For the second consecutive year, winter sea ice in the Arctic reached a level that matches the lowest peak observed since satellite monitoring began in 1979. On March 15, Arctic sea ice extent reached 5.52 million square miles (14.29 million square kilometers), very close to the 2025 peak of 5.53 million square miles (14.31 million square kilometers). Scientists with NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder, note that the two years are statistically tied.
Along with the overall extent, researchers are also observing changes in ice thickness. "Based on what we're seeing with NASA's ICESat-2 satellite, much of the ice in the Arctic is thinner this year, especially in the Barents Sea northeast of Greenland.," said Nathan Kurtz, chief of the Cryospheric Sciences Laboratory at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The Sea of Okhotsk that borders northern Japan and Russia also had relatively low ice this year - a region that naturally experiences significant year-to-year variability."
Scientists with NASA and NSIDC found that this winter's peak Arctic ice coverage continues the long-term trend observed over the past several decades. This year, peak ice cover was below the average levels between 1981 and 2010 by roughly half a million square miles (about 1.3 million square kilometers).
Sea ice extent is defined as the total area of the ocean with at least 15% ice concentration. The area of the Arctic Ocean covered in ice expands in the cold of winter. Although much of the sea ice melts in warmer months, some ice remains throughout the year. Recently, less new ice has been forming. As a result, less multi-year ice has accumulated.
"A low year or two don't necessarily mean much by themselves," said NSIDC ice scientist Walt Meier. But viewed within the long‑term downward trend since 1979, Meier added, they add to the overall picture of change in Arctic sea ice throughout the seasons.
In the Antarctic, summer sea ice reached an annual low of 996,000 square miles (2.58 million square kilometers) on Feb. 26. This year's coverage represents an increase compared to the unusually low levels of the past four years. Although 100,000 square miles (260,000 square kilometers) lower than the 1981-2010 average, the Antarctic sea ice minimum was well above the record low set on Feb. 21, 2023, of 691,000 square miles (1.79 million square kilometers).
Scientists at NSIDC previously tracked sea ice extent primarily using satellites in the Defense Meteorological Satellite Program. In recent years, the NSIDC has relied on JAXA's (Japan Aerospace Exploration Agency) Advanced Microwave Scanning Radiometer 2 for real-time sea ice data. Researchers also compare ice coverage to historical sources, such as the data collected between 1978 and 1985 with the Nimbus-7 satellite that was jointly operated by NASA and the National Oceanic and Atmospheric Administration.
