The longest day of summer has come and gone, and summer melt is in full swing, with the pace of ice loss overall about average for this time of year. Arctic sea ice extent for June was not exceptionally low compared to other recent years. Antarctic sea ice extent continues to track at record low values.

Overview of conditions

Figure 1a. Arctic sea ice extent for June 2023 was 10.96 million square kilometers (4.23 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of July 5, 2023, along with daily ice extent data for four previous years and the record low year. 2023 is shown in blue, 2022 in green, 2021 in orange, 2020 in brown, 2019 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Average Arctic sea ice extent during June 2023 was 10.96 million square kilometers (4.23 million square miles) (Figure 1a), the thirteenth lowest June in the satellite record. The average extent was 800,000 square kilometers (309,000 square miles) below the 1981 to 2010 average and 550,000 square kilometers (212,000 square miles) above the record low June extent, which occurred in 2016.

Through much of June 2023, extent declined faster than the 1981 to 2010 average (Figure 1b). On average, based on the 1981 to 2010 mean, about 1.69 million square kilometers (653,000 square miles) of ice is lost in June, roughly the size of Alaska. This summer, 2.30 million square kilometers of ice melted (880,000 square miles). In regions which normally lose sea ice this time of year, the rate of ice loss was faster than average. This includes the Beaufort, Chukchi, Laptev, Kara and East Greenland Seas. In the Sea of Okhotsk and the Bering and Barents Seas, where ice retreat generally starts before June, the ice loss has been slower than average. At the end of June, total sea ice extent was below that in 2022, but higher than in 2019 and 2021.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for June 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for June 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

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

Air temperatures at the 925 millibar level (approximately 2,500 feet above the surface) over the Arctic Ocean were mixed (Figure 2a). Above average temperatures of 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) were found just off the coast in the Laptev Sea, the southern Beaufort Sea off the coast of Canada, and in the East Greenland Sea and stretching towards Svalbard. North of Alaska and in the East Siberian Sea, temperatures were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average.

Below-average sea level pressure dominated Eurasia in June, with low pressure extending over much of the Arctic Ocean (Figure 2b). Coupled with above-average sea level pressure over Scandinavia, this pressure pattern fostered relatively cold Arctic air reaching Novaya Zemlya and the coastal areas of the Kara Sea, resulting in temperatures just slightly below average for this time of year.

June 2023 compared to previous years

Figure 3. Monthly June sea ice extent for 1979 to 2023 shows a decline of 3.8 percent per decade.

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

The downward linear trend in Arctic sea ice extent in June over the 45-year satellite record is 44,300 square kilometers (17,100 square miles) per year, or 3.8 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, June has lost 1.99 million square kilometers (768,000 square miles) of ice. This is roughly equivalent to the size of Mexico.

An update on sea ice age

Figure 4. This map shows sea ice age for the week of June 25 to July 1, 2023. Dark blue represents up to one-year-old ice, light blue represents one- to two-year-old ice, green represents two- to three-year-old ice, orange represents three- to four-year-old ice, and red represents ice more than four years old.

Credit: Data and images are from NSIDC EASE-Grid Sea Ice Age, Version 4 (Tschudi et al., 2019a) and Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1.
High-resolution image

An update of sea ice age reveals extensive areas of first-year ice extending far north from the Siberian coast. While first-year ice is generally thinner and more prone to melt completely than older ice, the extensive first year ice located in high northern latitudes may not melt out completely. An area of multiyear ice, much of it 4+-years old residing in the Beaufort Sea region, will likely survive the summer melt season.

Solar geoengineering studies highlight the urgent need to limit global warming to 1.5 degrees Celsius

Figure 5. This figure shows interactions potentially resulting in residual changes in the polar regions under global Stratospheric Aerosol Injection (SAI), relative to a world at the same global mean temperature without SAI. The figure does not show the first order effect of SAI, which is to cool the planet and reverse the effects of climate change, but only the residual changes. This is a simplified version of the full figure in Duffey et al. (2023). See the full figure for individual studies supporting each link and the definitions of “radiative” and “dynamic” effects. Where studies disagree on the sign of a change, the number supporting the statement in the box is indicated in brackets. Where interactions have opposite impacts on residual changes, this is indicated by color coding.

Credit: Alistair Duffey
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As new studies come out suggesting that the Arctic Ocean may witness its first ice-free summer by the 2030s, solar geoengineering studies have been exploring the potential benefits and pitfalls of reducing incoming sunlight and thus slowing Arctic warming. A review paper co-led by NSIDC scientist Julienne Stroeve explored the impacts of stratospheric aerosol injection on polar climate, considering impacts of both local and global injection of reflective sulfate aerosols into the stratosphere.

Without local injection of aerosols in the Arctic, cooling will not be as effective. However, any consideration of adding aerosols to the stratosphere to reduce incoming sunlight must be balanced by potential impacts on other aspects of the climate system, such as precipitation. If aerosols were only injected into the Arctic for example, drying in Northern Hemisphere lower latitude regions may occur. Furthermore, since the Arctic is dark or mostly dark for up to half of the year, the direct radiative effects of aerosol injection (i.e. blocking of sunlight) will be seasonally dependent. However, stratospheric heating from aerosol injection during the dark period may result in winter-time warming over high-latitude areas.

There are also potential impacts on weather and ocean circulation patterns (Figure 5). This could include more melting from the Antarctic ice shelves, thereby increasing Antarctic’s contribution to sea level rise. Atmospheric responses must be viewed with caution as the sensitivity of Arctic to changes in atmospheric circulation in climate models used for these types of assessments is not realistically simulated.

Antarctic extent remains low

Figure 6a. Antarctic sea ice extent for June 2023 was 11.02 million square kilometers (4.25 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 6b. This plot shows the departure from average sea level pressure in the Antarctic in millibars for June 1, 2023 to June 30, 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

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

The total ice extent in the Antarctic is continuing to track at extreme record low levels, with departures from the long-term average of more than four standard deviations. Sea ice extent is below average everywhere except in the northern Amundsen Sea where it is more extensive than average (Figure 6a). In the Indian Ocean sector, ice extent is near average to slightly below.

The dramatically slower pace of ice growth through the 2023 autumn and early winter is a topic of intense research. Among the most likely causes are warmer ocean conditions in the polar water layer. This layer of colder, slightly less saline seawater is usually at or very near the freezing point. A small temperature increase, from mixing upward from deeper ocean layers or from warmer ocean surface water to the north, could slow the formation of new sea ice during autumn and winter. Under typical conditions, the polar water, a layer of several tens of meters thickness in the sea ice regions of both poles, is both slightly fresher and less dense than the underlying ocean waters, which leads to strong stratification of the topmost waters. However, if warm ocean water from just north of the surface extent of the cold water has been mixed into the polar water, it reduces this density contrast, and this reduces the stratification and allows warmth to more easily mix upward from below, further increasing the heat in the upper ocean layer and prolonging the period of reduced ice growth.

A further contributing factor for the southern Bellingshausen Sea region is the persistently strong and eastward position of the Amundsen Sea Low. This is driving warm winds southward along the western Peninsula, and across the Peninsula (Figure 6b), in both cases suppressing ice growth, and moving ice in the northwestern Weddell eastward.

Trying to measure sea ice during a record low ice cover year of the Antarctic

Figure 7. This photo shows the Ku- and Ka-band radar being deployed over newly forming sea ice off the coast of the Antarctic Peninsula near Rothera Station.

Credit: Vishnu Nandan, University of Manitoba
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The Antarctic Peninsula is the fastest warming region in the southern hemisphere, and this year its western coast is experiencing particularly low sea ice extent, contributing to the record low extent for the Antarctic as a whole. As part of a joint project between the University of Manitoba and a United Kingdom-led Drivers and Effects of Fluctuations in sea Ice in the ANTarctic (DEFIANT) project, Vishnu Nandan and Robbie Mallett from the University of Manitoba are spending the winter at the UK’s Rothera Base near the Peninsula where they are monitoring thin ice cover with a crane-mounted dual-frequency radar. This instrument mimics satellite-mounted radars such as CryoSat-2, Ka-band Altimeter (AltiKa), and the European Space Agency’s forthcoming Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission. It was previously deployed on the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019 and 2020.

By scanning different ice types from a range of heights, the team’s previous surface-based observations are now being contextualized with regard to airborne and satellite platforms. Over the rest of the winter, Nandan and Mallett will perform sled-based transects of sea ice with the radar, investigating snow properties and their contribution to uncertainties in satellite-estimates of sea ice thickness. Snow remains one of the largest contributors in this respect, and results of DEFIANT’s field campaigns will provide valuable knowledge ahead of the European Space Agency CRISTAL’s anticipated launch in 2027.

Further reading

Duffey, A., P. Irvine, M. Tsamados, and J. Stroeve. 2023. Solar geoengineering in the polar regions: A review. Earth’s Future, 11, e2023EF003679. doi:10.1029/2023EF003679

Kim, Y. H., S. K. Min, N. P. Gillett, et al. 2023. Observationally-constrained projections of an ice-free Arctic even under a low emission scenario. Nature Communications. doi:10.1038/s41467-023-38511-8

Tschudi, M., W. N. Meier, and J. S. Stewart. 2019. Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/2XXGZY3DUGNQ

Topál, D., and Q. Ding. 2023. Atmospheric circulation-constrained model sensitivity recalibrates Arctic climate projections. Nature Climate Change. doi:10.1038/s41558-023-01698-1

The seasonal decline in Arctic sea ice extent was moderate through much of May before picking up pace over the last few days of the month. Meanwhile, Antarctic sea ice extent remained far below previous satellite-era record lows for this time of year.

Overview of conditions

Figure 1a. Arctic sea ice extent for May 2023 was 12.83 million square kilometers (4.95 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of June 4, 2023, along with daily ice extent data for four previous years and the record low year. 2023 is shown in blue, 2022 in green, 2021 in orange, 2020 in brown, 2019 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Average Arctic sea ice extent during May 2023 was 12.83 million square kilometers (4.95 million square miles) (Figure 1a), the thirteenth lowest May in the satellite record. The average extent was 460,000 square kilometers (178,000 square miles) below the 1981 to 2010 average and 910,000 square kilometers (351,000 square miles) above the record low May extent, which occurred in 2016.

Through much of May, extent declined slightly slower than the 1981 to 2010 average (Figure 1b). From May 1 to May 24, extent dropped 963,000 square kilometers (372,000 square miles), compared to 1.12 million square kilometers (432,000 square miles) over the same interval in the 1981 to 2010 average. However, during the last week of the month, the rate of ice loss increased. Overall, the Arctic lost 452,000 square kilometers (175,000 square miles) of ice from May 24 to May 31, compared the 1981 to 2010 average of 279,000 square kilometers (108,000 square miles) during the same interval. The late increase in extent loss dropped the extent below the interdecile range after spending most of the month just above the lower part of the interdecile range.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for May 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

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

Air temperatures at the 925 millibar level (approximately 2,500 feet above the surface) were 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) below average over much of the Arctic Ocean for the month as a whole, except the Barents, Kara, and Beaufort Seas, where temperatures were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above average (Figure 2a). Hudson Bay was also warmer than average, especially in the northwest part of the bay where temperatures were up to 8 degrees Celsius (14 degrees Fahrenheit) above average. Most of the Arctic Ocean in May was dominated by below average sea level pressure, as much as 10 millibars below average north of the Laptev Sea (Figure 2b). This type of pattern is known to be generally associated with below average air temperatures over the Arctic Ocean. By contrast, the unusually warm conditions over Hudson Bay can be linked to high sea level pressure (an anticyclonic circulation).

May 2023 compared to previous years

Figure 3. Monthly May sea ice extent for 1979 to 2023 shows a decline of 2.4 percent per decade.

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

The downward linear trend in Arctic sea ice extent in May over the 45-year satellite record is 32,300 square kilometers (12,500 square miles) per year, or 2.4 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, May has lost 1.42 million square kilometers (548,000 square miles) of ice. This is roughly equivalent to four times the size of Germany.

Antarctic extent remains low

Figure 4a. The graph above shows Antarctic sea ice extent as of June 4, 2023, along with daily ice extent data for four previous years and the record high year. 2023 is shown in blue, 2022 in green, 2021 in orange, 2020 in brown, 2019 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 4b. Antarctic sea ice extent for May 2023 was 8.36 million square kilometers (3.23 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

Down south, Antarctic sea ice extent is at record low levels as assessed over the satellite record since 1978. The Antarctic winter is approaching, so May and June are months of large increases in extent, but this year, extent is far lower than average for May (Figure 4a). Sea ice extent was particularly low in the Bellingshausen Sea, Weddell Sea, and western Ross Sea regions; only the central Amundsen and Eastern Ross Seas were above the typical late May ice extent (Figure 4b).

In an average (1981 to 2010) May, Antarctic extent increases by 3.25 million square kilometers (1.25 million square miles). This May, the increase was only 2.87 million square kilometers (1.11 million square miles). As of May 31, sea ice extent is approximately 700,000 square kilometers (270,000 square miles) below the previous daily record lows, which occurred in in 1980, 2017, and 2019. (Please note that 1986 values are affected by a no-data period from the satellites we use).

The May 2023 sea ice extent continues the very low ice extent conditions seen throughout most of 2022, and generally low ice extents since 2016. For May 2023, weather conditions have been marked by above average air temperatures at the 925-millibar level of up to 4 degrees Celsius (7 degrees Fahrenheit) over the Weddell Sea extending over the Peninsula, and additionally a region north of Wilkes Land. Cool conditions prevailed over the Amundsen Sea, around 4 degrees Celsius below average (7 degrees Fahrenheit). Air pressure patterns for May indicate an especially strong Amundsen Sea Low (12 millibars below the 1991 to 2020 average), shifted somewhat eastward of its typical location. For 2023 to date, the conditions are much the same over the five months so far, with air temperatures up to 2 degrees Celsius above average (4 degrees Fahrenheit) over the Weddell Sea and the  Peninsula, and a 9-millibar below-average Amundsen Sea Low centered in the far southeastern Bellingshausen Sea, well to the east of its typical location.

Sea Ice Outlook begins another year

Over the past 15 years, the Sea Ice Outlook has been a community effort to improve prediction of Arctic September sea ice extent. The Outlook submissions are due June 12. The Outlook is managed by the Arctic Consortium of the United States (ARCUS) and is currently funded by the National Science Foundation.

The rate of sea ice loss for April 2023 was slow, owing to cool conditions across the ice-covered Arctic Ocean and below-average to near-average temperatures near the ice edge. Antarctic sea ice extent remained sharply below average throughout the month.

Overview of conditions

Figure 1a. Arctic sea ice extent for April 2023 was 13.99 million square kilometers (5.40 million square miles. The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of May 2, 2023, along with daily ice extent data for four previous years and the record low year. 2023 is shown in blue, 2022 in green, 2021 in orange, 2020 in brown, 2019 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

The April 2023 average Arctic sea ice extent was 13.99 million square kilometers (5.40 million square miles), tied with 2004 as the tenth lowest April in the satellite record (Figure 1a). The average monthly extent was 700,000 square kilometers (270,000 square miles) below the 1981 to 2010 average of 14.69 million square kilometers (5.67 million square miles), but 560,000 square kilometers (216,000 square miles) above the record low set in April 2019 (Figure 1b). The rate of sea ice loss through April was only 20,600 square kilometers (8,000 square miles) per day, well below the 1981 to 2010 average of 36,400 square kilometers (14,000 square miles) per day. Toward the end of the month, extent reached the lowest decile of daily extents as assessed over the satellite record. Overall, sea ice extent decreased 690,000 square kilometers (266,000 square miles) during April 2023, compared to the 1981 to 2010 average April decrease of 1.16 million square kilometers (448,000 square miles). At the end of the month, extent remained below average primarily in the Barents Sea. The ice edge is also north of its usual position over part of the Bering Sea.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for April 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

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

Air temperatures at the 925 hPa level in April were near average to below average over most of the Arctic Ocean (Figure 2a). This helps to explain the slow rate of sea ice loss during April. While temperatures were modestly above average over the Barents Sea, these areas are already largely free of sea ice. The sea level pressure pattern was characterized by fairly high pressure over most of the Arctic Ocean (Figure 2b). The clockwise winds around a separate high-pressure center over Scandinavia brought warm winds from the south over the Barents Sea, consistent with the above air average temperatures in that area. Similarly, below-average temperatures over Alaska were driven by the combination of a strong low pressure area in the Gulf of Alaska and high pressure in the Beaufort Sea, driving air generally southward from the ice-covered Arctic Ocean.

April 2023 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2023 shows a decline of 2.5 percent per decade.

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

The downward linear trend for Arctic sea ice extent in April over the 45-year satellite record is 37,000 square kilometers (14,300 square miles) per year, or 2.5 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, April has lost 1.65 million square kilometers (637,000 square miles) of ice. This is roughly equivalent to twice the size of Ukraine.

Clouds and Arctic sea ice

A new study by Sledd et al. offers evidence that as carbon dioxide levels rise, summer clouds will have an increasingly strong influence on Arctic sea surface temperatures (SSTs). This is because as the Arctic warms and sea ice retreats earlier, more solar radiation is absorbed by the upper ocean, causing the ocean to warm. Over snow- and ice-covered areas, clouds normally have a similarly high reflectance, reflecting most of the sun’s energy back out to space. But as the ocean becomes ice-free, the high albedo of clouds can counteract the ocean warming expected from increased solar absorption. Their study, based on climate model experiments, argues that with low levels of carbon dioxide (e.g. pre-industrial), sea ice covers the ocean through most of the summer, and clouds have little influence on sea surface temperatures. However, as carbon dioxide levels rise and the sea ice retreats, the countering cooling effect of clouds grows. Looking to the future, their findings suggest that when the Arctic becomes seasonally ice free, the maximum sea surface temperature becomes three times more sensitive to clouds than in the pre-industrial era. This argues that the representation of clouds and their radiative impacts is important for accurately modeling heat input to the upper ocean as the Arctic transitions to being seasonally ice free.

Antarctic extent remains low

Figure 4. Antarctic sea ice extent for April 2023 was 5.50 million square kilometers (2.12 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

While ice extent in the Antarctic is increasing in response to the changing of the seasons, extent remained well below average through April, particularly in the Bellingshausen Sea, where the ocean is nearly ice free along the entire coast, and the eastern Weddell Sea (Figure 4). Sea ice extent quickly returned to near average in the Amundsen and Ross Seas and most of the East Antarctic coast after the record low set in February of this year. At the end of the month, daily extent was the second lowest in the satellite record.

A recent study discussed the earlier 2022 record low Antarctic sea ice extent as a consequence, in part, of an unusually strong and eastward-shifted Amundsen Sea Low (ASL) during the austral spring of 2021. While this study emphasized ice export caused by the western arm of the ASL, we note that its eastern side is responsible for bringing northerly winds into the Bellingshausen Sea and strong surface melting and ice advection away from the Antarctic Peninsula coast. This pattern occurred again in the austral spring of 2022 with an almost identical position and strength of the ASL, leading to a new record low ice extent in February 2023 as we reported in March.

References

Sledd, A., R. S. L’Ecuyer, J. E. Kay, and M. Steele. 2023. Clouds increasingly influence Arctic sea surface temperatures as CO₂ rises. Geophysical Research Letters. doi:10.1029/2023GL102850.

Wang, S., J. Liu, X. Cheng, D. Yang, T. Kerzenmacher, X. Li, Y. Hu, and P. Braesicke. 2023. Contribution of the deepened Amundsen Sea Low to the record low Antarctic sea ice extent in February 2022. Environmental Research Letters. doi:10.1088/1748-9326/acc9d6.

Sunlight has returned to the highest latitudes in the Arctic, while in the Antarctic autumn is settling in. The seasonal decline of Arctic sea ice extent since the March 6 annual maximum has been slow, but daily extent has remained among the third to sixth lowest in the satellite record. Since the seasonal minimum reached on February 21, Antarctic sea ice has expanded at a fairly typical pace.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2023 was 14.44 million square kilometers (5.58 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of April 4, 2023, along with daily ice extent data for four previous years and the record low year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 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. Sea Ice Index data.

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

The March 2023 average Arctic sea ice extent was 14.44 million square kilometers (5.58 million square miles), the sixth lowest March in the satellite record (Figure 1a). March monthly average extent was 990,000 square kilometers (382,000 square miles) below the 1981 to 2010 average of 15.43 million square kilometers (5.96 million square miles), but 150,000 square kilometers (57,900 square miles) above the record low set in March 2017 (Figure 1b).

After the March 6 seasonal maximum, extent declined for a week, but then remained almost constant during the second half of the month. Ice extent was slightly below average in almost all areas, but particularly in the Sea of Okhotsk and in the Gulf of St. Lawrence, with smaller retreats in the Barents and Bering Seas. Sea ice concentration within the ice pack was generally quite high in all areas, with the exception of the Sea of Okhotsk and the northern Barents Sea where the ice pack was more open.

Overall, extent decreased 170,000 square kilometers (65,600 square miles) during March 2023, compared to the 1981 to 2010 average March decrease of 220,000 square kilometers (84,900 square miles).

Conditions in context

Figure 2a. This plot shows average sea level pressure in the Arctic in millibars for March 2023. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

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

Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for March 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

March weather conditions were dominated by persistent high sea level pressure over northern Canada and Greenland, and low sea level pressure over northern Europe and European Russia (Figure 2a). This led to winds from the south and warm conditions over Baffin Bay and western Greenland with temperatures up to 6 to 7 degrees Celsius above average (11 to 13 degrees Fahrenheit) (Figure 2b). Cool conditions extended from Iceland to Franz Josef Land, where temperatures were 4 to 6 degrees Celsius below average (7 to 11 degrees Fahrenheit).

March 2023 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2023 shows a decline of 2.5 percent per decade.

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

The downward linear trend for Arctic sea ice extent in March over the 45-year satellite record is 38,900 square kilometers (15,000 square miles) per year, or 2.5 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, March has lost 2.28 million square kilometers (880,000 square miles). This is roughly eight and a half times the size of Colorado or six and a half times the size of Germany.

Arctic sea ice age

Figure 4. The top maps show sea ice age for the week of February 26 to March 4 for (a) 1985  and (b) 2023. The bottom graph is a timeseries of the percent of the sea ice extent within the Arctic Ocean domain (inset map) for the week of February 26 to March 4, 1985, through 2023; color categories are the same as in the maps. Data and images from NSIDC EASE-Grid Sea Ice Age, Version 4 (Tschudi et al., 2019a) and Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1 

Credit: Tschudi et al., 2019b
High-resolution image

An important indicator of sea ice conditions is the sea ice age. As in recent years, there is far less multiyear ice (ice that has survived at least one summer melt season) and the oldest ice (ice that has survived several or more melt seasons) is nearly gone. Multiyear ice covered 33.9 percent of the Arctic Ocean domain in the week of February 26 through March 4, 2023, slightly less than the 34.3 percent during the same week in 2022. This is much less than in the late 1980s when multiyear ice covered 60 to 65 percent of the Arctic Ocean.

A rapid decline in multiyear ice coverage occurred after the then record 2007 September sea ice extent minimum. The multiyear ice coverage has been variable since then, with no significant trend. Overall, there is almost no ice over four years old remaining—it now comprises just 3 percent of the total ice cover. This is the same percentage as last year and contrasts starkly with the late 1980s when 30 to 35 percent of the Arctic Ocean’s ice was older than 4 years. Since 2011, the older-than-four-year-old ice has comprised less than 5.5 percent of the Arctic Ocean. These results are consistent with a new study that evaluated the thickness of ice from moorings in Fram Strait, finding a shift in the ice thickness after 2007 and a decline of the average residence time of ice in the Arctic Ocean.

Autumn in the Antarctic

Figure 5. Antarctic sea ice extent for March 2023 was 2.80 million square kilometers (1.08 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Antarctic sea ice extent expanded at a near-average pace in March following its record low extent on February 21. At the end of the month, the Ross Sea and Amundsen Sea were covered again with ice, and significant expansion of ice had begun in the Weddell Sea. However, large areas of the coast, such as the southern Bellingshausen Sea coastline were still ice free; other areas of open water persisted along the boundary between the Amundsen and Ross Seas. Despite regrowth, the Weddell Sea ice cover is well below its typical extent for the end of March.

The March 2023 average sea ice extent around Antarctica was 2.80 million square kilometers (1.08 million square miles), the second lowest March on record. This is 100,000 square kilometers (38,600 square miles) more than the record low extent for March set in 2017.

Ocean circulation changes in the Southern Ocean

Figure 6a. This map shows global ocean circulation, including the major areas of ocean water sinking and upwelling. This is often called the global ocean conveyor belt.

Credit: Modified from National Geographic
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Figure 6b. This schematic diagram of the Southern Ocean portion of the global ocean circulation shows the changes in the recent decades, on the right, relative to the earlier pattern, on the left.

Credit: Lee et al., 2023
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The ocean circulation, which includes well-known surface and subsurface currents and the vertical motion of ocean water, appears to have changed in a major way over the Southern Hemisphere in recent decades. Increased contributions of meltwater from the Antarctic Ice Sheet, mostly from melting at depth due to increased warm deep water reaching the edge of the continent, has added freshwater to the sea currents, making the water less dense. This lighter water flows up to the surface, increasing the stratification in the near-surface layer. Because the stratification is stronger, the vertical ocean circulation has slowed.

These changes reflect changing winds around the continent, resulting from both the ozone hole, which cools the Antarctic stratosphere, increasing the westerly circumpolar winds, and increased carbon dioxide and methane in the air, which warms the tropics, again making the far southern winds stronger.

Great Scott! The Great Lakes in 2023

Figure 7a. This map of the Great Lakes shows ice cover on February 4th, 2023, the date of maximum ice cover for 2023. 

Credit: US National Ice Center
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Figure 7b. This plot shows the departure from average air temperature in the Great Lakes Region at the 925 hPa level, in degrees Celsius, from December 1, 2022, to March 29, 2023, relative to the 1991 to 2020 average. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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This year, the maximum ice cover area of the Great Lakes, as monitored by the US National Ice Center in Suitland Maryland, was 23.35 percent on February 4, 2023, and for much of the winter ice cover was below 10 percent (Figure 7a). Winter temperatures over the Great Lakes ranged from 0.5 degrees Celsius (1 degree Fahrenheit) above the 1991 to 2020 average over Lake Superior to more than 2 degrees Celsius (4 degrees Fahrenheit) above average over Lake Ontario (Figure 7b).

Although the year-to-year variability in Great Lakes ice cover is high, an analysis led by Jia Wang, an ice climatologist at the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL), found that average winter ice cover on the Great Lakes has declined 69 percent between1973 and 2017, with the greatest losses in Lake Superior and Lake Ontario. However, nearly complete ice cover was seen as recently as 2019. Historically, widespread ice cover over Lake Michigan and Lake Erie (and many other areas) supported ice harvesting for refrigeration.

In memoriam: Josh King

Figure 8. This photograph is a portrait of Josh King.

Credit: Steve Howell, Environment and Climate Change Canada
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It is with great sadness that another colleague of ours recently passed away. Josh King was a dedicated snow field scientist who collected invaluable snow observations throughout the Arctic region during his career. In 2017, NSIDC scientist Julienne Stroeve and others worked with King to collect snow and ice data in the Lincoln Sea, the region of the Arctic known as the Last Ice Area. Stroeve remembers how professional King was in leading the data collection efforts, keeping the team motivated while working tirelessly after returning back to base each night to keep instruments operational and quality control the data collected. It is a great loss for the scientific community to lose a colleague at such a young age.

References

Holling, H. C. 1941. Paddle-to-the-Sea. Boston, Houghton Mifflin

Ice Harvesting in Sandusky

Lee, S. K., R. Lumpkin, F. Gomez, S. Yeager, H. Lopez, F. Takglis, S. Dong, W. Aguiar, D. Kim, and M. Baringer. 2023. Human-induced changes in the global meridional overturning circulation are emerging from the Southern Ocean. Nature Communications Earth and Environment 4, 69, doi:10.1038/s43247-023-00727-3.

National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL) Annual Max Ice Cover Animation

Sumata, H., de Steur, L., Divine, D.V. et al. 2023. Regime shift in Arctic Ocean sea ice thickness. Nature 615, 443–449, doi:10.1038/s41586-022-05686-x.

Tschudi, M., W. N. Meier, J. S. Stewart, C. Fowler, and J. Maslanik. 2019a. EASE-Grid Sea Ice Age, Version 4 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/UTAV7490FEPB. Date Accessed 03-31-2023.

Tschudi, M., W. N. Meier, and J. S. Stewart. 2019. Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/2XXGZY3DUGNQ. Date Accessed 03-31-2023.

Wang, J., J. Kessler, F. Hang, H. Hu, A. Clites, and P. Chu. 2017. Great Lakes ice climatology update of winters 2012-2017: Seasonal cycle, interannual variability, decadal variability, and trend for the period 1973-2017. NOAA Technical Memorandum GLERL-170.

Arctic sea ice has likely reached its maximum extent for the year, at 14.62 million square kilometers (5.64 million square miles) on March 6. The 2023 maximum is the fifth lowest in the 45-year satellite record. NSIDC scientists will present a detailed analysis of the 2022 to 2023 winter sea ice conditions in the regular monthly post in early April.

Overview of conditions

Figure 1. This image shows Arctic sea ice extent on March 7, 2023, which was 14.62 million square kilometers (5.64 million square miles) like the extent on March 6, 2023. The March 7 image is being used because of missing data on the prior day’s map. The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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On March 6, 2023, Arctic sea ice likely reached its maximum extent for the year, at 14.62 million square kilometers (5.64 million square miles), the fifth lowest extent in the satellite record. This year’s maximum extent is 1.03 million square kilometers (398,000 square miles) below the 1981 to 2010 average maximum of 15.65 million square kilometers (6.04 million square miles) and 210,000 square kilometers (81,000 square miles) above the lowest maximum of 14.41 million square kilometers (5.56 million square miles) set on March 7, 2017.

The date of the maximum this year, March 6, was six days earlier than the 1981 to 2010 average date of March 12.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 6, 2023, along with daily ice extent data for four previous years and the record low year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 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. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The ice growth season ended with below average sea ice extent in the Bering Sea, Sea of Okhotsk, Barents Sea, and Labrador Sea. Above average extent was in the Greenland Sea. Extent was well below average in the Gulf of St. Lawrence for a second year in row.

Since the maximum on March 6, extent has dropped about 200,000 square kilometers (77,000 square miles), with losses primarily in Labrador Sea, Gulf of St. Lawrence, and the Barents Sea.

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

For the Arctic maximum, which typically occurs in March, the uncertainty range is ~34,000 square kilometers (13,000 square miles), meaning that extents within this range must be considered effectively equal.

Throughout February, Arctic sea ice extent tracked between second and fourth lowest in the satellite record while Antarctic sea ice extent tracked at record low extents. Antarctic sea ice has hit its minimum extent for the year, setting a new record low, and is now expanding.

Overview of conditions

Figure 1a. Arctic sea ice extent for February 2023 was 14.18 million square kilometers (5.47 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 1b. The graph above shows Arctic sea ice extent as of March 1, 2023, along with daily ice extent data for four previous years and the record high year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 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. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The February 2023 average Arctic sea ice extent was 14.18 million square kilometers (5.47 million square miles), the third lowest February in the satellite record (Figure 1a). February extent was 1.12 million square kilometers (432,000 square miles) below the 1981 to 2010 average of 15.30 million square kilometers (5.91 million square miles), but 210,000 square kilometers (81,000 square miles) above the record low set in February 2018.

The overall daily rate of increase in extent through the month was near average, but with periods of rapid increase at the start and the middle of the month, followed by periods of little change (Figure 1b). This is not uncommon for this time of year as ice growth slows and the ice edge is vulnerable to winds that either compress or expand the ice cover. Ice expansion slowed the last week of February and while the seasonal maximum does not appear to have been reached, it is likely not far away. The seasonal maximum has occurred as early as February 24 in 1987 and 1996 and as late as April 2 in 2010.

Overall, extent increased 724,000 square kilometers (280,000 square miles) during February 2023, compared to the 1981 to 2010 average February increase of 573,000 square kilometers (221,000 square miles). Regionally, extent remained below average in the Barents Sea, the Sea of Okhotsk, and the Gulf of St. Lawrence. In the Bering Sea, the ice extent was closer to average.

Conditions in context

Figure 2a. This plot shows average sea level pressure in the Arctic in millibars for February 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for February 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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During February, the Arctic Oscillation, a large-scale mode of Arctic climate variability, was in a strongly positive phase. When the Arctic Oscillation index is positive, the low sea level pressure over Svalbard strengthens, and the winds circulating around the North Pole are stronger, helping to keep cold air in the Arctic Ocean. The sea level pressure pattern for February featured unusually low sea level pressure over Svalbard coupled with high pressure over the central Arctic Ocean and Siberia (Figure 2a). The Siberian High and Beaufort Sea High are common features of winter, yet this February, the Beaufort Sea High shifted more towards the Pole. The combination of low pressure over Svalbard and high pressure over the central Arctic Ocean helped drive relatively warm air from the south across the North Atlantic and into the Barents Sea, and push cold Arctic air towards the Bering Sea. Cold Arctic air was also drawn westwards into eastern Canada. Air temperatures of up to 6 degrees Celsius (11 degrees Fahrenheit) below average  were also found over Baffin Bay and Hudson Bay (Figure 2b).

Another noteworthy atmospheric event of February was a sudden stratospheric warming (SSW). These occur when atmospheric longwaves propagate into the stratosphere, weakening or even reversing the stratospheric polar vortex. The effects can then propagate downward into the troposphere, enabling cold Arctic air to spill into lower latitudes. Heading into February, it appears that the stratospheric vortex was already in a weakened state because of vertical wave propagation. This made it susceptible to further breakdown about 10 days later when the vortex center shifted from the pole toward Europe. Overall, SSW events generally lead to Arctic sea ice growth, though the exact response varies by region.

February 2023 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2023 shows a decline of 2.8 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in February sea ice extent over the 45-year satellite record is 42,300 square kilometers (16,300 square miles) per year, or 2.8 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, February extent has lost 1.86 million square kilometers (718,000 square miles) of ice. This is equivalent to about seven times the size of Colorado or about five times the size of Germany.

The role of atmospheric rivers in keeping Arctic winter sea ice extent low

Figure 4. This figure shows November to January averaged trends in atmospheric river (AR) events. The Arctic map (a) shows AR frequency trend from the ERA5 model and two other climate re-analyses. The plot (b) shows a time series of ARs in the Barents and Kara Seas from three different atmospheric reanalysis data sets together with the sea ice area in that region. AR frequency refers to the number of atmospheric river events in the late-fall/early-winter period; ABK (Arctic-Barents-Kara) refers to the area outlined in red in the map, and SIA is sea ice area.

Credit: Zhang et al., 2023
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In recent years, low sea ice extent in the Barents and Kara Seas has driven the overall negative trend in winter Arctic sea ice. Previous studies attributed the low ice cover in this region to increased ocean heat transport from the North Atlantic. A new study is looking at the role of atmospheric rivers as a contributing process. Atmospheric rivers bring in warm moist air from the tropics and subtropics, increasing the downward longwave radiation to the surface. They can also bring heavy rainfall. Both processes can melt sea ice. According to the study, more atmospheric rivers are entering the Eurasian Arctic than previously, leading to reduced ice formation or melting of thin ice in November through January.

The Kivalliq polynya

Figure 5. This NASA Visible Infrared Imaging Radiometer Suite (VIIRS) visible image was taken on February 6, 2023. The darker area on the western half of the Bay is newly formed sea ice where the polynya opened.

Credit: The National Oceanic and Atmospheric Administration Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin-Madison Satellite Blog
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Hudson Bay is generally completely ice covered during the Arctic winter. However, as in other places, polynyas, regions of persistent open water, can occur under certain conditions. In western Hudson Bay, openings and closings of what is called the Kivalliq polynya are regular events related to strong winds. This polynya forms in winter as offshore winds push the ice away from the coast. As ice is pushed away, the open water left behind begins to freeze and new ice quickly forms. On average, about 182 cubic kilometers (43.7 cubic miles) of new ice is produced annually in this polynya, equivalent to about 20 percent of the winter ice volume of Hudson Bay, according to colleagues at the University of Manitoba. On January 21, the Kivalliq polynya once again opened and was soon covered by thin ice that was observed in visible and thermal satellite imagery. Synthetic Aperture Radar (SAR) and L-band passive microwave data from the Soil Moisture and Ocean Salinity (SMOS) satellite also captured the opening and closing of the polynya. Interestingly, the ice reflectance and the surface temperature in this region two weeks later was quite uniform, suggesting very uniform ice thickness (Figure 5). Polynyas such as this one not only facilitate ice production, they are also biologically important regions, fostering springtime phytoplankton blooms. They also play a large role in heat and moisture exchanges between the ocean and the colder atmosphere above it. Moreover, they lead to the production of dense, cold, and salty water as the sea ice freezes. Sea ice crystals are fresh ice and the formation of the crystals reject the salt brine, leading to dense descending water.

Antarctic sea ice may be reversing course

Figure 6a. Antarctic sea ice extent for February 2023 was 1.90 million square kilometers (734,000 square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 6b. Antarctic sea ice concentration for February 2023 was 1.20 million square kilometers (463,000 square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Antarctic sea ice extent continued to track at record lows for this time of year. By the end of February, extent was 1.83 million square kilometers (707,000 square miles). This is 93,000 square kilometers (35,900 square miles) below the record seasonal minimum that occurred on February 25, 2022. Extent remained particularly low in the Amundsen, Bellingshausen, and Ross Seas (Figure 6a). Most of the sea is ice gone from the Ross Sea, and what little ice remains in the Amundsen/Bellingshausen Seas is very low concentration (Figure 6b). In the Weddell Sea, the ice edge remains near average for this time of year.

Until recently, there was a weak overall upward trend in Antarctic sea ice extent, but with some parts of the Antarctic sea ice exhibiting strong positive trends in extent and other areas exhibiting strong negative trends. According to colleagues at Commonwealth Scientific and Industrial Research Organisation (CSIRO Australia), this pattern is changing. Over the past decade, there is less regional variability. Patterns of sea ice extent variations, high or low, have become more uniform around the continent. This has contributed to the lower Antarctic sea ice extents that have been observed since 2016.

References

Bruneau, J., D. Babb, W. Chan, S. Kirillov, J. Ehn, J. Hanesiak, and D. G. Barber. 2021. The ice factory of Hudson Bay: Spatiotemporal variability of the Kivalliq Polynya. Elementa: Science of the Anthropocene, 9, (1). doi:10.1525/elementa.2020.00168.

Schroeter, S., T. J. O’Kane, and P. A. Sandery. 2023. Antarctic sea ice regime shift associated with decreasing zonal symmetry in the Southern Annular Mode. The Cryosphere, 17, 701–717, doi:10.5194/tc-17-701-2023.

Smith, K. L., L. M. Polvani, and L. B. Tremblay, L. B. 2018. The Impact of Stratospheric Circulation Extremes on Minimum Arctic Sea Ice Extent. Journal of Climate, 31(18), 7169-7183. doi:10.1175/JCLI-D-17-0495.1.

Zhang, P., G. Chen, M. Ting, et al. 2023. More frequent atmospheric rivers slow the seasonal recovery of Arctic sea ice. Nature Climate Change. doi:10.1038/s41558-023-01599-3.

On February 21, Antarctic sea ice likely reached its annual minimum extent of 1.79 million square kilometers (691,000 square miles). This the lowest sea ice extent in the 1979 to 2023 sea ice record, setting a record low for the second straight year.

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Antarctic ice extent. NSIDC scientists will release a full analysis of the Antarctic and Arctic February conditions in early March.

Overview of conditions

Figure 1. Antarctic sea ice extent for February 21, 2023, was 1.79 million square kilometers (691,000 square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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On February 21, 2023, sea ice in the Antarctic reached an annual minimum extent of 1.79 million square kilometers (691,000 square miles), setting a record low in the satellite record that began in 1979. This year’s minimum is 1.05 million square kilometers (405,000 square miles) below the 1981 to 2010 average Antarctic minimum extent. It is 136,000 square kilometers (52,500 square miles) below the previous record low from February 25, 2022. Nearly all of the remaining ice is in the Weddell Sea, with isolated patches along the coasts of Princess Astrid and Princess Ragnild and regions of eastern Wilkes Land and the Pine Island Bay.

The Antarctic minimum extent was reached three days earlier than the 1981 to 2010 median date of February 24. The interquartile range for the date of the Antarctic minimum is February 20 to February 27.

Conditions in context

Figure 2a. The graph above shows Antarctic sea ice extent as of February 21, 2023, along with daily ice extent data for four previous years and the record high year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 in magenta, and 2013 to 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. This graph shows Antarctic annual sea ice minimum extent, depicted as black diamonds, from 1979 to 2023, based on a 5-day running average of daily extent. The linear trend line is in blue with a 1.0 percent per decade downward trend, which is not statistically significant. A five-year running average is shown in red.

Credit: W. Meier, NSIDC
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This year marks a second consecutive record low in Antarctic sea ice extent (Figure 2a). In recent years, 2017 and 2018 also reached very low extents, third and fourth lowest, respectively. With this series of low years, it is natural to speculate if there is now a downward trend. However, a trend computed over such a short time period is not especially meaningful. Note in this respect that 2013 through 2015 saw near record high minimum extents.

Overall, the downward trend in the annual Antarctic sea ice minimum extent computed over the complete satellite record is 2,800 square kilometers (1,100 square miles) per year, or 1.0 percent per decade relative to the 1981 to 2010 average. This trend is not statistically significant (Figure 2b). This is in stark contrast to the Arctic where the trend in the sea ice minimum is larger in magnitude and has strong statistical significance.

Antarctic sea ice extent appears to have broken the record low set last year. With a couple more weeks likely left in the melt season, the extent is expected to drop further before reaching its annual minimum. Much of the Antarctic coast is ice free, exposing the ice shelves that fringe the ice sheet to wave action and warmer conditions.

Overview of conditions

Figure 1a. This map of Antarctica shows many low areas of sea ice concentration, depicted as darker blues, surrounding the continent, rendering extent likely to decrease in the coming days or weeks. Antarctic sea ice extent for February 13, 2023, was 1.91 million square kilometers (737,000 square miles). The orange line shows the 1981 to 2010 median extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 1b. The graph above shows Antarctic sea ice extent as of February 13, 2023, along with daily ice extent data for four previous years and the record high year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 in magenta, and 2013 to 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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On February 13, 2023, Antarctic sea ice extent fell to 1.91 million square kilometers (737,000 square miles) (Figure 1a). This set a new record low, dropping below the previous record of 1.92 million square kilometers (741,000 square miles) set on February 25, 2022 (Figure 1b). This year represents only the second year that Antarctic extent has fallen below 2 million square kilometers (772,000 square miles). In past years, the annual minimum has occurred between February 18 and March 3, so further decline is expected.

Conditions in context

Figure 2. This graph shows Antarctic annual sea ice minimum extent, depicted as black diamonds, from 1979 to 2023, based on a 5-day running average of daily extent. The grey diamond data point depicts the 2023 minimum, which is still preliminary, with further loss expected. The linear trend line is in blue with a 0.9 percent per decade downward trend, which is not statistically significant. A five-year running average is shown in red. As the Antarctic melt season is still in progress, depicted as a grey downward arrow, the linear trend and running average will change slightly.

Credit: W. Meier, NSIDC
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Extent has tracked well below last year’s melt season levels since mid-December. As noted in our previous post, a positive Southern Annular Mode has led to stronger-than-average westerly winds. Along with a strong Amundsen Sea Low, the weather conditions have brought warm air to the region on both sides of the Antarctic Peninsula. This has largely cleared out the ice cover in the Amundsen and Bellingshausen Seas, and reduced the sea ice extent in the northwestern Weddell Sea. Sea ice is patchy and nearly absent over a long stretch of the Pacific-facing coastline of Antarctica.  Earlier studies have linked low sea ice cover with wave-induced stresses on the floating ice shelves that hem the continent, leading to break up of weaker areas.

Antarctic sea ice extent has been highly variable over the last several years. While 2022 and 2023 have had record low minimum extent, four out of the five highest minimums have occurred since 2008. Overall, the trend in Antarctic minimum extent over 1979 to 2023 is near zero. The current downward linear trend in the Antarctic minimum extent from 1979 to 2023 is 2,400 square kilometers (930 square miles) per year, or 0.9 percent per decade, which is currently not statistically significant. Nevertheless, the sharp decline in sea ice extent since 2016 has fueled research on potential causes and whether sea ice loss in the Southern Hemisphere is developing a significant downward trend.

Arctic sea ice extent rose at a slower than average rate through January, and continued to be below the lower interdecile range. By the end of the month, sea ice reached the second lowest extent in the satellite record. Meanwhile, Antarctic extent remained at record low levels. Combined, the two hemispheres set a record low for total global sea ice extent, yet this does not signify a trend necessarily and may be caused by weather-related variability.

Overview of conditions

Figure 1a. Arctic sea ice extent for January 2023 was 13.35 million square kilometers (5.15 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 1b. The graph above shows Arctic sea ice extent as of February 5, 2023, along with daily ice extent data for four previous years and the record low year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The January 2023 average Arctic sea ice extent was 13.35 million square kilometers (5.15 million square miles), the third lowest January in the satellite record (Figure 1a). January extent was 1.07 million square kilometers (413,000 square miles) below the 1981 to 2010 average of 14.42 million square kilometers (5.57 million square miles), but 270,000 square kilometers (104,000 square miles) above the record low set in January 2018.

The daily rate of increase in extent was near average through the first half of the month, but slowed during the second half, and extent slightly declined near the end of the month (Figure 1b). Such short-term declines are not unusual in winter and typically reflect responses to weather patterns. Nevertheless, by the end of the month, the overall daily extent tracked at second lowest in the satellite data record. Overall, extent increased 1.09 million square kilometers (421,000 square miles) during January 2023, compared to the 1981 to 2010 average January increase of 1.33 million square kilometers (514,000 square miles).

Regionally, extent remained particularly low in the Barents Sea, and below average extent was also found in the Sea of Okhotsk, the Bering Sea, and the Gulf of St. Lawrence.

Conditions in context

Figure 2a. This plot shows average sea level pressure in the Arctic in millibars for January 2023. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Figure 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for January 2023. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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The sea level pressure pattern for January featured high pressure over the Pacific sector of the Arctic Ocean (Figure 2a). This feature is known as the Beaufort High and is common in winter and spring. The location of the high varies, but on average it is centered over the Beaufort Sea and drives the Beaufort Gyre, which brings ice from north of Greenland and the Canadian Arctic Archipelago through the Beaufort and into the Chukchi Sea. By contrast, over on the Atlantic side of the Arctic, low pressure dominated in the Barents Sea region. As a result, relatively warm air from the south moved into the Barents Sea region, leading to air temperatures at the 925 millibar level (approximately 2,500 feet above the surface) more than 6 degrees Celsius (11 degrees Fahrenheit) above average near Svalbard (Figure 2b). The lack of sea ice in the Barents Sea likely also contributed to above average air temperatures. Elsewhere, air temperatures were above average over most of the Arctic Ocean, with departures from average ranging from 1 degree Celsius (2 degrees Fahrenheit) to 5 degrees Celsius (9 degrees Fahrenheit).

January 2023 compared to previous years

Figure 3. Monthly January ice extent for 1979 to 2023 shows a decline of 3.0 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in January sea ice extent over the 44-year satellite record is 42,500 square kilometers (16,400 square miles) per year, or 3.0 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979, January has lost 1.89 million square kilometers (730,000 square miles). This is equivalent to about seven times the size of Colorado or about twice the size of Germany.

Antarctic sea ice at record lows for January

Figure 4a. Antarctic sea ice extent for January 2023 was 3.23 million square kilometers (1.25 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 4b. This maps shows Antarctic sea ice concentration for January 2023. The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Antarctic sea ice extent maintained record lows for this time of year. On February 1, 2023, the extent was 2.26 million square kilometers (873,000 square miles). This is 270,000 square kilometers (104,000 square miles) below the previous February 1 record low in 2017, and  310,000 square kilometers (120,000 square miles) above the record seasonal minimum in extent that occurred on February 25, 2022. Regionally, extent was particularly low in the Amundsen, Bellingshausen, and Ross Seas (Figure 4a). Typically, sea ice is still present along most of the coastline from the eastern Ross Sea to the Antarctic Peninsula, but this year, most of that coast is largely ice free. Extent is also below average along the Wilkes Land coast in East Antarctica, but near average elsewhere around the continent. Large areas of low concentration sea ice are in the Weddell, Ross, and Amundsen Sea ices (Figure 4b). These areas are likely to melt out before the minimum for 2023 is reached, which is expected to occur late this month or in early March.

Weather conditions around Antarctica have been characterized by stronger-than-average westerly winds (a positive Southern Annular Mode index) and a strong and eastward-positioned Amundsen Sea Low. Air temperatures at the 925 millibar level (about 2,500 feet above sea level) have been 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above average since November in a broad area of the coast stretching clockwise from the eastern Wilkes Land through the Ross and Amundsen Sea, and over most of the Weddell Sea. However, warm ocean waters just below the surface layer are also thought to be playing a role in the general downward trend of Antarctic sea ice since 2016 (Zhang et al., 2022).

The January 2023 average Antarctic extent of 3.23 million square kilometers (1.25 million square miles) is the lowest January extent in the satellite record, below the previous January record low of 3.78 million square kilometers (1.46 million square miles) set in 2017. The downward linear trend in January sea ice extent is 6,400 square kilometers (2,500 square kilometers) per year or 1.3 percent per decade relative to the 1981 to 2010 average.

Arctic freeze/thaw from above and below

A key component in the seasonal and interannual evolution of Arctic sea ice is the timing of melt onset and freeze up. Surface melt and freeze up can be obtained from satellite passive microwave observations but satellite observations do not provide information about what is happening under the ice. The length of the melt season is much longer underneath sea ice as a result of ocean heat. A recent study evaluated data collected from sea ice mass balance buoys (IMBs) and upward looking sonar (ULS) instruments to gain insights on the seasonality of ice melt and freeze up below the ice. Over the period from 2001 to 2018, Lin and colleagues found that in the Beaufort Sea, the bottom melt onset began 17 days before the surface melt. By contrast, in the central Arctic the timing of the melt onset of the top and bottom of the ice was similar. The freeze up of the bottom of the ice began about three weeks after the surface started to freeze. The researchers also found that bottom melt onset occurred about a week earlier during the 2010 to 2018 period compared to the 2001 to 2009 period, because of rising ocean temperatures. Bottom freeze up began one to two weeks earlier in the later period compared to the earlier period because thinner ice allowed faster heat loss from the ocean.

References

Arctic Sea Ice Melt Data Set

Bliss, A. C., M. Anderson, and S. Drobot. 2022. Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures, Version 5 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi:10.5067/TRGWQ0ONTQG5.

Lin, L., R. Lei, M. Hoppmann, D. K. Perovich, and H. 2022. Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018. The Cryosphere, 16, 4779–4796, doi:10.5194/tc-16-4779-2022.

Steele, M., A. C. Bliss, G. Peng, W. N. Meier, and S. Dickinson. 2019. Arctic Sea Ice Seasonal Change and Melt/Freeze Climate Indicators from Satellite Data, Version 1 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi:10.5067/KINANQKEZI4T.

Zhang, L., T. L. Delworth, X. Yang, et al. 2022. The relative role of the subsurface Southern Ocean in driving negative Antarctic Sea ice extent anomalies in 2016–2021. Communications Earth and Environment 3, 302. doi:10.1038/s43247-022-00624-1.

Daily extent of Arctic sea ice for December 2022 remained well below average for the entire month; at the end of the month, extent stood at fourth lowest in the satellite record. The average extent for the month ended up as seventh lowest in the satellite record. Antarctic extent is declining much faster than average as austral summer takes hold and is setting record low daily ice extents for the satellite era as of December 22. As such, global sea ice extent is well below average.

Overview of conditions

Figure 1a. Arctic sea ice extent for December 2022 was 11.92 million square kilometers (4.60 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
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Figure 1b. The graph above shows Arctic sea ice extent as of January 4, 2023, along with daily ice extent data for four previous years and the record low year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The average Arctic sea ice extent for December 2022 was 11.92 million square kilometers (4.60 million square miles). This is the seventh lowest in the satellite record for the month (Figure 1a). Extent was 920,000 square kilometers (355,000 square miles) below the 1981 to 2010 average of 12.84 million square kilometers (4.96 million square miles) and 460,000 million square kilometers (178,000 square miles) above the record December low set in 2016 of 11.46 million square kilometers (4.42 square miles).

The rate of ice growth through the month was variable. It was faster than average through the first half of the month, then growth slowed, and then picked up the pace again. Over the last week of the month, ice growth was very slow, and as a result, total extent at the end of December stood at fourth lowest in the satellite record (Figure 1b). Regionally, at month’s end, the ice edge was notably north of its average location in the Barents Sea and on the Russian side of the Bering Sea. Hudson Bay is now almost completely iced over.

Conditions in context

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

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

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Average December air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) were above the 1991 to 2020 average over essentially all of the Arctic Ocean, but notably in the area centered over the East Siberian Sea (Figure 2a). The unusually warm conditions in this area, which were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) above average, appear to be related to the large area of below-average sea level pressure over the northern North Pacific Ocean pumping warm air into the East Siberian Sea (Figure 2b). Air temperatures were also above average over the eastern Canadian Arctic and most of Greenland.

December 2022 compared to previous years

Figure 3. Monthly December ice extent for 1978 to 2022 shows a decline of 3.5 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in December sea ice extent over the 45-year satellite record is 44,400 square kilometers (17,100 square miles) per year, or 3.5 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1978, November has lost 2.28 million square kilometers (880,000 square miles). This is equivalent to about 1.5 times the size of Alaska.

The year in review

Figure 4a. The graph above shows Arctic sea ice extent for 2022 (blue line) and 2012, the record minimum year (dashed red line). The gray line shows the 1981 to 2010 median, the dark gray shaded area shows the interquartile range, and the light gray shaded area shows the interdecile range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 4b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for summer 2022 from June 1 to August 31. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Figure 4c. This plot shows average sea level pressure in the Arctic in millibars for summer 2022 from June 1 to August 31. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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While Arctic sea ice extent was below average over the entire year (Figure 4a), no records were set, and the September average sea ice extent, at 4.87 million square kilometers (1.88 million square miles), tied with 2010 as only the eleventh lowest in the satellite record. The September daily minimum extent, set on September 18 at 4.67 million square kilometers (1.80 million square miles), tied with 2017 and 2018 for tenth lowest in the satellite record. The September minimum extent is strongly dependent on summer weather conditions, and summer average air temperatures, while above climatological averages over most of the Arctic Ocean, were not extreme (Figure 4b), generally from 1.5 to 2.5 degrees Celsius (3 to 4.5 degrees Fahrenheit) above the 1991 to 2020 baseline. The summer average sea level pressure pattern was in turn quite flat, meaning light winds. A pronounced Beaufort Sea High, which generally favors low September sea ice extent, is notably lacking (Figure 4c).

Ice down under

Figure 5a. This map from January 3, 2023, shows a large polynya that now spans the Ross Sea and much of the western Amundsen Sea, as well as polynyas that have appeared in Pine Island Bay and the southeastern Weddell Sea. Sea ice concentration data are from the Japan Aerospace Exploration Agency Advanced Microwave Scanning Radiometer 2 (AMSR2) imagery.

Credit: University of Bremen
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Figure 5b. This plot shows the departure from average air temperature in the Antarctic at the 925 hPa level, in degrees Celsius, for November and December 2022. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Laboratory
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Summer is taking hold in the Southern Hemisphere. While the decline in Antarctic Sea ice extent is always steep at this time of year, it has been unusually rapid this year, and at the end of December, Antarctic sea ice extent stood at the lowest in the 45-year satellite record. Sea ice extent was more than 500,000 square kilometers (193,000 square miles) below the previous record year of 2018; four of the five lowest years for the last half of December have occurred since 2016. As is evident in sea ice maps prepared by colleagues at the University of Bremen from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2) data, an extremely large polynya now spans the Ross Sea and much of the western Amundsen Sea. Polynyas have also appeared in Pine Island Bay and the southeastern Weddell Sea (Figure 5a). There are also extensive areas of low sea ice concentration in the Weddell Sea that are likely ready to melt out.

Weather-related causes for the unusually low sea ice extent seem to stem from a band of above-average  temperatures extending from the Weddell Sea westward to the Ross Sea and eastern Wilkes Land (Figure 5b). Air temperatures at the 925 mb level were more than 1 degree Celsius (2 degrees Fahrenheit) above average over the entire area in November and December, and were more than 2 degrees Celsius (4 degrees Fahrenheit) above average over the Ross Sea. The past two months have seen periods of strong circumpolar winds and below-average air pressure over the continent, leading to strong winds from the west across the Peninsula. This has caused melting along the eastern Peninsula ice, above-average air temperatures over the Weddell Sea, and outflowing winds from the continent, opening the polynyas and hastening ice decline. This wind pattern is summarized by the Southern Annular Mode (SAM) index, a measure of the intensity of the circumpolar winds; this has been in a positive phase for most of 2022 and has been quite strong in the last quarter of the year.