Arctic sea ice extent in May declined at a slightly faster pace compared to average. In Antarctica, the Bellingshausen Sea remains nearly ice free as far south as 72 degrees South by the end of May.
The Sea Ice Today team is working on solutions to the recent gaps in satellite swath data, as well as preparing for an upcoming need to transition to another satellite sensor. The team uses the standard five-day trailing mean and other gap-filling techniques that ensure continued tracking of polar sea ice when data gaps exist.
Overview of conditions
May sea ice extent in the Arctic averaged 12.56 million square kilometers (4.85 million square miles), tying with 2004 for seventh lowest on the 47-year satellite record (Figure 1a). Arctic sea ice extent is 640,000 square kilometers (247,000 square miles) above the record low May ice extent set in 2016. Ice loss in May primarily occurred within the Barents Sea, as well as in the Bering Sea and the Sea of Okhotsk (Figure 1b). The North Water Polynya in northern Baffin Bay extended further south through the month. Overall, the sea ice extent at the end of the month was particularly low in the Barents Sea and Bering Sea.
Figure 1a. The graph above shows Arctic sea ice extent as of June 2, 2025, along with daily ice extent data for four previous years and the record low year. 2025 is shown in blue, 2024 in green, 2023 in orange, 2022 in brown, 2021 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.
Figure 1b. Arctic sea ice extent for May 2025 was 12.56 million square kilometers (4.85 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data
Conditions in context
NSIDC will be shifting to use atmospheric temperature and circulation data from either the NOAA's Climate Forecast System Reanalysis (CFSR) or the European Centre for Medium Range Forecasts ERA5 reanalysis. For this post, we are still using data from NOAA's National Centers for Environmental Prediction (NCEP) reanalysis for initial descriptions. CFSR and ERA5 data are available several days after the first of the month and will be added to this post when available.
Across the Arctic Ocean, slightly warm conditions were the general rule, with air temperatures at the 925 millibar level (about 2,500 feet above sea level) up to 1 degree Celsius (2 degrees Fahrenheit) above average (Figure 2a). Average temperatures prevailed over northern Norway and the Barents Sea, replacing cool conditions during the previous month. Near-average temperatures were also present between Greenland and Iceland in the Denmark Strait. However, slightly cool conditions prevailed over Greenland.
The month of May was dominated by a pronounced Beaufort High, characterized by anticyclonic conditions over the central Arctic Ocean paired with lower pressure centered over the Bering Sea and Gulf of Alaska (Figure 2b). This pattern drove cool conditions to northern Alaska and the Yukon, while a strong flow from the south led to warm conditions between Greenland and Svalbard in the Denmark Strait.
May 2025 compared to previous years
The downward linear trend in Arctic sea ice extent through 2025 for May is 30,600 square kilometers (11,800 square miles) per year or 2.3 percent per decade relative to the 1981 to 2010 average (Figure 3). Based on the linear trend, since 1979, May has lost 1.41 million square kilometers (544,000 square miles) of sea ice. This is equivalent to twice the size of Texas.
Satellite transition
As many viewers of our daily updates are aware of, delivery from our US Navy source for the passive microwave input data have become more erratic. Moreover, NSIDC has been informed that the Defense Department will reduce the priority of processing the SSMI/S data which, with its predecessors of SSM/I and SMMR, has been the mainstay of our reporting. This satellite series has provided consistent tracking of the sea ice conditions for 47 years. NSIDC will explore switching to a different sensor, the JAXA Advanced Microwave Scanning Radiometer 2 (AMSR2). Provided that our funding continues in this uncertain environment, we should be able to post our regular analyses after calibrating between sensors to keep the time series as consistent as possible.
Yes, Arctic sea ice took a turn in 2007
A recent study by our colleague Harry Stern confirms what previous studies (Babb et al. 2023 and Sumata et al. 2023) and NSIDC scientists have observed since 2007 regarding a shift in Arctic sea ice conditions. Stern's study uses a statistical method to show that the overall decline in Arctic September monthly sea ice extent, in the satellite monitoring era (1978 to present), can be described as a steady decline from 1978 to 2006 followed by a relatively flat but variable trend from 2007 onward (Figure 4).
Although much has been written about the extreme record low sea ice extent of September 2012, the greatest year-on-year drop was between September 2006 and 2007. The study attributes the change to the rapid loss of thicker multiyear ice in the central Arctic over the course of the 1990s and early 2000s. In 1980, much of the Arctic Ocean ice cover was filled with multiyear ice more than 4-years old, built up by preceding decades of cool (or, at the time, typical) summer seasons. But by the late 1990s, warmer summers resulted in extensive melting of this older ice, particularly along the southernmost part of the Beaufort Gyre, north of Alaska. Export of ice through Fram Strait gradually increased as well, as the proportion of thick old floes in the high Arctic decreased and the ice became more mobile. The summer of 2007 had a pronounced loss of older ice through both these processes, and within a few years of that event, only the North American side of the Beaufort Sea gyre retained significant older ice, and the tongue of older ice that moved westward to the Alaskan coast and Bering Strait area never survived the summer season.
Since 2007, Arctic sea ice has been in a roughly stable, reduced-ice state. Now, the annual formation of first-year ice dominates sea ice conditions with winter drift and compression of that ice, followed by extensive summer melting in the western Arctic and Eurasian coast. Very little ice more than 4-years old survives. A downward trend is expected to return as the Arctic keeps warming and its oceanography continues to change.
Antarctica's autumn growth missed a spot...actually, two
Antarctic sea ice extent for May was fifth lowest in the satellite record, but below average growth through the month resulted in the daily ice extent moving away from the 1981 to 2010 average. In particular, two regions are far behind in ice re-growth: the Bellingshausen Sea and eastern Dronning (Queen) Maud Land (Figure 5a). The rest of the ice pack had near or only slightly below the average extent. Amazingly, as June begins, the Bellingshausen Sea remains almost entirely ice free, with only small areas of sea ice cover in its most southern reaches (Figure 5b). Both areas experienced very warm conditions in May, and in the Bellingshausen Sea, temperatures that were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) above average were driven by an above-average Amundsen Sea Low centered near 120 degrees West along the Antarctic coast.
Figure 5a. Antarctic sea ice extent for June 1, 2025, was 10.47 million square kilometers (4.04 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
Figure 5b. This map shows extremely low sea ice concentration in the Bellingshausen Sea off the coast of the Antarctic Peninsula. Sea ice concentration is based on data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) data as of June 1, 2025. Yellows indicate sea ice concentration of 75 percent; dark purples indicate sea ice concentration of 100 percent. — Credit: University of Bremen
Further reading
Babb, D. G., R. J. Galley, S. Kirillov, J. C. Landy, S. E. L. Howell, J. C. Stroeve, et al. 2023. The stepwise reduction of multiyear sea ice area in the Arctic Ocean since 1980. Journal of Geophysical Research: Oceans, 128, e2023JC020157, doi:10.1029/2023JC020157.
Stern, H. L. 2025. Regime shift in Arctic Ocean sea‐ice extent. Geophysical Research Letters, 52(8), e2024GL114546, doi:10.1029/2024GL114546.
Sumata, H., L. de Steur, D. V. Divine, et al. 2023. Regime shift in Arctic Ocean sea ice thickness. Nature 615, 443–449, doi:10.1038/s41586-022-05686-x.