Western Arctic leads the way on springtime decline

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 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

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, 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 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

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

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 | High-resolution image

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
High-resolution image

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 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

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|High-resolution image

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
High-resolution image

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.

Arctic sea ice: Walking on sunshine

Following the 2024 maximum sea ice extent on March 14, Arctic ice extent has declined slowly such that 2024 March average is the fifteenth lowest in the passive microwave satellite record. The atmospheric circulation pattern for March 2024 featured a strong pressure gradient across Fram Strait, likely promoting strong winds from the north and therefore strong sea ice export out of the Arctic. An update on sea ice age reveals continued scarcity of the oldest age classes. A new study highlights the uncertainty as to when a seasonally ice-free Arctic Ocean can be expected.

Overview of conditions

Map of Arctic sea ice extent for March 2024

Figure 1a. Arctic sea ice extent for March 2024 was 14.87 million square kilometers (5.74 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

sea ice extent graph as of April 2, 2024 and other years

Figure 1b. The graph above shows Arctic sea ice extent as of April 2, 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 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 average ice extent for March 2024 is 14.87 million square kilometers (5.74 million square miles), fifteenth lowest in the passive microwave satellite record (Figure 1a). As of the beginning of April 2024, Arctic sea ice extent had dropped by about 278,000 square kilometers (107,000 square miles) below the March 14 maximum (Figure 1b). Extent is notably low only in the Sea of Okhotsk, Barents Sea, Labrador Sea, and Davis Strait. Extent is near average in the Bering Sea, counter to the pattern of below average extent in this region characterizing many recent years.

Conditions in context

Air temperature over Arctic for March as difference from average

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for March 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

Average sea level pressure over Arctic for March 2024

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for March 2024. 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 for March 2024 at the 925 hPa level (about 2,500 feet above the surface) were below average in the Barents Sea and along the Eurasian coast at 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) contrasting with above average values of 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) over the Canadian Arctic Archipelago, Greenland, and Baffin Bay (Figure 2a). This was attended by an unusual atmospheric circulation pattern at sea level (Figure 2b), with high pressure over the North American side of the Arctic and low pressure centered over the Kara Sea, leading to a strong intervening pressure gradient across the Fram Strait. This implies strong winds from the north directed down the strait, which likely favored a strong export of sea ice out of the Arctic Ocean. Whether this pattern continues to persist bears watching.

March 2024 compared to previous years

Graph showing downward linear trend of Arctic sea ice extent

Figure 3. Monthly March 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 March sea ice extent is 37,000 square kilometers (14,000 square miles) per year, or 2.4 percent per decade relative to the 1981 to 2010 average. Since 1979, Arctic sea ice loss in March is 1.68 million square kilometers (649,000 square miles), which is roughly equivalent to the size of the state of Alaska or the country of Iran.

Update on sea ice age

arctic sea ice age maps and graphs

Figure 4. The top maps show sea ice age for the week of March 11 to March 17 for (a) 1984 and (b) 2024. The bottom graph is a timeseries of the percent of the sea ice extent within the Arctic Ocean domain (inset map) for the same time period from 1984 through 2024; color categories are the same as in the maps. Data and images from NSIDC EASE-Grid Sea Ice Age, Version 4 (Tschudi et al., 2019a) and Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1.

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

With the passage of the seasonal maximum sea ice extent, it is appropriate to provide an updated assessment of sea ice age. Older, multiyear ice (ice that has survived at least one melt season) is generally thicker and more resistant to melting completely during the upcoming melt season than first-year ice, which represents ice growth of the previous autumn and winter. As seen in the figure, first-year ice dominates, as it has for the past several years. The extent of multiyear ice is lower than last year, mostly because of less second-year ice (one- to two-year-old ice that has survived two melt seasons), but it is within the ranges that have been seen since 2008. The oldest ice (greater than four-years old) has been at very low levels since 2012 and is slightly lower than last year.

Projections of an ice-free Arctic Ocean

Arctic sea ice free projections based on various scenarios and definitions

Figure 5. These charts show different probabilities of ice-free conditions in a given year and month for selected climate models and emission scenarios. The earliest ice-free conditions can be inferred when any probability of ice-free conditions exists, whereas consistently ice-free conditions start to exist when the probability in a given year reaches the likely category. Probabilities are provided for different greenhouse gas emission scenarios with SSP5-8.5 representing the most aggressive emission scenario and SSP1-2.6 the most modest. There are large differences in how likely an ice-free Arctic is to occur in the months of a given year depending on the degree of emissions and climate warming.

Credit: Jahn et al. 2024
High-resolution image

Colleagues Alexandra Jahn and Jen Kay, from the University of Colorado Boulder, and Marika Holland from the National Center for Atmospheric Research recently synthesized our current understanding of the timing and regional variability of an ice-free Arctic. In reviewing the literature, they find that a variety of different definitions of “ice-free” conditions have been used in the past, with impacts on their projected timing. For example, ice-free conditions based on sea ice area occur usually 10 years prior to ice-free conditions based on sea ice extent. Furthermore, they identify a need to clearly distinguish between projections of the first occurrence of ice-free conditions, based on the monthly average data, and consistently ice-free conditions, based on smoothed monthly averages, which occur about 10 years later than the first ice-free conditions. Using sea ice area, the earliest ice-free conditions in the September monthly average are likely to occur by 2050, but could occur as early as the late 2020s and 2030s under all greenhouse gas emission trajectories. Ice-free conditions for at least a day in September are expected approximately four years earlier on average, with the possibility of preceding the monthly average metric by over 10 years. Consistently ice-free September conditions are anticipated by mid-century (2035 to 2067) under all emission trajectories. However, future emission trajectories will determine how often and for how long the Arctic Ocean could be ice free in the future, with a possibility of ice-free conditions for nine months of the year by 2100 in some years under the high emission scenario. Future research is needed on the impact of different model selection and refinement methods on sea ice projections, as well as on the impacts of different lengths of ice-free conditions on the climate system and the ecosystem.

Antarctic note

Arctic sea ice extent in 2024 and other years

Figure 6. The graph above shows Antarctic sea ice extent as of April 2, 2024, along with daily ice extent data for four previous years and 2014, the record maximum year. 2024 is shown in blue, 2023 in green, 2022 in orange, 2021 in brown, 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

Antarctic sea ice extent expanded slowly in mid-March after reaching its summer minimum extent on February 21, lagging behind many of the years in the satellite record and ending the month tied with several other years for third lowest. Ice extent is particularly low in the eastern Ross Sea and western Amundsen Sea region, and in the eastern Bellingshausen Sea. Air temperatures have been near-average over much of the sea ice areas, but up to 3 degrees Celsius (5 degrees Fahrenheit) above average in the eastern Ross Sea and western Amundsen Sea region, and below average off the coast of Adelie Land by about the same amount.

Further reading

Jahn, A., M. M. Holland, and J. E. Kay. 2024. Projections of and ice-free Arctic Ocean. Nature Reviews Earth and Environment. doi:10.1038/s43017-023-00515-9.

Arctic sea ice reaches a below-average maximum

Arctic sea ice has likely reached its maximum extent for the year, at 15.01 million square kilometers (5.80 million square miles) on March 14. The 2024 maximum is the fourteenth lowest in the 46-year satellite record.

Overview of conditions

Map of arctic sea ice extent on March 14

Figure 1. Arctic sea ice extent for March 14, 2024, was 15.01 million square kilometers (5.80 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On March 14, 2024, Arctic sea ice likely reached its maximum extent for the year, at 15.01 million square kilometers (5.80 million square miles), the fourteenth lowest extent in the satellite record. This year’s maximum extent is 640,000 square kilometers (247,000 square miles) below the 1981 to 2010 average maximum of 15.65 million square kilometers (6.04 million square miles) and 600,000 square kilometers (232,000 square miles) above the lowest maximum of 14.41 million square kilometers (5.56 million square miles) set on March 7, 2017.

The date of the maximum this year, March 14, was two days later than the 1981 to 2010 average date of March 12.

Conditions in context

graph of arctic sea ice extent for March 14, 2024 and other years

Figure 2. The graph above shows Arctic sea ice extent as of March 14, 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 2011 to 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

The ice growth season ended with near average sea ice extent in Baffin Bay, average extent in the Bering Sea, above average in the northern portion of the Sea of Okhotsk and Greenland Sea, and below average in the Barents Sea. Extent was well below average in the Gulf of St. Lawrence and the southern portion of the Sea of Okhotsk.

Since the maximum on March 14, extent has dropped about 160,000 square kilometers (62,000 square miles), with losses in the northern portion of the Sea of Okhotsk and the Bering Sea. These losses have been offset by gains in the Barents Sea and Gulf of St. Lawrence.

The downward linear trend in Arctic sea ice maximum extent from1979 to 2024 is 39,800 square kilometers (15,400 square miles) per year, or 2.5 percent per decade relative to the 1981 to 2010 average. Based on the linear trend values, the maximum extent has declined 1.79 million square kilometers (691,000 square miles) since 1979. This is equivalent to the size of Alaska or five times the size of Germany.

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

Rank Year In millions of square kilometers In millions of square miles Date
1 2017 14.41 5.56 March 7
2 2018 14.47 5.59 March 17
3 2016
2015
14.51
14.52
5.60
5.61
March 23
February 25
5 2023 14.62 5.64 March 6
6 2011
2006
14.67
14.68
5.66
5.67
March 9
March 12
8 2007
2021
14.77
14.78
5.70
5.71
March 12
March 12
10 2019 14.82 5.72 March 13

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

Leaping toward spring

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 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

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 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

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 December 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

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 | High-resolution image

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
High-resolution image

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 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 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

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 decreasesGeophysical 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.

Antarctic sea ice extent hits a third low in a row

On February 20, Antarctic sea ice likely reached its minimum extent of 1.99 million square kilometers (768,000 square miles), tying for second lowest extent in the 1979 to 2024 satellite record. This is the third consecutive year that Antarctic sea ice has reached a minimum below 2.0 million square miles (772,000 square miles).

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

Overview of conditions

Antarctic sea ice extent on February 20, 2024

Figure 1. Antarctic sea ice extent for February 20, 2024, was 1.99 million square kilometers (768,000 square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On February 20, 2024, sea ice surrounding Antarctica reached an annual minimum extent of 1.99 million square kilometers (768,000 square miles), tying for second lowest minimum with 2022 in the 46-year satellite record. This year’s minimum is 850,000 square kilometers (328,000 square miles) below the 1981 to 2010 average Antarctic minimum extent of 2.84 millions square kilometers (1.10 million square miles). It is also 200,000 square kilometers (77,000 square miles) above the previous record low set on February 21, 2023. Nearly all of the remaining sea ice is in the Weddell Sea, Amundsen Sea, and the Southern Ocean off of Victoria Land, with isolated patches along the coasts of Enderby Land and Wilkes Land.

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

Conditions in context

Antarctic sea ice extent on February 20, 2024, compared with other years

Figure 2a. The graph above shows Antarctic sea ice extent as of February 20, 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 2013 to 2014 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

trend of antarctic sea ice loss from 1979 to 2024

Figure 2b. This graph shows Antarctic annual sea ice minimum extent, depicted as black diamonds, from 1979 to 2024, based on a 5-day running average of daily extent. The linear trend line is in blue with a 1.7 percent per decade downward trend, which is not statistically significant. A five-year running average is shown in red.

Credit: W. Meier, NSIDC
High-resolution image

This year marks the third consecutive minimum Antarctic sea ice extent below 2.0 million square kilometers (772,000 square miles) (Figure 2a). The three minimums set in 2022, 2023, and 2024 are the three lowest in the 46-year record. Five of the lowest Antarctic sea ice extents have occurred since 2017 (see table below). With this series of low years, the trend in Antarctic minimum extent is negative and it is natural to speculate if this decline is significant. However, the period since 2017 is still too short to assess if these recent low extents indicate a clear decreasing signal; the magnitude of the trend is still small relative to the year-to-year variations in the ice cover. Note in this respect that 2013 through 2015 saw near record high minimum extents.

Overall, the downward trend in the annual Antarctic sea ice minimum extent computed over the complete satellite record is 4,700 square kilometers (1,800 square miles) per year, or 1.7 percent per decade relative to the 1981 to 2010 average. This trend is not statistically significant (Figure 2b). This is in stark contrast to the Arctic where the trend in the sea ice minimum is larger in magnitude and has strong statistical significance.

Five lowest minimum Antarctic sea ice extents (satellite record, 1979 to present)

Table 1. Five lowest minimum Antarctic sea ice extents (satellite record, 1979 to present)
RANK YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN SQUARE MILES
1 2023 1.79 691,000 Feb. 21
2 2022
2024
1.98
1.99
764,000
768,000
Feb. 25
Feb. 20
4 2017 2.11 815,000 Mar. 3
5 2018 2.22 857,000 Feb. 21

Values within 40,000 square kilometers (15,000 square miles) are considered tied. 

For more information

NASA visualization of 2024 Antarctic sea ice minimum extent
NASA video of 2024 Antarctic sea ice minimum extent

Nothing Swift about January’s Arctic sea ice

Arctic sea ice growth was slower than average through most of the month, but with extent slightly declining towards the end of the month. Antarctic sea ice extent returned to near-record daily lows after a brief excursion out of the lowest five years.

Overview of conditions

Figure 1. Arctic sea ice extent for XXXX 20XX was X.XX million square kilometers (X.XX 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 1a. Arctic sea ice extent for January 2024 was 13.92 million square kilometers (5.37 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 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years and the record low year. 2022 to 2023 is shown in blue, 2021 to 2022 in green, 2020 to 2021 in orange, 2019 to 2020 in brown, 2018 to 2019 in magenta, and 2011 to 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1b. The graph above shows Arctic sea ice extent as of February 4, 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

The year 2024 began with an average January Arctic sea ice extent of 13.92 million square kilometers (5.37 million square miles), the twentieth lowest in the 45-year satellite record (Figure 1a). During the month, extent increased by 1.09 million square kilometers (421,000 square miles), which was slower than the 1981 to 2010 average increase of 1.33 million square kilometers (514,000 square miles) (Figure 1b). Extent actually declined for a few days at the end of the month. During the growth season, such short-term declines are not unusual at this time of year and are caused by weather systems that temporarily halt ice growth or push the ice northwards.

Extent was low in the Barents Sea with open water extending offshore of the northwest tip of Novaya Zemlya, as well as in the Gulf of St. Lawrence. Elsewhere, extent was near average.

Conditions in context

Arctic air temperature for January 2024 as difference from long-term average

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for January 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

Average sea level pressure for Arctic for Jan 2024

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for January 2024. 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

Overall, it was relatively warm over the Arctic Ocean during January (Figure 2a). Air temperatures at the 925 millibar level (about 2,500 feet above sea level) were up to 6 degrees Celsius (11 degrees Fahrenheit) above average over the central Arctic Ocean and the Canadian Archipelago. Air temperatures in the Bering Sea were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above average. It was slightly cooler than average over the East Siberian Sea.

The sea level pressure pattern was characterized by low pressure over the Barents and Bering Seas and a saddle of relatively high pressure extending from Eastern Siberia across the Arctic Ocean into northwestern Canada (Figure 2b). Overall, pressure gradients were not particularly strong, indicating slack winds.

January 2024 compared to previous years

linear decline of sea ice in Arctic 1979 to 2024

Figure 3. Monthly January ice extent for 1979 to 2024 shows a decline of 2.8 percent per decade.

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

The downward linear trend in Arctic sea ice extent for January over the 45-year satellite record is 41,000 square kilometers (16,000 square miles) per year, or 2.8 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, January has lost 1.73 million square kilometers (668,000 square miles) of ice since 1979. This is equivalent to the 2.5 times the size of state of Alaska or the country of Iran. However, the relatively high ice extent for January 2024 is notable.

Arctic sea ice thickness update

map of sea ice thickness as of December 15, 2023

Figure 4a. This map of the Arctic shows average sea ice thickness in meters on December 15, 2023. Warmer colors indicate thicker ice; cooler colors indicate thinner ice. The European Space Agency’s (ESA’s) Soil Moisture Ocean Salinity (SMOS) and CryoSat-2 satellites help determine average sea ice thickness.

Credit: Images from ESA SMOS & CryoSat-2 Sea Ice Data Product Processing and Dissemination Service, provided by Stefan Hendricks, Alfred Wegener Institute
High-resolution image

map of Arctic sea ice thickness as of December 15, 2023

Figure 4b. This map of the Arctic shows sea ice thickness as a difference from the 2011 to 2023 average on December 15, 2023. The European Space Agency’s (ESA’s) Soil Moisture Ocean Salinity (SMOS) and CryoSat-2 satellites help determine average sea ice thickness.

Credit: Images from ESA SMOS & CryoSat-2 Sea Ice Data Product Processing and Dissemination Service, provided by Stefan Hendricks, Alfred Wegener Institute
High-resolution image

Sea ice thickness can be estimated from satellite-borne altimeters. Currently, two altimeters are providing thickness estimates over the Arctic Ocean. One is the NASA Ice, Cloud, Land elevation Satellite 2 (ICESat-2), a laser altimeter; ICESat-2 data products are archived at the NASA Snow and Ice Distributed Active Archive Center (DAAC) at NSIDC. The other is the European Space Agency’s (ESA’s) CryoSat-2, a radar altimeter. In combination with estimates for thin regions from the ESA Soil Moisture Ocean Salinity (SMOS) satellite, CryoSat-2 provides daily updated weekly average thickness (Figure 4a).

As Arctic sea ice extent starts approaching its maximum, ice thickness can provide an indication of the state of the ice cover. The most recent (mid-December 2023) thickness analysis from the ESA SMOS & CryoSat-2 Sea Ice Data Product Processing and Dissemination Service at Alfred Wegener Institute indicates up to 1.25 meters (4.1 feet) thicker ice than the 2011to 2023 average over the Siberian side of the Arctic, with ice on the North American side up to 1.25 meters (4.1 feet) thinner than average (Figure 4b). This suggests that there may be a slower melt out of ice in the Siberian coastal seas, but perhaps faster in the Beaufort Sea.

Antarctic sea ice

Sea ice extent for Antarctica for January 2024

Figure 5. Antarctic sea ice extent for January 2024 was 3.96 million square kilometers (1.53 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

Sea ice extent in the Antarctic started the year at 6.37 million square kilometers (2.46 million square miles), or sixth lowest in the satellite record for January 1. As the melt season continued in the Southern Hemisphere, a rapid decline in daily extent led to it ending the month at 2.58 million square kilometers (996,000 square miles), tying for second lowest with 2017 for that date. Antarctic sea ice extent for January overall averaged 3.96 million square kilometers (1.53 million square miles), tying for fourth lowest extent with 2022. Extent was particularly low in the Ross, Bellingshausen, and Amundsen Seas, but has been near average in the Weddell Sea. Little ice remains in the East Antarctic sectors.

A team from the University of Colorado and the Instituto Argentino Antartico are en route to the Antarctic Peninsula and the Larsen B embayment. This region’s glaciers have become more active again after an area of multiyear fast ice broke away in 2022.

 

Fast December expansion

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 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

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 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

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

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. ||Credit: Zachary Labe, Princeton University| High-resolution image

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
High-resolution image

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 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 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

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

A brief winter pause

While autumn sea ice growth is in full swing, brief pauses are not unusual. Starting November 22, the ice growth stalled almost completely for five days as a series of storms guided an atmospheric river into the Arctic, transporting warm, moist air.

Overview of conditions

Arctic sea ice extent for November 2023

Figure 1a. Arctic sea ice extent for November 2023 was 9.66 million square kilometers (3.73 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for 2023 and other years

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

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

Arctic sea ice extent for November 2023 averaged 9.66 million square kilometers (3.73 million square miles), tying with 2006 for seventh lowest in the 45-year satellite record (Figure 1a). Overall, during November, sea ice extent increased by 70,800 thousand square kilometers (27,300 square miles) per day, slightly faster than the 1981 to 2010 average of 69,500 square kilometers (26,800 square miles) per day (Figure 1b). Freeze up temporarily stalled starting November 22, as several cyclones brought warm, moist air into the north Atlantic. The strong winds helped to push the ice edge in the East Greenland and Barents Seas northwards, limiting new ice formation. A cyclone in the Bering Sea around this time also pushed the ice edge polewards in the Chukchi Sea. Ice growth for November occurred all along the margins of the Arctic Ocean, dominated by growth in Baffin Bay and the southern Beaufort Sea.

A November pause in ice growth occurred three times in the past: November 3 to 8, 2013; November 13 to 20, 2016; and now November 19 to 24, 2023. Thus, such events are rare but not unknown.

Conditions in context

Air temperature as a difference from average for Arctic in November 2023

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for November 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

average sea level pressure in the Arctic for November 2023

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for November 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 over the Arctic Ocean at the 925 millibar level (about 2,500 feet above the surface) in November were broadly similar to those seen in October, with mostly above average warmth in and around the Canadian Archipelago of 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) (Figure 2a). Temperatures were modestly above average north of Greenland and stretching towards the Laptev and Kara Seas as well as the southern parts of the Beaufort Sea. The East Siberian Sea experienced near- to slightly-below average temperatures; temperatures were slightly below average over the Barents and Norwegian Seas.

The atmospheric circulation for November featured fairly strong low pressure centered near the North Pole, with strong low pressure also dominating the north Atlantic, Eurasia, Baffin Bay, and North America (Figure 2b).

November 2023 compared to previous years

trend of Arctic sea ice decline from 1979 to 2023 for November

Figure 3. Monthly November ice extent for 1979 to 2023 shows a decline of 4.7 percent per decade.

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

The downward linear trend in Arctic sea ice extent for November over the 45-year satellite record is 50,600 square kilometers (19,500 square miles) per year, or 4.7 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, November has lost 2.28 million square kilometers (880,000 square miles) of ice since 1979. This is 1.3 times the size of Alaska.

Rivers in the sky slow winter ice growth

Map of atmospheric river forming in Arctic at end of November

Figure 4a. This image from Climate Reanalyzer shows precipitable water (column water vapor) on November 26, 2023, from the National Oceanic and Atmospheric Administration (NOAA) Global Forecast System (GFS) model. While the Arctic atmosphere tends to be quite dry, an atmospheric river of high water vapor content (beige colors indicating 10 to 20 kilograms per square meter) is visible along the east coast of Greenland and over Svalbard to the north.

Credit: Climate Reanalyzer
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Wind speed and direction in Arctic on November 26, 2023

Figure 4b. This image from Climate Reanalyzer shows wind speed at 10 meters above the surface on November 26, 2023, from the National Oceanic and Atmospheric Administration (NOAA) Global Forecast System (GFS) model. Higher winds speeds (blue and green shades, 15 to 30 knots), which are from the south, are seen in the same area as the atmospheric river of high water vapor content extending into the Arctic Ocean.

Credit: Climate Reanalyzer
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From November 21 to 28, a series of three extratropical cyclones followed a common track from the northeast coast of Greenland eastward along the northern edge of the Barents, Kara, and Laptev Seas. As each storm moved into the Arctic Ocean, it merged with its predecessors, creating a persistent cyclonic (counter clockwise) wind regime. The first and third of these storms originated in the Icelandic Low region before migrating up the east side of Greenland. The second storm originated just north of Greenland. Simultaneously, a center of high pressure developed over the ice-free part of the Barents Sea, becoming especially strong on November 26 to 28.

This combination of persistent low pressure to the north and west of Svalbard and a high-pressure center to the southeast created a strong, persistent flow from the south of relatively warm and moist air from the North Atlantic Ocean toward Svalbard, which then turned eastward along the marginal ice zone. This is seen as an extension of an atmospheric river into the Arctic. Atmospheric rivers are long narrow corridors that carry a large amount of water vapor. A recent study suggests that atmospheric rivers lead to ice loss by transporting warm, moist air into the Arctic that can limit sea ice growth. This is consistent with the observed pause in seasonal ice growth in late November.

A wetter and warmer Arctic

 Autumn (September, October, November [SON]) trends for sea ice concentration (SIC) (top row), surface air temperature (middle row), and specific humidity (bottom row). Column (a) shows the trends over the full 20-year period (2003-2022) of the AIRS instrument analyzed by Boisvert et al. (2023). Column (b) shows the trends over the first half of the record (2003-2012), and Column (c) shows the trends over the second half of the record (2013-2022). Image from Boisvert et al. (2023).

Figure 5. The top row of maps shows trends for surface air temperature during Autumn (September, October, November [SON]), and the bottom row shows specific humidity during the same period. Column (a) shows the trends over the full 20-year period from 2003 to 2022 of the Atmospheric Infrared Sounder (AIRS) instrument analyzed by Boisvert et al. 2023. Column (b) shows the trends over the first half of the record from 2003 to 2012, and Column (c) shows the trends over the second half of the record from 2013 to 2022.

Credit: Boisvert et al. 2023
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The Atmospheric Infrared Sounder (AIRS) instrument on board NASA’s 21-year-old Aqua satellite has been taking twice-daily global measurements of the Earth’s temperature and humidity. When looking at these variables in the Arctic between 2003 to 2022, it was found that specifically in the fall months (September, October, November; SON) the near-surface air temperature and specific humidity has increased by 1.78 Kelvin and 0.26 grams of water vapor per kilogram of air since 2003 (column A). This warming and moistening is widespread over the Arctic Ocean and most pronounced in areas of sea ice loss. However, during the first 10 years of this record (column B) the sea ice loss was roughly three times as large as in the most recent 10 years (column C). The rapid loss of sea ice coverage in the first decade helped temperatures to rise more than 3.5 times the rate compared to the last decade. In the first decade the warming and moistening was widespread over the Arctic Ocean; however, in the most recent decade, this warming and moistening is more tightly coupled with smaller areas of sea ice loss. So, although the Arctic is becoming warmer with higher humidity over the past 20 years, these trends were driven by the rapid loss of sea ice coverage during the first 10 years of this record.

Antarctic sea ice: race to the bottom

Antarctic sea ice extent for 2023 and 2016

Figure 6a. The graph above shows Antarctic sea ice extent as of December 4, 2023, along with daily ice extent data for 2016 and 2022, the second lowest year. 2016 is shown in dark gray, 2022 in dashed red, and 2023 in blue. 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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Air temperatures over Antarctica as a difference from average for November 2023

Figure 6b. This plot shows the departure from average air temperature in Antarctica at the 925 hPa level, in degrees Celsius, for November 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
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The decline in Antarctic sea ice extent paused for a few days around November 9, which caused it to surpass the daily extents for November 2016 for most of the month, making it the second-lowest extent in the 45-year record. This was the first time that the 2023 extent was not the lowest in the record for each day since early May. However, the seasonal decline then picked up and closely followed the path of the record low 2016 daily extents, remaining slightly above but close to the 2016 daily values (Figure 6a). At month’s end, ice extent remained persistently low in the Weddell, Cosmonaut, and Ross Seas, but above the 1981 to 2010 average in the Bellingshausen and Amundsen Seas. Unusually warm conditions over the eastern Weddell Sea and strong offshore winds just to the east (Dronning Maud Land coast) caused retreat of ice along that coast and opened a wide shore polynya in that area (Figure 6b).

Further reading

Boisvert, L., C. Parker, and E. Valkonen. 2023. A warmer and wetter Arctic: Insights from a 20-years AIRS record. Journal of Geophysical Research: Atmospheres, 128, e2023JD038793. doi:10.1029/2023JD038793.

Fritts, R. 2023. Rivers in the sky are hindering winter Arctic sea ice recovery. Eos,104,13 March 2023. doi:10.1029/2023EO230098.

Zhang, P., G. Chen, M. Ting, and et al. 2023. More frequent atmospheric rivers slow the seasonal recovery of Arctic sea ice. Nature Climate Change, 13, 266–273. doi:10.1038/s41558-023-01599-3.

The long Arctic winter sets in

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 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

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
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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 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 the departure from 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

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
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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

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

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.

The Sun sets on the Arctic melt season

A few days after the annual Arctic sea ice minimum extent was reached on September 19, the sun set at the North Pole, aiding sea ice growth. Arctic sea ice extent has grown at a fairly slow pace, leading to the fifth lowest September in the 45-year passive microwave satellite record. Antarctic sea ice extent has had an uptick in growth, but remains at record low levels for this time of year.

Overview of conditions

September sea ice extent in Arctic

Figure 1a. Arctic sea ice extent for September 2023 was 4.37 million square kilometers (1.69 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for 2023 and other years

Figure 1b. The graph above shows Arctic sea ice extent as of October 3, 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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sea ice concentration in Arctic on October 2, 2023

Figure 1c. This image from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2) shows sea ice concentration in the Arctic Ocean on October 2, 2023, highlighting the openings of sea ice north of Alaska within the Beaufort and Chukchi Seas.

Credit: Japan Aerospace Exploration Agency, courtesy University of Bremen
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Average Arctic sea ice extent for September 2023 was 4.37 million square kilometers (1.69 million square miles), placing it fifth lowest in the 45-year satellite record (Figure 1a). Following the annual minimum of 4.23 million square miles (1.63 million square kilometers), the growth in Arctic sea ice extent has been slower than average (Figure 1b). The image plot for October 2 from the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument provided by the University of Bremen shows that with the cessation of melt, the ice edge has become more sharply defined (Figure 1c). The lack of ice in the longitudes spanning the Laptev Sea eastward to the Beaufort Sea is striking; before ice forms in these areas the upper ocean will have to lose its remaining heat through radiation and convective transfer to the atmosphere and space. The Northern Sea Route remains essentially free of ice. While both the Northern (deepwater) and Southern (Amundsen’s) routes of the Northwest Passage appear largely ice free, some ice still remains in the northern route, notably at the eastern entrance of M’Clure Strait. This is discussed further below.

Conditions in context

Air temp anomaly September 2023 for Arctic

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for September 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
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Average air pressure for September in Arctic

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars for September 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 (approximately 2,500 feet above the surface) for September were modestly above average, with temperatures 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) over most of the Arctic Ocean (Figure 2a). Warm conditions prevailed in the ice-free Norwegian, Barents, and Kara Seas. Over land, Canada and northwestern Eurasia experienced warm conditions, as much at 5 degrees Celsius (9 degrees Fahrenheit) above average.

The atmospheric circulation for September was characterized by fairly low pressure over most of the Arctic Ocean, notably north of the Barents and Laptev Seas and east of Greenland (Figure 2b). Over land, high pressure prevailed over Eurasia and eastern Canada.

September 2023 compared to other years

decline trend line of sea ice in Arctic

Figure 3. Monthly September ice extent for 1979 to 2023 shows a decline of 12.2 percent per decade.

Credit: National Snow and Ice Data Center
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The downward linear trend in Arctic sea ice extent for September over the 45-year satellite record is 78,500 square kilometers (20,300 square miles) per year, or 12.2 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, September has lost 3.45 million square kilometers (1.33 million square miles) of ice. This is roughly equivalent to twice the size of Alaska or Iran.

The Northern Hemisphere’s summer 2023 in review

Air temperature anomaly April to August in Arctic

Figure 4a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, from April to August 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
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Map and chart of sea ice age in Arctic from 1979 to 2023

Figure 4b. The top maps show Arctic sea ice age at the end of summer, a week before the seasonal minimum, for 1985 on the left and 2023 on the right. The bottom time series shows extent of multiyear ice in black and ice >4 years old in red at the seasonal minimum for 1985 to 2023. The oldest (4+ year old) ice is in red.

Credit: Data and images from Tschudi et al., 2019a and 2019b
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With the passing of the seasonal maximum in Arctic sea ice extent on March 6, the melt season started slowly, but daily extents remained among the third to sixth lowest in the satellite record. The pattern of slow ice loss persisted through April—average extent for April ranked tied with 2002 as tenth lowest in the satellite record. The rate of ice loss picked up towards the end of May, dropping extent below the interdecile range after spending most of the month just above the lower part of the inter-decile range. Nevertheless, extent for the month as a whole ranked only thirteenth lowest in the satellite record. June sea ice loss proceeded at only an average rate and by month’s end, it was clear that a record low September ice extent was highly unlikely. While the rate of Ice loss picked up in August, the sea ice minimum reached on September 19 ended up as sixth lowest in the satellite record. The April through August average air temperate map at the 925 hPa level tells the basic story of 2023—temperatures were below average over much of the Arctic Ocean, limiting melt (Figure 4a). The year nevertheless ended up as notable for the combination of ice-fee conditions in the southern (Amundsen’s) Northwest Passage route and very mild ice conditions in the northern (deepwater) route; this is consistent with the above average temperatures at the 925 hPa level over the Canadian Arctic Archipelago.

Multiyear ice extent at the end of summer was quite low, as has been the case for the last several years (Figure 4b). A band of multiyear ice persists on the Atlantic side, extending from the Laptev Sea across the Arctic north of the Kara and Barents Seas. Much of this ice will likely drift out of the Arctic Ocean with the Transpolar Drift Stream over the next several months to a year. Very little of the oldest (4+ years old) ice remains in the Arctic, with small patches north of Greenland and an area north of the Beaufort Sea. The total extent of the oldest sea ice is 93,000 square kilometers (36,000 square miles), the second lowest in the satellite record since 1985, only higher than 55,000 square kilometers (21,000 square miles) in 2019. This is in stark contrast to the 1980s when old ice covered over 2.5 million square kilometers (965,000 square miles) of the Arctic Ocean.

Note that operational ice services track sea ice daily primarily for the safety of on-ice operations and ships at sea. These services use data sources that go beyond the single source used here. For example, analysts at the US National Ice Center (USNIC) depend on radar and visible-band data when mapping Arctic ice. USNIC tracks Arctic-wide sea ice extent using charts they produce. NSIDC archives these charts. Currently, the USNIC analysis indicates a minimum of 5.05 million square kilometers (1.95 million square miles) on September 27. The USNIC extent values differ from the Sea Ice Index values used by ASINA because of the different imagery and analysis techniques employed.

The Southern Hemisphere’s winter 2023 in review

Antarctic sea ice extent for 2023 and other years

Figure 5a. The graph above shows Antarctic sea ice extent as of October 3, 2023, along with daily ice extent data for four previous years and 2014, the record maximum 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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animation showing sea ice extent shifting in Antarctic from 1979 to 2023

Figure 5b. Click on image to begin the animation. From 2013 through 2023, Antarctic sea ice exhibited its highest and lowest extents in the satellite record dating back to 1979. From 2013 through 2015, extents were mostly above the 1981 to 2010 average, including the record-high 2014 winter maximum. Beginning in 2016, extents were mostly below the 1981 to 2010 average. Antarctic sea ice extent fell to the lowest minimum on record in March 2023 and the lowest maximum in September 2023.

Credit: Animation by Michon Scott, based on NSIDC’s Charctic Interactive Sea Ice Graph
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Image of Nimbus data quality for 1966

Figure 5c. This image show the sea ice edge for the last week of August 1966 using the minimum Advanced Vidicon Camera System on the NASA Nimbus satellite. Superimposed is the sea ice edge, depicted as a black line, from the manual analysis.

Credit: Gallagher et al. 2014
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Average sea ice extent based on reconstruction and satellite data from 1905 to 2023

Figure 5d. This graph shows the average Antarctic extent for June through August for multiple decades. The blue line depicts the “best fit” from 1905 to 2020; the grey line depicts the upper and lower 95 percent range for the same time period; and the red line depicts the modern satellite data from the Sea Ice Index from 1979 to 2023. The Nimbus-II 1966 value is marked as a gold diamond within the uncertainty range, which is drawn as vertical gold line.

Credit: W. Meier, NSIDC
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The story for the southern hemisphere was very different. After a record low minimum extent in February 2023, the seasonal increase in ice extent was near average through March, but then began to slow in April (Figure 5a). By May, it became clear that Antarctic sea ice extent, while of course growing in response to seasonal cooling, was lagging far below previous daily lows in the satellite record. Extent was particularly low in the Bellingshausen Sea, Weddell Sea, and western Ross Sea regions. By the middle of July, the heart of austral winter, extent stood at more than 2.60 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. August saw particularly low extent in the Ross Sea and eastern Weddell Sea sectors, but with some recovery in the Bellingshausen Sea. On September 10, 2023, Antarctic extent reached an annual maximum of 16.96 million square kilometers (6.55 million square miles). This year’s maximum was 1.03 million square kilometers (398,000 square miles) below the previous record low set in 1986. There is growing evidence that the Antarctic sea ice system has entered a new regime, featuring a much stronger influence of warm ocean waters limiting ice growth (Figure 5b).

Average Antarctic sea ice extent for September was 16.80 million square kilometers (6.49 million square miles), also far below the previous record for the month. Average September sea ice extent was 1.69 million square kilometers (653,000 square miles) below the 1981 to 2010 average extent of 18.49 million square kilometers (7.14 million square miles). More remarkably, it was 880,000 million square kilometers (340,000 square miles) below 1986, the previous lowest September.

The extents this year have been far outside anything observed in the 45-year modern satellite record that began in 1979. However, some earlier satellite data, including that from the Nimbus satellites in the mid-1960s, point to extents that may rival 2023. Estimates derived from Nimbus-II data suggest that extent for 1966 may have been only slightly higher than 2023 (Gallaher et al., 2014). However, Nimbus-II carried only a visible sensor, which could not collect data during cloudy conditions, resulting in sparse coverage of the Antarctic sea ice region (Figure 5c).

Data was not collected for September when the maximum generally occurs, but only for May through August. In addition, the data quality was limited, making discrimination between ice and ocean difficult. It seems clear that while the 1966 May, June, and July estimates are on par with the 1979 to 2022 values, August 1966 was an outlier with lower extent than July 1966. This is not reasonable given the seasonality of the ice cover. The recovery of such old satellite data is valuable for providing long-term context; however, as just discussed data quality issues preclude making quantitative comparisons with the modern satellite record.

As discussed in the August 2 post, another source of pre-1979 data was recently published at NSIDC (Fogt et al., 2023). It is based on the reconstruction of sea ice extent from climate indices, atmospheric reanalyses, and other information (Fogt et al., 2022). A reconstruction approach uses relationships between observed sea ice extent from satellites and the collection of climate indices to derive a relationship between the two. This relationship is then extrapolated to the pre-satellite period. The reconstruction data set encompasses 1905 to 2020 as seasonal 3-month averages. Comparing the June to August average from that product with the satellite data indicates that this year is well outside average ranges of the 115-year reconstruction (Figure 5d). Like the Nimbus-II data, such reconstructions also have high uncertainty and depend on the assumption that the relationships between satellite data and climate indices are valid over the pre-satellite period.

Sea ice conditions in the Northwest Passage routes during the 2023

Annual extent of sea ice in Northern route of Northwest Passage for several years and 2023

Figure 6a. This time series shows total sea ice area for 2023, 2022, 2021, 2029, 2011, and the 1991 to 2020 average within the northern route of the Northwest Passage. Data are from the Canadian Ice Service.

Credit: S. Howell, Environment and Climate Change Canada
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Sea ice concentration in Northwest Passage for week of September 25, 2023

Figure 6b. These maps show sea ice concentration in the Northwest Passage for the week of September 25, 2023. The left map shows spatial distribution of total sea ice concentration; the middle map shows the 1991 to 2020 average sea ice concentration for the same week; and the map on the right shows the difference in sea ice concentrations between the 1991 to 2020 average and the week of September 25, 2023. Red shows a stark decline from the average. Data are from the Canadian Ice Service.

Credit: S. Howell, Environment and Climate Change Canada
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Chart showing extent in southern sea route of Northwest Passage for several years and 2023

Figure 6c. The time series shows total sea ice area for 2023, 2022, 2021, 2029, 2011, and the 1991 and 2020 average within the southern route of the Northwest Passage. Data are from the Canadian Ice Service.

Credit: S. Howell, Environment and Climate Change Canada
High-resolution image

Our colleague Steve Howell at Environment and Climate Change Canada (ECCC) has provided an up-to-date summary of sea ice conditions in the Northwest Passage based on ice charts created by the Canadian Ice Service. While ice conditions at the end of the 2023 melt season were certainly remarkable, the northern route of Northwest Passage route did not break record low conditions of 2011, but still ranks second lowest since 1968 and is well below the 1991 to 2020 average (Figure 6a). Preliminary analysis indicates that the atmospheric circulation over the Canadian Arctic Archipelago during August and September of 2023 was not favorable to Arctic Ocean ice advection, which typically prevents the northern route from clearing. Interestingly, sea ice extent on September 25 is lower than in 2011 during the same time period (Figure 6b). Although the northern route was virtually sea ice free, complete transit without icebreaker escort would be difficult because of sea ice blocking the opening at M’Clure Strait. By contrast, the southern route is sea ice free from end to end (Figure 6c).

Further reading

Fogt, R. L., A. M. Sleinkofer, M. N. Raphael, H. S. and Handcock. 2022. A regime shift in seasonal total Antarctic sea ice extent in the twentieth centuryNature Climate Change 12, 54– 62, doi:10.1038/s41558-021-01254-9.

Fogt, R., M. N. Raphael, and M. S. Handcock. 2023. Seasonal Antarctic Sea Ice Extent Reconstructions, 1905-2020, Version 1 [Data Set]. Boulder, Colorado USA. National Snow and Ice Data Center, doi:10.7265/55×7-we68. Date Accessed 09-28-2023.

Gallaher, D., G. G. Campbell, W. N. Meier. 2014. Anomalous variability in Antarctic sea ice extents during the 1960s with the use of Nimbus data. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 3(7), 881-887, doi:10.1109/JSTARS.2013.2264391.

Tschudi, M., W. N. Meier, J. S. Stewart, C. Fowler, and J. Maslanik. 2019a. EASE-Grid Sea Ice Age, Version 4 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/UTAV7490FEPB. Date Accessed 10-02-2023.

Tschudi, M., W. N. Meier, and J. S. Stewart. 2019b. Quicklook Arctic Weekly EASE-Grid Sea Ice Age, Version 1 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/2XXGZY3DUGNQ. Date Accessed 10-02-2023.