Figure 5b. This map shows Antarctic sea ice concentration on October 31, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scanning Radiometer 2 (AMSR2).

Credit: Institute of Environmental Physics, University of Bremen
High-resolution image

In our last post, we noted that Antarctic sea ice may have reached its maximum extent for the year on September 15, at 17.98 million square kilometers (6.94 million square miles). However, after two weeks of decline, extent increased again reaching a second and final maximum of 18.03 million square kilometers (6.96 million square miles) on October 11 and 12. This is tied with 2002 for the latest maximum on record and is the second lowest Antarctic maximum extent in the satellite data record, slightly higher than 1986. Interestingly, 2002 had a similar Bactrian maximum pattern.

The Maud Rise polynya (or Weddell Sea polynya) continues to be a significant feature of the sea ice cover near 5°E longitude and 65°S. The feature appeared around September 13 and grew to its approximate current extent by September 17. Its current size remains about 30,000 square kilometers (12,000 square miles).

Winds and ocean temperatures continue to drive Antarctic sea ice variability. Since there is no land boundary to the north of the Antarctic continent, sea ice in the Southern Hemisphere is free to expand toward the equator until it reaches water temperatures that are high enough to melt sea ice. As a result, changes in winds or ocean temperatures can have a large influence on the amount of sea ice year to year. Changes in winds related to the positive phase of the Southern Annular Mode (SAM) appear to explain the positive trend in total Antarctic sea ice extent. When the SAM is in a positive phase during austral summer, stronger than average westerly winds blow around the Antarctic continent, and sea ice is pushed both westward and slightly northward due to the Coriolis effect. In addition, below average sea surface temperatures persist through the summer and lead to increased sea ice growth the following autumn, while the negative phase precedes higher sea surface temperatures and reduced sea ice growth. A new study suggests the negative SAM mode during 2016/2017 austral summer largely explained the record minimum Antarctic sea ice extent observed in March 2017.

Revised computation of the monthly mean extent

Figure 6. This chart compares the monthly October Arctic sea ice extents generated from the old (black dashed line) and the new (solid black line) averaging method.

Figure 6. This chart compares the monthly October Arctic sea ice extents generated from the old (black dashed line) and the new (solid black line) averaging method. Sea Ice Index data. About the data

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

We have updated the way the monthly average sea ice extent is calculated in the NSIDC Sea Ice Index, the source for our sea ice extent estimates. The monthly average total extent (and area) are now computed as an average of the daily values over the month. Historically, the monthly mean sea ice extent has been calculated based on the monthly mean averaged sea ice concentration field. While there is a rationale for both approaches, the new method is more intuitive and eliminates unusual and unexpected results in months when there is rapid ice growth and retreat. Most of the new monthly mean extents are smaller than the previous values with a mean extent difference between -0.45+0.24 and -0.23+0.16 million square kilometers for the Arctic and Antarctic, respectively. The largest differences for the Arctic occur during the month of October due to the rapid ice growth rates typical at that time of year, with the largest difference of -1.20 million square kilometers in October 2012. Changes in rankings and trends were much smaller because the new method tends to affect all years of a given month in a similar manner. October is also the month with the largest trend difference, increasing in magnitude from -7.4 percent per decade to -9.3 percent per decade. Changes in Arctic trends for other months are much smaller.

Similarly, in the Antarctic, differences in averaging methods results in the largest changes during the month of December when the ice cover is rapidly receding. The largest difference of -1.27 million square kilometers occurs in December 1981. The largest changes in the trends are for January and December with a change in value from +2.7 to +3.5 and +1.2 to +1.9 percent per decade, respectively. For more detailed information on the impacts of the revised averaging methods on trends and rankings, please see NSIDC Special Report 19.

Further reading

Nandan, V., T. Geldsetzer, J. Yackel, M. Mahmud, R. Scharien, S. Howell, J. King, R. Ricker, and B. Else. 2017. Effect of snow salinity on CryoSat-2 Arctic first-year sea ice freeboard measurements: Sea ice brine-snow effect on CryoSat-2. Geophysical Research Lettersdoi:10.1002/2017GL074506.

Doddridge, E. W. and J. Marshall. 2017. Modulation of the seasonal cycle of Antarctic sea ice extent related to the Southern Annular Mode. Geophysical Research Letters, 44, 9761–9768. doi: 10.1002/2017GL074319.

Windnagel, A., M. Brandt, F. Fetterer, and W. Meier. 2017. Sea Ice Index Version 3 Analysis. NSIDC Special Report 19. https://nsidc.org/sites/nsidc.org/files/files/NSIDC-special-report-19.pdf.

Arctic sea ice at minimum extent

On September 13, Arctic sea ice appears to have reached its seasonal minimum extent of 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the 38-year satellite record. The overall rate of ice loss this summer was slowed by a persistent pattern of low sea level pressure focused over the central Arctic Ocean.

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 13, 2017 was 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the satellite record. The orange line shows the 1981 to 2010 average extent for that day.

Figure 1. Arctic sea ice extent for September 13, 2017 was 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the satellite record. The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On September 13, 2017, sea ice extent reached an annual minimum of 4.64 million square kilometers (1.79 million square miles). This was 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 median extent for the same day, and 1.25 million square kilometers (483,000 square miles) and 500,000 square kilometers (193,000 square miles) above the 2012 and 2016 extents for the same day, respectively.

During the first two weeks of September, the ice edge continued to retreat in the Chukchi, East Siberian, and Kara Seas, whereas it slightly expanded in the Beaufort and Laptev Seas. The ice edge remains far to the north of its average position in the Chukchi Sea. The Northern Sea Route is largely open; Amundsen’s Northwest Passage (the southern route) has up to 50 percent ice cover in some places, though as noted in our last post, ships have successfully navigated through the southern route with icebreaker assistance. The northern Northwest Passage route, entered from the west via McClure Strait, remains choked by consolidated, thick, multi-year ice.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, 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 image shows average sea level pressure over the Arctic Ocean for the period of September 1 to 16, 2017.

Figure 2b. This image shows average sea level pressure over the Arctic Ocean for the period of September 1 to 16, 2017.

Credit: NSIDC courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

The date of the minimum ice extent for 2017 was two days earlier than the average minimum date of September 15. The earliest annual sea ice minimum in the satellite record occurred on September 5 in the years 1980 and 1987, and the latest on September 23, 1997.

As is typical of this time of year when the solar radiation received at the surface is quickly waning, the rate of ice loss slowed during the first half of September. Ice retreat from the beginning of September until the minimum averaged 25,300 square kilometers (9,770 square miles) per day, slightly faster than the 1981 to 2010 average for the same period of 22,800 square kilometers (8,800 square miles) per day.

The pattern of low sea level pressure over the central Arctic Ocean that persisted through this summer and inhibited summer ice loss has broken down. For the first half of September, the pattern has instead been one of above-average sea level pressure centered over the Barents Sea and extending across part of the Arctic Ocean (Figure 2b). Corresponding air temperatures at the 925 hPa level (about 2,500 feet above sea level) were above average over most of the Arctic Ocean. Above average temperatures over some parts of the Arctic Ocean likely reflect heat transfer to the atmosphere from areas of open water, hence cooling the ocean.

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

Table 1.  Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 Sept. 17
2 2016
2007
4.14
4.15
1.60
1.60
Sept. 10
Sept. 18
4 2011 4.34 1.67 Sept. 11
5 2015 4.43 1.71 Sept. 9
6 2008 4.59 1.77 Sept. 19
7 2010 4.62 1.78 Sept. 21
8 2017 4.64 1.79 Sept. 13
9 2014 5.03 1.94 Sept. 17
10 2013 5.05 1.94 Sept. 13

Effects of seasonal ice retreat in the Beaufort and Chukchi Seas

Figure 3. This chart shows combined sea ice extent in the Chukchi and Beaufort Seas from August 15 to October 7 for the years 2006 to 2016, including the extent so far for 2017. The colored dots show the day the minimum occurred in the region during a specific year. ||Credit: Courtesy R. Thoman/National Weather Service Alaska Region Environmental and Scientific Services Division| High-resolution image

Figure 3. This chart shows combined sea ice extent in the Chukchi and Beaufort Seas from August 15 to October 7 for the years 2006 to 2016, including the extent so far for 2017. The colored dots show the day the minimum occurred in the region during a specific year. Data are from the Multisensor Analyzed Sea Ice Extent (MASIE) product.

Credit: Courtesy R. Thoman/National Weather Service Alaska Region Environmental and Scientific Services Division
High-resolution image

According to a report by the Alaska Dispatch News, the lack of sea ice forced walruses to the shore of Alaska’s Chukchi Sea earlier than any time on record. The lack of ice also forced biologists monitoring Alaska polar bears to cut short their spring field season. In turn, the NOAA National Weather Service Climate Prediction Center states that because of the extensive open water, air temperatures over the Beaufort and Chukchi Seas and along the North Slope of Alaska will likely be far above average through this autumn.

Rick Thoman of the National Weather Service in Fairbanks, Alaska compiled an analysis of the combined Chukchi and Beaufort Seas ice extent from the Multisensor Analyzed Sea Ice Extent (MASIE) product. MASIE is based on operational ice analyses at the U.S. National Ice Center and is archived and distributed by NSIDC. It shows that 2017 tracked near record lows for the region through much of the summer, but after mid-August the pace of ice loss slowed relative to recent years. While it appears unlikely that extent in the Beaufort and Chukchi Seas will reach a record low (set in 2012), it will still be among the four or five lowest in the MASIE record (Figure 3). Note that the range in dates for the minimum extent in the region differs from those for the Arctic as a whole and tend to be later, ranging from September 10 in 2015 to September 25 in 2007 and 2008. In other words, the Chukchi and Beaufort Seas may continue to lose ice even after the overall Arctic minimum extent is reached. From the passive microwave data (not shown), the Chukchi/Beaufort minimum has occurred as early as August 14 in 1980 to as late as October 2 in 1991.

Antarctic sea ice approaching winter maximum

Figure 4a. The graph above shows Antarctic sea ice extent as of September 17, 2017, along with daily ice extent data for four previous years.

Figure 4a. The graph above shows Antarctic sea ice extent as of September 17, 2017, along with daily ice extent data for four previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in dashed brown, 2013 in purple. 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 4b: This map shows Antarctic sea ice concentration on September 16, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2).

Figure 4b: This map shows Antarctic sea ice concentration on September 16, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2).

Credit: G. Heygster, C. Melsheimer, J. Notholt/Institute of Environmental Physics, University of Bremen
High-resolution image

Following the record low summer minimum extent in March, Antarctic sea ice extent is now nearing its winter maximum. This will likely be among the five lowest winter extents in the satellite era. As of mid-September, Antarctic ice extent was just under 18 million square kilometers (7 million square miles), which is approximately half a million square kilometers below the 1981 to 2010 median ice extent. Sea ice is below the typical extent in the Indian Ocean sector, the northern Ross Sea, and the northern Weddell Sea, and slightly above average extent in the northern Amundsen Sea region.

Between September 9 and September 17 of 2016, Antarctic sea ice lost nearly 100,000 square kilometers (38,600 square miles) of sea ice per day, and sea ice extent moved from near-average to a near-record-daily low by September 17. For the next 12 months Antarctic sea ice remained extremely low. Record low ice extents were set every day from November 5, 2016 to April 10, 2017. Extents averaged for November and December of 2016 were five standard deviations below average. No other 12-month period (September 2016 to August 2017) has had such persistently low sea ice extent. The year 1986 had near-record low extent for the winter period (June to December), but there were periods of near-average and even above-average ice extent earlier in the calendar year.

Beginning around September 2, an opening in the Antarctic sea ice pack formed north of Dronning Maud Land in the easternmost Weddell Sea (near 64°S, 5°E). By mid-September, this opening, or polynya, had grown to about 12,000 square kilometers (4,600 square miles). This feature has been observed intermittently in the Antarctic pack ice since the first satellite data became available in the 1970s. In 1974, 1975, and 1976, the polynya was much larger, averaging 250,000 square kilometers (96,500 square miles). It was absent for many years in the 1980s and 1990s. In recent years the feature has been observed sporadically and has been much smaller.

The polynya is formed when ocean currents uplift deep warm ocean water to the surface where it melts the sea ice. An oceanic plateau called the Maud Rise is responsible for forcing the vertical movement of the water. The persistence of certain atmospheric patterns, such as the southern annular mode, or SAM, is thought to play a role in driving the deep water layer against the Maud Rise.

2017 Arctic sea ice minimum animation

See the NASA animation of Arctic sea ice extent from the beginning of the melt season on March 8, 2017 to the day of the annual minimum on September 13, 2017 here.

Further reading

Gordon, A.L., Visbeck, M. and Comiso, J.C. 2007. A possible link between the Weddell Polynya and the Southern Annular Mode. Journal of Climate20(11), 2558-2571. doi:10.1175/JCLI4046.1

Holland, D.M. 2001. Explaining the Weddell Polynya–a large ocean eddy shed at Maud Rise. Science, 292(5522), 1697-1700. doi:10.1126/science.1059322.

Erratum

In Table 1, years 2014 and 2013 were both ranked ninth lowest. They should have been ninth and tenth respectively. This has been corrected.

 

 

The end of summer nears

Average sea ice extent for August 2017 ended up third lowest in the satellite record. Ice loss rates through August were variable, but slower overall than in recent years. Extensive areas of low concentration ice cover (40 to 70 percent) are still present across much of the Eurasian side of the Arctic Ocean.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2017 was 5.51 million square kilometers (2.13 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for August 2017 was 5.51 million square kilometers (2.13 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for August 2017 averaged 5.51 million square kilometers (2.13 million square miles), the third lowest August in the 1979 to 2017 satellite record. This was 1.77 million square kilometers (683,000 square miles) below the 1981 to 2010 average, and 800,000 square kilometers (309,000 square miles) above the record low August set in 2012.

Ice retreat was most pronounced in the western Beaufort Sea. A large region in the Beaufort Sea and East Siberian Sea has low concentration sea ice (40 to 70 percent). Patches of low concentration sea ice and some open water northeast of the Taymyr Peninsula are also present.

While a record low minimum extent in the Arctic is unlikely this year, the ice edge in the Beaufort Sea is extremely far north. In parts of this region, the ice edge is farther north than at any time since the satellite record began in 1979. This highlights the pronounced regional variability in ice conditions from year to year. A couple of the models that contribute to the Sea Ice Prediction Network Sea Ice Outlooks forecasted significantly less ice in the Beaufort Sea in July this year compared to average conditions.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 5, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of September 5, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted 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 image shows average sea level pressure over the Arctic for the month of August 2017.

Figure 2b. This image shows average sea level pressure in millibars over the Arctic for the month of August 2017.

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

Over the month, low atmospheric pressure prevailed over much of the Arctic Ocean, centered over the northern Beaufort Sea (Figure 2b). This helped to push the ice edge in that region northward. Summers dominated by low pressure, as has been the case for 2017, are generally not conducive to ice loss. Low pressure brings generally cool conditions and the cyclonic (counterclockwise) winds help spread the ice over a larger area. However, it appears that strong individual storms, such as the intense summer cyclone of 2012, may break up the ice and mix warm ocean waters into the sea ice, contributing to ice loss.

August 2017 compared to previous years

Figure 3. Monthly August ice extent for 1979 to 2017 shows a decline of 10.48 percent per decade.

Figure 3. Monthly August ice extent for 1979 to 2017 shows a decline of 10.5 percent per decade.

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

The linear rate of decline for August 2017 is 76,300 square kilometers (29,000 square miles) per year, or 10.5 percent per decade. The daily ice loss rate was variable over the month, slowing considerably during the middle and end of the month. Overall, the loss rate during August 2017 was slower than recent years, particularly 2012, when extent decreased rapidly during the first half of the month after a the passage of a strong storm.

A report on the Northwest Passage

Figure 4a. This shows the route of the Crystal Serenity (yellow line) overlaid on a map of ice cover in the Northwest Passage region.

Figure 4a. This shows the route of the Crystal Serenity (yellow line) overlaid on a map of ice cover in the Northwest Passage region for September 5, 2017.

Credit: Canadian Ice Service Daily and Regional Ice Charts
High-resolution image

Figure 4b. This chart shows sea ice area in the Parry Channel region of the Canadian Archipelago from April 30 to November 26 for the years 2010 (magenta), 2011 (dashed green), 2014 (blue green), 2016 (purple, and 2017 (red). The black line shows the 1980 to 2010 long-term average. ||Credit: Environment and Climate Change Canada|

Figure 4b. This chart shows sea ice area in the Parry Channel region of the Canadian Archipelago from April 30 to November 26 for the years 2010 (magenta), 2011 (dashed green), 2014 (blue green), 2016 (purple), and 2017 (red). The black line shows the 1981 to 2010 long-term average.

Credit: Environment and Climate Change Canada
High-resolution image

Figure 4c. This photo shows sea ice conditions along the route of the Crystal Serenity.||Credit: C. Haas|High-resolution image

Figure 4c. This photo shows sea ice conditions along the route of the Crystal Serenity.

Credit: C. Haas, York University
High-resolution image

Of particular interest each year are the ice conditions in the Northwest Passage. Our colleagues, Stephen Howell and Michael Brady of the Climate Research Division at Environment and Climate Change Canada, provided a status update based on sea ice charts produced by the Canadian Ice Service.

As of August 28, the northern route of the Northwest Passage was blocked by high concentration ice at the western (Parry Channel) entrance (Figure 4a), but overall extent in the passage is still tracking below the 1981 to 2010 average (Figure 4b). The record low seasonal extent in the northern route was in 2011. Low ice years in the northern route are typically the result of early breakup associated with above-average sea level pressure over the Beaufort Sea and Canadian Basin; this pattern tends to displace ice away from the western entrance. Conversely, low sea level pressure over the Beaufort Sea, such as seen this summer, packs ice up against the western entrance. It is unlikely the northern route will open in this year. Ice concentrations are much milder in the southern route (Amundsen’s Passage) but some ice still blocks the eastern part of that passage. This is primarily first year ice that may melt out in the coming weeks. During low ice summers, thick multi-year ice originating from the Arctic Ocean is typically advected into the channels of both the northern and southern routes, representing a significant hazard to transiting ships.

The Crystal Serenity luxury cruise ship, accompanied by an icebreaker, is attempting a repeat of last year’s cruise through the passage. Professor Christian Haas of York University in Toronto, who is providing sea ice expertise on board the ship, sent us a first-hand account of conditions:

“On August 29 and 30, we encountered some high concentration ice, up to 90 percent, just before entering Bellot Strait. The ice was mostly first-year ice, with about 30 percent multi-year ice having thicknesses greater than 2 meters (6.5 feet). Due to the relatively severe ice conditions, we were supported by the Canadian Coast Guard icebreaker Des Groseilliers, which helped clear some ice on our route into Franklin Strait. Overall, ice conditions have been much more severe than during the first transit of the Northwest Passage of the Crystal Serenity in 2016, when no ice was encountered at all.”

Figure 4c shows conditions along the route. The ship’s latest position is available at the cruise’s blog.

Also of note, the Finnish icebreaker MSV Nordica, set a new record for the earliest transit through the passage on July 29, traveling 10,000 kilometers (6,000 miles) in 24 days.

On the other side of the Arctic, the Northeast Passage (or Northern Sea Route) along the coast of Siberia appears largely open as shown by NSIDC data, though operational analysis by the U.S. National Ice Center shows some remaining ice along the coast of the Taymyr Peninsula.

A radar view of the Arctic

Figure 5. Composite image from Sentinel-1 SAR imagery for August 29, 2017 overlaid with passive microwave sea ice concentration from the JAXA AMSR2 sensor. Red/pink shades indicate regions of high (>90 percent) concentration, while green/brown shades indicate lower (~30-70 percent) concentration. Open water is in black to blue/gray shades. Open water is evident between floes of ice in the low concentration regions.

Figure 5. This figure shows a composite image from Sentinel-1 SAR imagery for August 29, 2017 overlaid with passive microwave sea ice concentration from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor. Red/pink shades indicate regions of high (more than 90 percent) concentration, while green/brown shades indicate lower (~30-70 percent) concentration. Open water is in black to blue/gray shades. Open water is evident between floes of ice in the low concentration regions.

Credit: Image from Danish Technical University, courtesy Leif Pedersen and Roberto Saldo
High-resolution image

The passive microwave satellite imagery that NSIDC uses is ideal for showing long-term changes in sea ice because it provides a continuous record extending back to 1979. Its drawback is low spatial resolution. Satellite radar images, though more limited in spatial and temporal coverage, provide a more detailed picture of the ice cover. A daily composite of images from the European Space Agency’s Sentinel-1 satellite, with a synthetic aperture radar (SAR) instrument, shows substantial open water well within the ice pack, north of 80° N latitude.

Which August will we get?

Average sea ice extent for July 2017 ended up fifth lowest in the satellite record. This reflects weather conditions that were not favorable for ice loss. It will be important to monitor August 2017, as weather conditions and storm events during this month have been closely related to the seasonal minimum sea ice extent in the recent years.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2017 was 8.2 million square kilometers (3.2 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for July 2017 was 8.21 million square kilometers (3.17 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for July 2017 averaged 8.21 million square kilometers (3.17 million square miles), the fifth lowest July in the 1979 to 2017 satellite record. The average July extent was 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 long-term average, and 270,000 square kilometers (104,000 square miles) above the previous record low July set in 2011. July 2017 tracked 250,000 square kilometers (97,000 square miles) above the July 2012 extent and 20,000 square kilometers (7,700 square miles) above the July 2007 extent.

Ice extent was lower than average over most of the Arctic, particularly on the Pacific side where the ice retreated throughout July in the Beaufort, Chukchi, and East Siberian Seas. In the eastern Beaufort Sea on the other hand, extent slightly expanded during July. This may relate to the cyclonic (counterclockwise) pattern of winds favoring the drift of sea ice into the region.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted 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

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted 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
High-resolution image

Figure 2b. The plot shows differences from average for Arctic air temperatures at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. The plot shows Arctic air temperature differences relative to the 1981 to 2010 long-term average at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

The air temperature pattern over the Arctic was rather complex in July. Temperatures were above average over Alaska, extending into the Beaufort Sea (1 to 2 degrees Celsius or 2 to 4 degrees Fahrenheit) and the Kara and Barents Seas (2 to 4 degrees Celsius or 4 to 7 degrees Fahrenheit). By contrast, temperatures were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) lower than average over Greenland, East Central Siberia, and the Laptev Sea. The air pressure pattern at sea level was dominated by a broad area of low pressure covering most of the Arctic Ocean, with the lowest pressures centered just south of the Pole and west of the date line. Another locus of low pressure was centered over the southern Canadian Arctic Archipelago.

A cyclonic circulation over the central Arctic Ocean is generally viewed as unfavorable for rapid summer ice loss. Ice loss rates tend to be higher when the central Arctic Ocean is dominated by high pressure during summer.

July 2017 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2017 shows a decline of 7.4 percent per decade.

Figure 3. Monthly July ice extent for 1979 to 2017 shows a decline of 7.4 percent per decade.

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

The linear rate of decline for July 2017 was 72,500 square kilometers (28,000 square miles) per year, or 7.4 percent per decade.

Onset of surface melt

Figure 4. The plot on the left shows melt onset dates in day of the year (left). Warm colors indicate early melt onset and cooler colors indicate a later melt onset. The plot on the right shows departures from the average melt onset dates in number of days. Warmer colors indicate later than average melt onset and cooler colors indicate later than average melt onset.

Figure 4. The plot on the left shows the average melt onset dates in day of the year. Warm colors indicate early melt onset and cooler colors indicate a later melt onset. The plot on the right shows departures from the average melt onset dates in number of days. Warmer colors indicate later than average melt onset and cooler colors indicate earlier than average melt onset.

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

One important influence on the pace of summer sea ice retreat is the timing of the onset of surface melt. Surface melt drops the albedo, allowing more solar radiation to be absorbed at the surface. The onset of surface melt in 2017 was quite early in the Chukchi and Eastern Beaufort Seas—as much as 35 days earlier than the 1981 to 2010 average. Early melt was also seen in the Kara Sea, Baffin Bay, and Canadian Arctic Archipelago (10 to 20 days earlier than average). However, over a large portion of the Arctic Ocean’s central ice pack, melt onset was a few days later than average. Melt onset was up to ten days later than average in the polar areas at the northern extents of the Beaufort and East Siberian Seas. The spatial pattern in the timing of melt onset reflects the combination of the warm winter and early spring conditions along the edge of the pack on the Pacific side, very warm winter conditions in the Barents and Kara Sea areas, and relatively cool late spring to early summer conditions over the central Arctic Ocean.

Sea ice predictions for the 2017 minimum

Figure 5. This chart summarizes the 2017 summer September minimum forecasts from 36 different models and approaches to predicting the evolution of the Arctic pack.

Figure 5. This chart summarizes the 2017 summer September minimum forecasts from 36 different models and approaches to predicting the evolution of the Arctic pack.

Credit: SIPN/ARCUS
High-resolution image

A report released by the Sea Ice Prediction Network (SIPN), an activity of the Arctic Research Council of the United States (ARCUS), compiled 36 forecasts of September average sea ice extent that were submitted during July. Additionally, SIPN produces estimates for sea ice extent in the Alaska region and, new this year, for the Antarctic sea ice maximum (not shown). The September Arctic extent forecasts range from a new record low of 3.1 million square kilometers (1.2 million square miles) to an eleventh lowest extent of 5.5 million square kilometers (2.1 million square miles). The median of the estimates is slightly below the September 2016 value, currently the fifth lowest. A variety of methods are used to make these forecasts, ranging from coupled ice-ocean-atmospheric models to statistical approaches and heuristic guesses. NSIDC scientists Julienne Stroeve, Walt Meier, Andrew Barrett, Mark Serreze, and the late Drew Slater have regularly contributed to several separate estimations for the SIPN.

Sea ice retreat may be changing the AMOC

In the far northern Atlantic, warm water flowing northward from the tropics is cooled by the atmosphere, becomes denser, and eventually sinks to great depths. The descending water is key in driving a sub-surface and surface ocean circulation system called the Atlantic Meridional Overturning Circulation (AMOC), which is part of the global ocean conveyor belt of heat and salinity. Where the Atlantic water sinks has a very important effect on the climate of Northern Europe; the heat that the ocean loses to the atmosphere is what keeps Northern Europe quite warm relative to its latitude. For example, Amsterdam is at the same latitude as Winnipeg, Canada, but experiences much warmer winters.

Based on a recent modeling study, Florian Sévellec and colleagues propose that the ongoing loss of Arctic sea ice may disrupt the AMOC. The sea ice loss leads to a freshening of the northern North Atlantic and stronger heat absorption at the surface. This means that waters in the northern North Atlantic are less dense than they used to be, which has the effect of providing a cap, or lid, that may inhibit the northward flow of warm waters at the surface and the eventual sinking of these waters. The authors suggest that the Arctic sea ice decline may help to explain observations suggesting that the AMOC may be slowing down, and why there is a regional minimum in warming (sometimes called the Warming Hole) over the subpolar North Atlantic.

Further reading

Sea Ice Prediction Network. “2017: July Report.” Arctic Research Council of the United States. https://www.arcus.org/sipn/sea-ice-outlook/2017/july.

Sévellec, F., A. V. Fedorov, and W. Liu. 2017. Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation. Nature Climate Change, doi:10.1038/nclimate3353.

Arctic ice extent near levels recorded in 2012

Contrasting with the fairly slow start to the melt season in May, June saw the ice retreat at a faster than average rate. On July 2, Arctic sea ice extent was at the same level recorded in 2012 and 2016. In 2012, September sea ice extent reached the lowest in the satellite record. As a new feature to Arctic Sea Ice News and Analysis, NSIDC now provides a daily updated map of ice concentration in addition to the daily map of ice extent.

Overview of conditions

Figure 1. Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles).

Figure 1. Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles), the sixth lowest in the 1979 to 2017 satellite record. The average June 2017 extent was 900,000 square kilometers (348,000 square miles) below the 1981 to 2010 long-term average, and 460,000 square kilometers (178,000 square miles) above the previous record low set in 2016.

Continuing the pattern seen in May, sea ice extent at the end of the month remained below average in the Chukchi Sea and in the Barents Sea. Ice extent was at average levels in the Greenland Sea. Areas of low concentration ice have developed along the ice edge and coastal seas.

Based on imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Terra and Aqua satellites, summer melt ponds atop the ice cover were somewhat slow to develop. However, there is now widespread melt pond coverage in the Canadian Archipelago and the Laptev and East Siberian Seas. Data from the Advanced Microwave Scanning Radiometer 2 (AMSR-2) instrument analyzed by the University of Bremen, as well as MODIS imagery, indicate that melt ponds have also developed over the Central Arctic Ocean. Researchers in Dease Strait in Northern Canada have observed melt ponds forming about two weeks earlier than average. Melt ponds are important as they decrease the albedo or reflectivity of the ice surface, which hastens further melt.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 4, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, 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.

Figure 2. The graph above shows Arctic sea ice extent as of July 4, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, 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
High-resolution image

The rate of decline in ice extent was fairly steady through the month, and the average rate of decline of 81,800 square kilometers (31,600 square miles) per day was slightly faster than the 1981 to 2010 long-term average of 56,300 square kilometers (21,700 square miles) per day. On July 2, extent was the same as that recorded in 2012 and 2016. The year 2012 ended up with the lowest September extent in the satellite record.

June air temperatures were modestly above average (1 to 3 degrees Celsius or 2 to 5 degrees Fahrenheit) in a band spanning the Arctic Ocean roughly centered along the date line and the prime meridian. This contrasts with below-average temperatures over the eastern Beaufort Sea and Canadian Arctic Archipelago and the Barents and Laptev Seas (1 to 3 degrees Celsius, 2 to 5 degrees Fahrenheit). Atmospheric pressures at sea level were below-average over the Kara Sea and extending north of the Laptev Sea.

June 2017 compared to previous years

Figure 3. Monthly June ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

Figure 3. Monthly June ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

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

The linear rate of decline for June is 44,300 square kilometers (17,100 square miles) per year, or 3.7 percent per decade.

Ice thickness

Figure 4. Figure 4. This figure shows that sea ice thicknesses for May 2017 were below the 2000 to 2015 average over most of the Arctic Ocean (areas in blue) except for the region north and west of the Svalbard archipelago (areas in red). ||Credit: University of Washington Pan-Arctic Ice Ocean Modeling and Assimilation System

Figure 4. This figure shows that sea ice thicknesses for May 2017 were below the 2000 to 2015 average over most of the Arctic Ocean (areas in blue) except for the region north and west of the Svalbard archipelago (areas in red).

Credit: University of Washington Pan-Arctic Ice Ocean Modeling and Assimilation System
High-resolution image

The University of Washington Seattle Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) regularly produces maps of ice thickness anomalies (departures from the long-term average). PIOMAS is based on a coupled ice-ocean model that is driven by data from an atmospheric reanalysis, and also assimilates data on observed ocean conditions and ice thickness (e.g., from NASA IceBridge). The PIOMAS analysis suggests that, relative to the average over the period 2000 to 2015, ice thickness for May 2017 (when the melt season was just beginning) was below average over most of the Arctic Ocean, especially in the Chukchi Sea and north of the Canadian Arctic Archipelago. A small region with above-average ice thickness is depicted over the Atlantic side of the Arctic north and west of the Svalbard Archipelago, and in the Greenland Sea. Starting the melt season with below-average ice thickness raises the likelihood of having especially low September ice extent.

Freezing degree days and ice thickness

Figure 5. The figure shows departures from average in cumulate freezing degree days, extending from July 1 for a given year through July 1 of the next year, along with the range, 15th through 85th percentile and 30th to 70th percentile values over the base period 1981 through 2010.

Figure 5. The figure shows departures from average in cumulate freezing degree days, extending from July 1 for a given year through July 1 of the next year, along with the range, 15th through 85th percentile and 30th to 70th percentile values over the base period 1981 through 2010.

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

Cumulative Freezing Degree Days (FDD) is a simple measure of how cold it has been and for how long. Cumulative FDD is the sum of daily mean temperatures below zero from some start date. Here we start on July 1. Cumulative FDD is related to ice thickness because, on average, years with longer periods of temperatures below freezing will have more ice growth. A simple empirical model that has been used by scientists relates ice thickness to the square root of cumulative FDD.

Anomalies (departures from the average) in cumulative FDD illustrate the coldness of a given period relative to the long-term average (1981 to 2010). Figure 5 shows that most of the period from July 2016 to July 2017 was extremely mild and was milder (less cold) than both 2006 to 2007 and 2011 to 2012. September of both 2007 and 2012 ended up with very low September sea ice extent. This is consistent with below-average ice thickness seen in the PIOMAS data. Although conditions cooled in May and June, this likely had little impact on ice thickness. This is because ice in the Arctic reaches its maximum thickness earlier in the season during March or April. As noted earlier, ice retreated at a fast rate throughout June. This is likely linked to a thinner than average ice cover as seen in the PIOMAS analysis.

Sudden Antarctic sea ice decline in late 2016

A slight decrease in the rate of sea ice growth at the end of June brought Antarctic sea ice extent back to daily record lows. Sea ice extent in the Bellingshausen, eastern Amundsen, and western Ross Seas was below average.

Our post on December 2016 ice conditions highlighted a precipitous drop in Antarctic sea ice extent in the Weddell and Ross Sea sectors during September, October, and November of 2016. A recent study by John Turner and colleagues links this pattern of sea ice decline to a series of strong storms, marked by long periods of warm winds from the north. These changing weather conditions are associated with large shifts in the Southern Annual Mode index (SAM index).

Further reading

Turner, J., T. Phillips, G. J. Marshall, J. S. Hosking, J. O. Pope, T. J. Bracegirdle, and P. Deb. 2017. Unprecedented springtime retreat of Antarctic sea ice in 2016, Geophysical Research Letters, 44, doi:10.1002/2017GL073656.