A map shows the Arctic Ocean topped with white, which represents sea ice at the time of its annual maximum extent. Most of the sea ice is well within a yellow line that indicates the much larger 1981-2010 median extent for the month of March.
Winter sea ice cover in the Arctic was the lowest it’s ever been at its annual peak on March 22, 2025, according to NASA and the National Snow and Ice Data Center (NSIDC). At 14.33 million square kilometers (5.53 million square miles), the maximum extent fell below the prior low of 14.41 million square kilometers (5.56 million square miles) in 2017.
In the dark and cold of winter, sea ice forms and spreads across Arctic seas. But in recent years, less new ice has been forming, and less multi-year ice has accumulated. This winter continued a downward trend scientists have observed over the past several decades.
The map above shows the ice extent on March 22, the day of the 2025 maximum. To determine extent, scientists project satellite observations of sea ice onto a grid and then add up the total area of each cell that is at least 15 percent ice-covered. The yellow outline shows the median sea ice extent for March (1981-2010), the month when the ice generally reaches its maximum extent. A median is the middle value; that is, half of the extents were larger than the yellow line and half were smaller.
A thick red line charts the 2025 Arctic sea ice extent from January through most of March. At its highest point, the red line on March 22 is well below average, shown as a blue dotted line, and below the previous lowest maximum of 2017, shown as a dashed orange line.
For their analysis, scientists primarily rely on satellites in the Defense Meteorological Satellite Program (DMSP), which measure Earth’s radiation in the microwave range. The DMSP data are augmented with historical sources, including data collected between 1978 and 1985 with the Nimbus-7 satellite that was jointly operated by NASA and the National Oceanic and Atmospheric Administration.
At the sub-Arctic level, many parts of the region saw sea ice extents well below the 1981-2010 average this winter. For instance, low ice prevailed across the Gulf of St. Lawrence, likely influenced by warm air and ocean surface temperatures, for most of the season. Onshore winds, which can prevent new ice formation, may have also contributed.
“We’re going to come into this next summer season with less ice to begin with,” said Linette Boisvert, an ice scientist at NASA’s Goddard Space Flight Center. “It doesn’t bode well for the future.”
NASA Earth Observatory images by Lauren Dauphin, using data from the National Snow and Ice Data Center. Story by James R. Riordon/NASA’s Earth Science News Team, adapted for Earth Observatory by Kathryn Hansen.