April sea ice loss in the Arctic proceeded at a near-average rate overall, with the majority of ice losses in the Bering Sea and Sea of Okhotsk. In the Antarctic, sea ice grew faster than average, roughly evenly around the entire continent. Both hemispheres are well below the 1981 to 2010 reference period average, but neither are near record-low extents.

Overview of conditions

Figure 1a. Arctic sea ice extent for April 2024 was 14.12 million square kilometers (5.45 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 5, 2024, along with daily ice extent data for four previous years and the record low year. 2024 is shown in blue, 2023 in green, 2022 in orange, 2021 in brown, 2020 in magenta, and 2012, the record low year, 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 average Arctic sea ice extent for April 2024 was 14.12 million square kilometers (5.45 million square miles), placing it sixteenth lowest in the passive microwave satellite record (Figure 1a and 1b). As of the beginning of May, extent is well below average in the Sea of Okhotsk, and slightly below average in the Bering and Barents Seas and off the coast of Labrador. Ice is near the average position along the eastern coast of Greenland.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level relative to the 1991 to 2020 reference period, in degrees Celsius, for April 2024. Yellows and reds indicate above average temperatures; blues and purples indicate below average temperatures.

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

Figure 2b. This plot shows the average sea level pressure in the Arctic in millibars for April 2024. Yellows and reds indicate above average air pressures; blues and purples indicate below average air pressures.

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

The global average temperature in April was at a record high in many assessments. By contrast in the Arctic, April 2024 temperatures at the 925 hPa level (about 2,500 feet above the surface) were below average by 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) along the Siberian coast and northwestern coast of Scandinavia. Markedly warm conditions were the rule over most of Canada and northern Greenland (Figure 2a). The regions near Hudson Bay and along Peary Land on the north coast of Greenland were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) above the 1991 to 2020 climate reference period.

The atmospheric pattern for April featured high sea level pressure centered over the Barents Sea but lower pressure over most of the rest of the Arctic Ocean (Figure 2b). In Hudson Bay and Greenland, pressures were relatively high. The pattern in March that favored faster outflow of ice through Fram Strait did not persist into April.

April 2024 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2024 shows a decline of 2.4 percent per decade.

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

Including 2024, the downward linear trend in April mean monthly sea ice extent was 36,000 square kilometers (14,000 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, April has lost 1.61 million square kilometers (622,000 square miles) of sea ice, which is roughly equivalent to six times the size of Colorado. April 2024 had the highest sea ice extent for the month in 12 years.

Lightening the mood in the Arctic

Figure 4. This set of figures shows the timing of under-ice algae bloom onset from blending CryoSat-2 (CS2), Sentinel-3 (S3), and ICESat-2 (IS2)-derived sea ice thickness data. The color bar refers to the day of the year (DOY) that enough light passes through the snow cover and sea ice to spark an algae bloom. S3 data were only available in 2019 and 2020. Missing data in 2021 and 2022 around 80N reflects missing albedo data in the Advanced Very High Resolution Radiometer (AVHRR) APP-X data product.

Credit: Stroeve et al. 2024
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When sea ice extent shrinks and thins, and there is less snow cover, more light enters the water deeper. Light is a primary driver for sea ice algae and phytoplankton blooms, which form the base of the Arctic marine foodchain. To determine the timing of when enough light is present to initiate an ice algal bloom, NSIDC scientist Julienne Stroeve and others took existing satellite data products and combined them with information on light extinction properties through snow and ice. Light extinction implies the amount of dimming as light passes through ice, beginning at 100 percent (high) and dropping to 10 percent at the base of the ice. This has only been possible recently, with the development of accurate daily sea ice thickness products blended from CryoSat-2, Sentinel-3, and the Ice, Cloud and land Elevation Satellite-2 (ICESat-2).

Figure 4 illustrates the timing of bloom onset from 2019 to 2022, highlighting large year-to-year variability that reflects variability in snow depth over sea ice. In 2019, for example, bloom onset occurred at the end of February in the Beaufort Sea, whereas in 2022 the bloom onset occurred between mid-March to early April. In general, bloom onset starts about a month earlier in the marginal ice zone than it does in the central Arctic Ocean.

Antarctic note

Figure 5a. Antarctic sea ice extent for April 2024 was 6.19 million square kilometers (2.39 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

Figure 5b. The graph above shows Antarctic sea ice extent as of May 5, 2024, along with daily ice extent data for four previous years and the record high year. 2024 is shown in blue, 2023 in green, 2022 in orange, 2021 in brown, 2020 in magenta, and 2014, the record high year, 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

April is the month of most rapid ice growth in the south. Sea ice expanded relatively uniformly around the continent, but remained below the average extent in the eastern Weddell Sea and the Ross and western Amundsen Seas (Figure 5a). Sea ice grew at a slightly above-average rate, totaling about 3.6 million square kilometers (1.39 million square miles) in April, whereas the 1981 to 2010 average ice growth is 3.20 million square kilometers (1.24 million square miles) (Figure 5b).

Above-average temperatures of 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) continued to persist in western Dronning Maud Land but below-average temperatures of 4 to 7 degrees Celsius (7 to 13 degrees Fahrenheit) prevailed in the eastern Amundsen Sea and much of the Wilkes Land coast.

Conditions leading to Antarctica’s record low sea ice in 2023

Figure 6. This figure shows climate and ocean conditions in July 2023 for the Antarctic sea ice region. The top left shows sea ice concentration difference from average in percent. The top right shows ocean temperature difference from average in degrees Celsius (1.8 degrees Fahrenheit equals 1 degree Celsius). The lower left shows sea level pressure difference from average in hectopascals (roughly equal to a millibar). The lower right shows near-surface air temperature difference from average (at 2 meters or 6.5 feet above the surface).

Credit: M. Ionita, 2024
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In July 2023, mid-winter Southern Ocean sea ice fell more than 2.40 million square kilometers (927,000 square miles) below the long-term average, a huge shortfall that revised scientific perceptions of what was possible in the Antarctic climate system. A recent paper written by Monica Ionita from the Alfred Wegner Institute Helmholtz Center for Polar and Marine Research placed the cause of the extreme event with a persistent threefold pattern of alternating low and high air pressure centers surrounding the continent. This pattern, known as “zonal wave-3,” transports warmth and moist air toward the Antarctic coast, suppressing sea ice formation and leading to exceptional anomalies in air temperature and ocean temperature.

Ionita, M. 2024. Large-scale drivers of the exceptionally low winter Antarctic sea ice extent in 2023. Frontiers in Earth Science. doi: 10.3389/feart.2024.1333706.

Stroeve, J, et. al. 2024. Mapping potential timing of ice algal blooms from satellite. Geophysical Research Letters. doi: 10.1029/2023GL106486.

During February, Arctic sea ice extent increased along the lower 10 percent interdecile value, with the average monthly extent tied for fifteenth lowest in the satellite record. Temperatures were above average over the central Arctic, but still well below freezing. Antarctic sea ice extent reached its seasonal minimum, tied for the second lowest extent in the satellite record.

Overview of conditions

Figure 1a. Arctic sea ice extent for February 2024 was 14.61 million square kilometers (5.64 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of March 3, 2024, along with daily ice extent data for four previous years and the record low year. 2023 to 2024 is shown in blue, 2022 to 2023 in green, 2021 to 2022 in orange, 2020 to 2021 in brown, 2019 to 2020 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Arctic sea ice extent in February tracked near the lowest decile of 10 percent for much of the month. The February 2024 extent of 14.61 million square kilometers (5.64 million square miles) (Figure 1a) was 690,000 square kilometers (266,000 square miles) below the 1981 to 2010 average extent of 15.30 million square kilometers (5.91 million square miles) and 640,000 square kilometers (247,000 square miles) above the lowest February extent observed in 2018. It was tied with 2022 as the fifteenth lowest over the 46-year satellite data record (Figure 1b). Ice growth occurred primarily within the Sea of Okhotsk, the Bering Sea, and to a lesser extent in the Barents Sea. Overall, the ice cover in February was more expansive than average in the Sea of Okhotsk and below average in the Barents, Bering, and Labrador Seas. Elsewhere, the ice edge was near average for this time of year.

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for February 2024. Yellows and reds indicate above average temperatures; blues and purples indicate below average temperatures.

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

Figure 2b. This plot shows the departure from average sea level pressure in the Arctic in millibars for February 2024. Yellows and reds indicate above average air pressures; blues and purples indicate below average air pressures.

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

While temperatures are usually well below freezing over the Arctic Ocean in February, this February they were not as low as is typical for this time of year. Over the central Arctic Ocean, air temperatures at the 925 millibar level (about 2,500 feet above sea level) were up to 10 degrees Celsius (18 degrees Fahrenheit) above average (Figure 2a). Above-average temperatures also extended over Alaska and the Canadian Arctic while below-average temperatures prevailed over much of Siberia.

The unusual warmth near the North Pole stemmed from strong high pressure over Siberia extending into the Laptev Sea (Figure 2b). This high pressure combined with exceptionally below-average sea level pressure over Bering Sea and near Iceland led to a strong pressure gradient that forced relatively warm air over western Eurasia to flow into the central Arctic Ocean and cold Arctic air to flow out into the Bering Sea.

February 2024 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2024 shows a decline of 2.7 percent per decade.

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

The downward linear trend in Arctic sea ice extent for February over the 46-year satellite record is 41,000 square kilometers (16,000 square miles) per year, or 2.7 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, February has lost 1.84 million square kilometers (710,000 square miles) of ice since 1979. This is equivalent to the size of Alaska.

Less ice means more autumn clouds

Figure 4. These plots show average October surface longwave cloud warming for 2008 to 2020 estimated from spaceborne lidar over open water (left) and over sea ice (right). Areas of mixed ocean and sea are indicated in white. Areas under the black lines indicate regions with fewer than 5 years of data for the given surface type.

Credit: Adapted from Figure 3 of Arouf et al., 2023
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As Arctic sea ice declines during summer, the increased absorption of solar energy by the open ocean delays autumn freeze up. Satellite observations reveal that with less autumn sea ice, increased air-sea coupling has led to more low-level clouds over open water areas. Quantifying the radiative effect of this increased cloud cover is challenging. A recent study by colleagues at the University of Colorado Boulder addressed this issue using lidar observations at high resolution from the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. They found large warming at the surface induced by clouds occurs much more frequently over open water than over sea ice during autumn months (Figure 4). Thus, while the ocean heat effect on delayed sea ice growth is well known, these results provide quantitative evidence that Arctic clouds can also delay autumn sea ice formation.

Antarctic summer comes to an end

Figure 5a. The graph above shows Antarctic sea ice extent as of March 3, 2024, along with daily ice extent data for four previous years and the record high year. 2023 to 2024 is shown in blue, 2022 to 2023 in green, 2021 to 2022 in orange, 2020 to 2021 in brown, 2019 to 2020 in magenta, and 2014 to 2015 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 5b. Antarctic sea ice extent for February 2024 was 2.14 million square kilometers (826,000 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
High-resolution image

Figure 5c. This plot shows the departure from average air temperature in the Antarctic at the 925 hPa level, in degrees Celsius, for December 2023 through February 2024. Yellows and reds indicate above average temperatures; blues and purples indicate below average temperatures.

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

Antarctic sea ice extent appears to have reached its seasonal minimum, ending up as tied with 2022 for second lowest in the satellite data record, just above 2023. Thus, the last three years are the three lowest in the 46-year record and the first three years that reached an extent below 2.0 million square kilometers (772,000 square miles). Having three such years in a row is unusual. Extent is especially low in the Ross, Amundsen, and Bellingshausen Seas, whereas over the Weddell Sea and along the East Antarctic coast the ice cover is at average levels (Figure 5b).

This pattern of above-average ice extent in the Weddell Sea coupled with below-average extent in the Ross, Amundsen, and Bellingshausen Seas is broadly consistent with the expected response to atmospheric conditions during an El Niño. However, the atmospheric circulation pattern this year was atypical of El Niño conditions for most of the season. During a typical El Niño, the Amundsen Sea low pressure weakens, allowing for increased advection of warm air and warm sea surface temperatures from lower latitudes to the Ross–Amundsen Seas, while winds from the south to the east of the anticyclone tend to advect cold air to the Weddell Sea (Figure 5c). However, this past austral summer, there was no weakening of the Amundsen Sea Low and average temperatures prevailed over the Weddell Sea. Below average sea level pressure dominated the continent for the first half of the winter, but this changed to a pattern that favored warm winds from the north over the eastern Weddell Sea and the eastern Ross Sea regions. Early melting and ice loss along the eastern side of the Peninsula stopped abruptly in mid-January.

Further reading

Arouf, A., H. Chepfer, J. E. Kay, T. S. L’Ecuyer, and J. Lac. 2024. Surface cloud warming increases as late fall Arctic sea ice cover decreases. Geophysical Research Letters, 51, e2023GL105805, doi:10.1029/2023GL105805.

Kay, J. E. and A. Gettelman. 2009. Cloud influence on and response to seasonal Arctic sea ice loss. Journal of Geophysical Research, 114, D18204, doi:10.1029/2009JD011773.

The end of 2023 had above average sea ice growth, bringing the daily extent within the interdecile range, the range spanning 90 percent of past sea ice extents for the date. Rapid expansion of ice in the Chukchi and Bering Seas and across Hudson Bay was responsible. The Antarctic summer sea ice decline slowed, moving the daily ice extent values above previous record low levels. For the year as a whole, however, low Antarctic sea ice was the dominant feature.

Overview of conditions

Figure 1a. Arctic sea ice extent for December 2023 was 12.00 million square kilometers (4.63 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 January 3, 2024, along with daily ice extent data for four previous years and the record low year. 2023 to 2024 is shown in blue, 2022 to 2023 in green, 2021 to 2022 in orange, 2020 to 2021 in brown, 2019 to 2020 in magenta, and 2012 to 2013 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Average Arctic sea ice extent for December 2023 was 12.00 million square kilometers (4.63 million square miles), ninth lowest in the 45-year satellite record (Figure 1a). Sea ice extent increased by an average of 87,400 square kilometers (33,700 thousand square miles) per day, markedly faster than the 1981 to 2010 average of 64,100 square kilometers (24,700 square miles) per day (Figure 1b). After a delayed start to the freeze-up in Hudson Bay, sea ice formed quickly from west to east across the bay, leaving only a small area of open ocean near the Belcher Islands at month’s end. In the northern Atlantic, sea ice extent remained below average extent, as has been typical for the past decade.

For December overall, 2023 had the third highest monthly gain in the 45-year record at 2.71 million square kilometers (1.05 square miles), behind 2006 at 2.85 million square kilometers (1.10 million square miles) and 2016 at 2.78 million square kilometers (1.07 million square miles).

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 2023. Yellows and reds indicate above average temperatures; blues and purples indicate below average temperatures.

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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for December 2023. Yellows and reds indicate above average air pressures; blues and purples indicate below average air pressures.

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

Warm conditions prevailed over the central Arctic Ocean and Beaufort Sea regions, as well as over Hudson Bay and much of northern Canada, with air temperatures at the 925 millibar level (around 2,500 feet above sea level) 8 to 9 degrees Celsius (14 to 16 degrees Fahrenheit) above the 1991 to 2020 average (Figure 2a). Elsewhere, relatively cool conditions prevailed, with air temperatures 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below average in southwestern Alaska, easternmost Russia, Scandinavia, and southeast Greenland. Cool conditions in the Bering and southern Chukchi Seas explain the rapid ice growth there. By contrast, the warm conditions over Hudson Bay, continuing since November, explain its delayed start of ice formation there.

The atmospheric circulation pattern for December was marked by low sea level pressure over the Gulf of Alaska and northern Europe and high sea level pressure over central Russia (Figure 2b). This pattern led to cold Arctic air flowing across the Chukchi Sea and into the Bering Sea as well as advection of relatively warm air across Canada into the Beaufort Sea.

December 2023 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2023 shows a decline of 3.4 percent per decade.

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

The downward linear trend in Arctic sea ice extent for December over the 45-year satellite record is 43,400 square kilometers (16,800 square miles) per year, or 3.4 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, December has lost 1.97 million square kilometers (761,000 million square miles) of ice since 1979. This is equivalent to three times the size of Texas.

Fast growth of ice cover over Hudson Bay

Figure 4. This animation shows the rapid expansion of sea ice cover in November to December 2023 for Hudson Bay (click to animate).

Credit: Zachary Labe, Princeton University
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As noted above, sea ice formation in Hudson Bay was unusually late, but the ice cover expanded quickly from west to east in mid-December. This is approximately 10 to 20 days later than usual, a result of warm water conditions over the bay extending into late fall. As of early January 2024, a small region of open water persisted near the Belcher Islands, roughly three weeks after freeze-up normally occurs.

Antarctic sea ice: slower decline

Figure 5a. The graph above shows Antarctic sea ice extent as of January 3, 2024, along with daily ice extent data for four previous years and the record high year. 2023 to 2024 is shown in blue, 2022 to 2023 in green, 2021 to 2022 in orange, 2020 to 2021 in brown, 2019 to 2020 in magenta, and 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 5b. Antarctic sea ice extent for December 2023 was 8.67 million square kilometers (3.35 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 5c. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for December 2023. Yellows and reds indicate above average temperatures; blues and purples indicate below average temperatures.

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

At the beginning of December, ice extents were at record low levels. However, the seasonal decline in Antarctic ice extent subsequently slowed. As a result, by the beginning of the new year, extent was only sixth lowest (Figure 5a). Despite the slow ice loss, few areas of the Southern Ocean have above average sea ice extent, and extent is still well below the average for 1981 to 2010 in the Weddell Sea, along the coast of Dronning Maud Land, and in the western Ross Sea (Figure 5b). Typical for this time of year, a large polynya has opened up in front of the Ross and Sulzberger Ice Shelves. Low sea ice concentrations in the Ross Sea and western Amundsen Sea portend upcoming ice extent declines in these areas. Air temperatures were above average over West Antarctica and the Ross Sea by 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) for the month, and over the Bellingshausen Sea by 1 to 2 degrees Celsius (2 to 4 degrees Celsius) (Figure 5c). Dronning Maud Land was above average by up to 2.5 degrees Celsius (4.5 degrees Fahrenheit). Below average conditions prevailed over Wilkes Land, at 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below the 1991 to 2020 reference period.

Looking back at 2023

The extremely low Antarctic sea ice extent for most of the year was the most noteworthy characteristic of either polar region for 2023. At one point in mid-August, southern hemisphere sea ice was more than 1.80 million square kilometers (695,000 square miles) below the previous record low years (2022, 2002, or 1986 depending on the day of year), and more than 2.6 million square kilometers (1.00 million square miles) below the 1981 to 2010 average extent. The difference between 2023 daily extent and the 1981 to 2010 average was greater than 1 million square kilometers (386,000 square kilometers) for nearly the entire year. Several studies have argued that low sea ice extents in recent years for the Southern Ocean represent a response to unusually high temperatures in the upper ocean layer.

In the Arctic, sea ice extent followed a pattern typical of the past decade, with persistently below-average extent in the northernmost Atlantic (Barents and Norwegian Seas) and large summer retreat along the eastern Siberian coast. However, the pace of sea ice decline (e.g. summer minimums or monthly average extents) has slowed since 2012, and the 2012 record low summer minimum has not been surpassed. While explanations have been offered to account for this “hiatus,” notably involving variations on ocean heat transport to the Arctic Ocean, questions remain.

Further reading

Polyakov, I. V., et al. 2023. Fluctuating Atlantic inflows modulate Arctic atlantification. Science. doi: 10.1126/science.adh51

As the long Arctic winter sets in, sea ice extent has increased at a faster than average pace. By the end of October, the ice cover had reached the Siberian coast, while open water persisted along the coasts of the Beaufort and Chukchi Seas. In the Antarctic, the spring decline in extent has been quite slow, but extent at the end of October remains at record low levels for this time of year.

Overview of conditions

Figure 1a. Arctic sea ice extent for October 2023 was 6.37 million square kilometers (2.46 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 November 1, 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 for October 2023 was 6.37 million square kilometers (2.46 million square miles), seventh lowest in the 45-year satellite record (Figure 1a). Overall, during October sea ice extent increased by 119,800 thousand square kilometers (46,300 square miles) per day, which is faster than the 1981 to 2010 average of 89,200 square kilometers (34,400 square miles) per day (Figure 1b). The freeze up was particularly rapid along the Siberian Seas where the ice cover expanded to the coast by the end of the month. Open water remained in the Beaufort and Chukchi Seas at the end of October. Ice growth within the channels of the Canadian Archipelago closed off the Northwest Passage.

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 October 2023. Yellows and reds indicate above average temperatures; blues and purples indicate below 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 October 2023. Yellows and reds indicate above average air pressures; blues and purples indicate below average air pressures.

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

Air temperatures over the Arctic Ocean at the 925 mb level (about 2,500 feet above the surface) were mostly above average during October, particularly in and around the Canadian Archipelago, which saw temperatures of 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) above average (Figure 2a). Temperatures were modestly above average across the pole and over the Laptev and Kara Seas. The Chukchi and East Siberian Seas experienced near-average temperatures while temperatures were below average over the Bering Strait and the Barents and Norwegian Seas.

The atmospheric circulation featured weak high sea level pressure centered over the North Pole and fairly strong low pressure centered on the Norwegian Sea and north-central Siberia (Figure 2b). This pattern created strong winds along the Russian Arctic coast.

October 2023 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2023 shows a decline of 9.5 percent per decade.

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

The downward linear trend in Arctic sea ice extent for October over the 45-year satellite record is 79,300 square kilometers (30,600 square miles) per year, or 9.5 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, October has lost 3.49 million square kilometers (1.35 million square miles) of ice since 1979. This is equivalent to twice the size of Alaska.

Spring breaks slowly in the south

Figure 4. The graph above shows Antarctic sea ice extent as of November 1, 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

As the Antarctic heads toward summer following the record low maximum sea ice extent in September (winter), the rate of ice loss has been a bit slower than average. During October, the 2023 rate of decline was 29,100 square kilometers (11,200 square miles) per day, compared to the average rate of decline of 31,800 square kilometers (12,300 square miles) per day (Figure 4). The total decline in sea ice extent through October was 903,000 square kilometers (349,000 square miles), compared to the October average of 985,000 square kilometers (380,000 square miles).

Nonetheless, extent at the end of October remained at record low levels. The October 31, 2023, extent of 15.79 million square kilometers (6.10 million square miles) is 750,000 square kilometers (290,000 square miles) below the previous October 31 record low, which occurred in 1986. Extent is below average in the Ross Sea region and to the east of the Weddell Sea, as has been the case through most of austral winter. Extent is above average in the Amundsen and Bellingshausen Seas and near-average elsewhere.

Both Arctic and Antarctic sea ice appear to be heading toward their respective seasonal limits, reaching the lowest extent at the end of summer in the north, and the highest extent as winter ends in the south. In the Antarctic, high variability typically characterizes the period around the maximum, but at present the sea ice extent is more than 1 million square kilometers (386,000 square miles) below the previous record low maximum set in 1986.

Overview of conditions

Figure 1a. This figure shows Arctic sea ice concentration for September 13. The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of September 13, 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

Figure 1c. The graph above shows Antarctic sea ice extent as of September 13, 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 1d. Antarctic sea ice extent for September 13, 2023 was 16.94 million square kilometers (6.54 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

Retreat of Arctic sea ice cover has been primarily in the central Arctic region north of the Laptev and East Siberian Seas in an area of low sea ice concentration (Figure 1a). A few large areas of open water are present between several areas of higher-concentration sea ice. On the Pacific side, the Beaufort and Chukchi Seas have very little sea ice remaining; on the Atlantic side, both the Svalbard archipelago and Franz Josef Land are largely ice free (Figure 1a). Both passages of the Northwest Passage are largely clear of ice at the resolution of passive microwave satellite data, but likely have patchy ice remaining. Ice blocks the western end of the Parry Channel near M’Clure Strait, but the ice edge has pulled away from the coast in recent days and it appears that there is a narrow ice-free region along the northwest coast of Banks Island.

Antarctic sea ice grew at a much faster-than-average pace through the first eight days of September, increasing at 65,000 square kilometers (25,000 square miles) per day relative to the 1981 to 2010 average rate of 25,000 square kilometers (9,700 square miles) per day (Figure 1c). Much of this expansion occurred in the northeastern Ross Sea and along the Weddell Sea ice front (Figure 1d). However, growth slowed after September 8. If no further net growth occurs, the sea ice maximum will be below 17 million square kilometers (6.56 million square miles) for the first time in the satellite record, and about one million square kilometers (386,000 square miles) below the previous record low maximum of 1986. The five low maximum sea ice extents for Antarctica include 1986, 2002, 2017, 1989, and 2022. High variability is typical of the sea ice maximum period, and further growth is likely from storms or high winds along the vast circumpolar sea ice edge.

Conditions in context

Figure 2a. This plot shows average sea level pressure in the Arctic in millibars for September 1 to 11, 2023. Yellows and reds indicate above average air pressure; blues and purples indicate below average pressure.

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 September 1 to 11, 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 2c. This plot shows the departure from average sea level pressure in the Antarctic in millibars for September 1 to 11, 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

Figure 2d. This plot shows the departure from average air temperature in the Antarctic at the 925 hPa level, in degrees Celsius, for September 1 to 11, 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

For the first two weeks of September, high air pressure prevailed over northern Siberia, with low pressure over Greenland, which created significant winds along the Eurasian coast (Figure 2a). Air temperatures were generally above average in Western Europe and Scandinavia, and below average in eastern Siberia (Figure 2b). The outlook for a few more days is for continued warm conditions and airflow that may cause further contraction of the low-concentration sea ice.

In Antarctica, a strong high-pressure area over the Peninsula region with counterclockwise airflow helped push sea ice outward along the northwestern Weddell Sea, where the air temperature was quite low (Figure 2c). Low air pressure and below average temperatures in the central and western Ross Sea helped push sea ice outward in the eastern Ross Sea (Figure 2d). Storms will very likely cause the sea ice edge to fluctuate.

Arctic sea ice continues to decline at a near-average pace, with ice extent twelfth lowest in the satellite record at this time. Antarctic sea ice by contrast is growing at far below-average rates and is at an unprecedently low level for this time of year relative to the 45-year data set.

Overview of conditions

Figure 1a. The graph above shows Arctic sea ice extent as of July 17, 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

Figure 1b. Arctic sea ice extent for July 17, 2023 was 8.27 million square kilometers (3.19 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 1c. This map shows a large opening in the East Siberian Sea as well as several smaller openings within the pack further north of the polynya, and areas of low concentration in the Beaufort Sea north of Alaska. Sea ice concentration data are from Advanced Microwave Scanning Radiometer 2 (AMSR2) imagery.

Credit: University of Bremen
High-resolution image

During the first half of July, Arctic sea ice extent declined at a near-average pace of 81,800 square kilometers (31,600 square miles) per day, just below the 1981 to 2010 average of 86,200 square kilometers (33,300 square miles) per day (Figure 1a). As of this post, sea ice in the Arctic is about 1.31 million square kilometers (506,000 square miles) below the 1981 to 2010 reference period, and ice extent for July 17 is twelfth lowest in the 45-year satellite record.

However, several regions have far below average extent, including Hudson Bay, which according to the satellite data became ice-free quite early this year, the Kara Sea, and the Beaufort Sea (Figure 1b). Sea ice extent and concentration from the higher-resolution Advanced Microwave Scanning Radiometer 2 (AMSR2) data processed by the University of Bremen shows a large opening in the East Siberian Sea as well as several smaller openings within the pack further north of the polynya, and areas of low concentration in the Beaufort Sea north of Alaska (Figure 1c). A large polynya has also formed in the Kara Sea near Severnaya Zemlya.

To date since June 1, 3.82 million square kilometers (1.47 million square miles) of ice have melted.

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 July 1 to 16, 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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Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for July 1 to 16, 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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Air temperatures at the 925 millibar level (approximately 2,500 feet above the surface) over the Arctic Ocean for the first half of July ranged from 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) below average over the Laptev Sea, contrasting with above-average values of 2 to 7 degrees Celsius (4 to 13 degrees Fahrenheit) in a band extending from northeast of Greenland to the Beaufort Sea off the coast of Canada (Figure 2a). Particularly warm conditions were the rule near the MacKenzie River delta. Another area of warm conditions existed in the southern Baffin Bay and the Labrador coast. The atmospheric circulation for the first half of July was characterized by generally low pressure over the Siberian side of the Arctic Ocean, and high air pressure in a broad area covering Greenland, Fram Strait, and the northern Barents Sea (Figure 2b).

Smoke on the Arctic water

Figure 3. This true color composite image from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) on July 16 shows the North Pole at the center of the image, with Greenland pointing down.

Credit: NASA Worldview
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A relatively clear-sky image from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on July 16 provides a visual glimpse of the condition of sea ice and surrounding areas (Figure 3). Open water is visible in the East Siberian Sea with lower concentration ice extending toward the east, confirming the concentration pattern seen in the AMSR2 imagery (Figure 1c). Another interesting feature of the MODIS image is the wildfire smoke over Canada, which has drifted into the US causing air quality issues. There is also wildfire smoke in eastern Siberia. Some smoke from both areas have drifted over coastal sea ice areas. Such smoke can reduce the amount of solar energy reaching the sea ice surface, which could slow melt. However, as smoke particles fall onto the ice, they darken the ice surface, causing it to absorb more of the sun’s energy, which would enhance melt. Given the limited region of sea ice covered by smoke, any effect is unlikely to substantially impact this year’s melt.

Antarctic sea ice extent

Figure 4a. The graph above shows sea ice extent for February 18 to November 2 for every year in the 45-year satellite data set, with 2023 shown in blue. The dashed red line is the 2022 ice extent, which was the former record summer minimum low before 2023.

Credit: Ted Scambos, Cooperative Institute for Research in Environmental Sciences
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Figure 4b. Antarctic sea ice extent for July 17, 2023 was 13.45 million square kilometers (5.19 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Figure 4c. This figure shows the monthly Antarctic sea ice extent (SIE) anomaly (difference relative to the 1981 to 2010 average) for January 1979 to July 2023. The x-axis shows years, 1979 through 2023. The y-axis shows months of the year from January (bottom) to December (top). Red shades indicate higher than average extent, while blue shades indicate lower than average extent, with darker shades corresponding to larger differences.

Credit: Julienne Stroeve, National Snow and Ice Data Center
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Sea ice surrounding the Antarctic continent continues to be exceptionally low. Antarctic ice extent as of mid-July is more than 2.6 million square kilometers (1.00 million square miles) below the 1981 to 2010 average, an area nearly as large as Argentina or the combined areas of Texas, California, New Mexico, Arizona, Nevada, Utah, and Colorado. It is 1.6 million square kilometers (618,000 square miles) below the previous record low extent for the date, set in 2022 (Figure 4a). Low ice extent is present nearly everywhere, but particularly in the northern Weddell Sea, western Ross Sea, and southern Bellingshausen Sea (Figure 4b). Above average extent is prevalent in the Amundsen Sea.

The research community has been discussing the causes for the sudden turnabout in Antarctic sea ice extent, from a weakly positive linear trend from 1978 to 2015 to a strongly negative trend since 2016; and the events of 2022 and 2023 have garnered much attention. Many recent studies point to changing conditions in the upper ocean layer. Warm water from the north has mixed into this layer, which tends to increase the stratification of the ocean. This appears to coincide with when sea ice went from record high extents to low extents beginning in September 2016, and still lower extents in 2023.

Further reading

Eayrs, C., X. Li, M. N. Raphael, and D. M. Holland. 2021. Rapid decline in Antarctic sea ice in recent years hints at future change. Nature Geoscience. doi:10.1038/s41561-021-00768-3

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
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.

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
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 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
High-resolution image

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
High-resolution image

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
High-resolution image

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.