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
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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
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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
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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
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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
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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
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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
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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
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.

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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.

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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.

As October drew to a close, freezing progressed rapidly in the Laptev Sea. In the Antarctic, where spring is slowly unfolding, overall ice extent is low, with patterns suggesting a strong persistent low atmospheric pressure in the Amundsen Sea.

Overview of conditions

Figure 1a. Arctic sea ice extent for October 2022 was 6.61 million square kilometers (2.55 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Figure 1b. The graph above shows Arctic sea ice extent as of November 2, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The October 2022 average Arctic sea ice extent was 6.61 million square kilometers (2.55 million square miles). This is the eighth lowest in the satellite record (Figure 1a). Extent was 1.74 million square kilometers (672,000 square miles) below the 1981 to 2010 average of 8.35 million square kilometers (3.22 million square miles) and 1.28 million square kilometers (494,000 square miles) above the record minimum set in 2020 of 5.33 million square kilometers (2.06 million square miles).

Ice extent increased at a below average rate at the beginning of the month, and open water persisted for some time in the Laptev Sea, whereas the East Siberian Sea was among the first regions to freeze up. In the last ten days of the month, ice extent rapidly increased (Figure 1b) as the Laptev Sea iced over. The delayed freeze up in the Laptev Sea could be partly a result of ocean heating from the extended period of open water this past spring and summer. However, slow freeze up in this region in recent years is also consistent with observations of eddies within the Arctic Circumpolar Boundary Current that maintain a generally upward ocean heat flux, bringing warm Atlantic water along the eastern Arctic continental slope. The Arctic Circumpolar Boundary Current is a shallow, 200- to 400-meter-deep (660 to 1,300 feet) eastward-flowing current that follows the edge of the continental shelf and carries warm water at 2 to 3 degrees Celsius (36 to 37 degrees Fahrenheit) in shallow depths around the Arctic Ocean. The configuration of the continental shelf in the Russian Arctic brings this water very near the coastal Laptev Sea.

At the end of the month, extent remained below average in the Chukchi Sea on the Pacific side of the Arctic, and also in the Barents and Kara Seas on the Atlantic side.

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 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 October 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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Air temperatures during October at the 925 millibar level (approximately 2,500 feet above the surface) were near to above average over most of the Arctic Ocean (Figure 2a). The largest departures from average for this time of year were over the Kara Sea, where air temperatures averaged for October remained above freezing.

The average atmospheric circulation pattern was dominated by below average sea level pressure over nearly the entire Arctic (Figure 2b). Pressures were as much as 10 to 12 millibars below average over the Chukchi and East Siberian Seas and stretching across the pole. This pattern is reflected in the persistence of positive values of the Arctic Oscillation Index for most of the month. When the Arctic Oscillation is in its positive mode, pressures are below average over the Arctic, but above average over the Northern Hemisphere mid latitudes.

October 2022 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2022 shows a decline of 9.6 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in October sea ice extent over the 45-year satellite record is 80,400 square kilometers (31,000 square miles) per year, or 9.6 percent per decade relative to the 1981 to 2010 average. Based on the linear trend, since 1979 October has lost 3.46 million square kilometers (1.34 million square miles). This equivalent to about twice the size of the state of Alaska.

Arctic sea ice loss may make El Niños more common

Figure 4. These plots show histograms of El Niño indices associated with Arctic sea ice loss experiments in climate model runs. The left histogram (a) shows the zonal sea surface temperature (SST) gradient in the equatorial Pacific that is defined as the average SST over the Niño 3.4 region (5S-5N, 170W-120W) minus the Maritime Continent region (5S-5N, 110E-160E). The histogram on the right (b) shows the meridional SST gradient in the eastern equatorial Pacific that is defined as the average SST over 5N-10N, 160W-100W minus 2.5S-2.5N, 160W-100W. The vertical bars denote 20-year periods of constant Arctic sea ice in experiments using the US National Center for Atmospheric Research Community Earth System Model (CESM). Gray is the historical period (1980 to 1999); blue is the future period of moderate ice loss (2020 to 2039); and red is the future period of seasonally ice-free conditions (2080 to 2099). Each bin represents 0.5 standard deviation of the corresponding SST anomalies or gradients. Black dashed lines represent 1.5 (strong El Niño) and 2 (extremely strong El Niño) standard deviations.

Credit: Jiping Liu et al. 2022, adapted by NSIDC
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El Niño is an important departure in ocean temperatures along the equator, linked to weakened trade winds. During an El Niño, the cold upwelled waters along the coast of the Americas and much of the eastern parts of the tropical Pacific are replaced by warmer water. This can have global impacts on weather, ecosystems, and economies around the world by shifting the Pacific jet stream southwards. In North America, this usually results in drier and warmer conditions than usual in the northern areas, and wetter conditions in the south. While episodes of El Niño typically occur every two to seven years and can last several months to more than a year, climate model simulations by colleagues at the University of Albany suggest that the frequency of El Niño events could increase by 35 percent by the end of this century if the Arctic Ocean loses its summer ice cover.

This link was found to result from increased heat transfer from the ocean to the atmosphere in the absence of sea ice, intensifying low-pressure systems in the Bering Sea (in the area of the Aleutian Low). Lower sea level pressure increases wind speeds that may oppose trade winds, bringing warm western Pacific water towards the east. Another possible mechanism is that as the Arctic Ocean warms from losing its sea ice cover, ocean currents weaken from the south that bring warm water from the eastern Pacific toward the Arctic. Analysis with other climate models is necessary to test the robustness of these connections.

The Antarctic

Figure 5. The graph above shows Antarctic sea ice extent as of November 2, 2022, along with daily ice extent data for four previous years and the record high year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 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 seasonal Southern Ocean sea ice maximum extent was reached on September 16, at 18.19 million square kilometers (7.02 million square miles). This was the fourth lowest sea ice maximum in the satellite record, behind 1986, 2002, and 2017. Low sea ice extent has continued to persist, and the springtime decline in austral ice extent has proceeded at an above average pace. At month’s end, Antarctic sea ice was nearing record-low daily ice extents for the date.

Extent is far below average in the Bellingshausen Sea, and far above average in the Amundsen and eastern Ross Seas, a pattern indicative of a strong Amundsen Sea Low. Sea level pressures in the region have been 8 to 12 millibars below average. However, sea ice extent is also low along the Wilkes Land coast, where air temperatures have been 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above average.

Further reading

Aksenov, Y., V. V. Ivanov, A. G. Nurser, S. Bacon, I. V. Polyakov, A. C. Coward, A. C. Naveira‐Garabato, and A. Beszczynska-Moeller. 2011. The Arctic circumpolar boundary current. Journal of Geophysical Research: Oceans. doi:10.1029/2010JC006637.

Liu, J., M. Song, Z. Zhu, et al. 2022. Arctic sea-ice loss is projected to lead to more frequent strong El Niño events. Nature Communications. doi:10.1038/s41467-022-32705-2.

Pnyushkov, A., I. V. Polyakov, L. Padman, and A. T. Nguyen. 2018. Structure and dynamics of mesoscale eddies over the Laptev Sea continental slope in the Arctic Ocean. Ocean Science. doi:10.5194/os-14-1329-2018.

The sun is about to set for the winter at the North Pole, and so the 2022 sea ice melt season is coming to an end. As of September 19, 2022, Arctic sea ice extent stood at 4.68 million square kilometers (1.81 million square miles), placing it ninth lowest in the satellite record for the date. The high-latitude polynyas have frozen over.

Overview of conditions

Figure 1. Arctic sea ice extent for September 19, 2022 was 4.68 million square kilometers (1.81 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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As of September 19, 2022, Arctic sea ice extent stood at 4.68 million square kilometers (1.81 million square miles), placing it ninth lowest in the satellite record for the date. Between September 1 and September 19, the Arctic lost a total of 522,000 square kilometers (202,000 square miles) of ice, at an average rate of 27,500 square kilometers (10,600 square miles) per day. This was slightly faster than the average daily loss rate over this period. As of September 19, sea ice extent was tracking close to the levels observed in 2010, and the spatial pattern of sea ice extent is similar. As seen in Advanced Microwave Scanning Radiometer 2 (AMSR2) imagery, an island, or patch, of apparently fairly thick ice has separated from the main pack in the East Siberian Sea. Another smaller isolated patch is present in the Beaufort Sea. The Northern Sea Route and the southern (Amundsen’s) route through the Northwest Passage remain open and will likely remain so for several more weeks. The northern route through the Northwest Passage still has some scattered areas of pack ice not picked up in satellite passive microwave imagery.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 19, 2022, along with daily ice extent data for four previous years and the record low year. 2022 is shown in blue, 2021 in green, 2020 in orange, 2019 in brown, 2018 in magenta, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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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, from September 1 to 18, 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 2c. This plot shows average sea level pressure in the Arctic in millibars from September 1 to 18, 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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Air temperatures over the central Arctic Ocean at the 925 hPa level (about 2,500 feet above the surface), averaged from September 1 through September 18 were from 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above the 1991 to 2020 reference period over most of the North American side of the Arctic, but up to 7 degrees Celsius (13 degrees Fahrenheit) above average over the Greenland Ice Sheet (Figure 2b).

The sea level pressure pattern averaged over the same time period (Figure 2c) was dominated by low pressure extending eastward across Eurasia, Alaska, and into eastern Canada, contrasting with high pressure over the remainder of the Arctic, especially west of Scandinavia and over southern Greenland. The low pressure center over eastern Canada, paired with the high pressure over southern Greenland, has been a somewhat persistent pattern in the first half of September. Winds from the south between the pressure centers and the high average temperature over northern Greenland can be related to the prominent early September melt event over the ice sheet (see Greenland Ice Sheet Today).

A surprising observation

Figure 3. While traveling back from Reykjavik, Iceland, in late August, Arctic Sea Ice News & Analysis contributor Mark Serreze observed a patch of sea ice just off the eastern coast of southern Baffin Island. Small, diffuse patches of sea ice can linger through the summer if conditions are favorable, but they are difficult to detect in satellite imagery.

Credit: Mark Serreze, NSIDC
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While traveling back from the International Glaciological Society International Symposium on Ice, Snow and Water in a Warming World in Reykjavik, Iceland, in late August, Arctic Sea Ice News & Analysis contributor Mark Serreze, while looking for icebergs on the blue ocean out the window of the Iceland Air 757, observed a rather surprising patch of sea ice just off the eastern coast of southern Baffin Island. Such small, diffuse patches—the last remnants of the winter ice pack—can linger through the summer if conditions are favorable, but they are very difficult to detect in satellite imagery.

Arctic sea ice thickness study

Figure 4. This animation shows Arctic sea ice thickness from October 2010 to July 2020. Images are from the European Space Agency’s CryoSat-2, which for the first time include summer sea ice thickness.

Credit: Jack Landy
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A new year-round Arctic sea ice thickness dataset based on observations from the European Space Agency CryoSat-2 mission was released this week. Meltwater ponds accumulating at the ice surface previously prevented researchers from generating valid sea ice thickness data from CryoSat-2 during the summer melt season. Only estimates of sea ice thickness during the Arctic winter growth season were available.

New methods, including deep machine learning and model simulations of the satellite radar altimeter, have now enabled accurate measurements of the sea ice freeboard— the height of the ice above the ocean surface—to be obtained from the archive of CryoSat-2 Arctic summer observations dating back to 2011 (Figure 4, to animate). By accounting for snow that weighs down the sea ice, using data from a snow evolution model available at the NASA National Snow and Ice Data Center Distributed Active Archive Center, the ice freeboards for winter and summer months were converted to a 10-year gap-free sea ice thickness record.

In the study, it was discovered that new CryoSat-2 sea ice thickness observations from the early summer, in May and June, correlate closely with the pan-Arctic sea ice extent in the following September. Through the ice-albedo feedback, the thickness of sea ice floes at the start of the melt season dictate how long they survive during summer. Thick ice floes melt less quickly and can survive for longer, whereas thin ice floes melt away, exposing the darker ocean and accelerating further melt. This demonstrates a strong link between spring sea ice thickness and the end-of-summer sea ice extent.

Antarctic recovery

Figure 5. Antarctic sea ice extent for September 19, 2022 was 18.14 million square kilometers (7.00 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Antarctic sea extent is nearing it seasonal maximum. While extent was tracking at record or near record lows since early June, there has been a recent spurt in growth, and extent has reached the tenth percentile for this time of year, still well below average but no longer near the record lowest maximum.

Further reading

Landy, J. C., G. J. Dawson, M. Tsamados, M. Bushuk, J. Stroeve, S. Howell, T. Krumpen, D. Babb, A. Komarov, H. Heorton, H. J. Belter, and Y. Aksenov. 2022. A year-round satellite sea-ice thickness record from CryoSat-2. Nature. doi:10.1038/s41586-022-05058-5.