With the end of summer approaching in the Northern Hemisphere, the extent of sea ice in the Arctic shrank to its annual minimum on Sept. 10, according to NASA and the National Snow and Ice Data Center. The total sea ice coverage was tied with 2008 for the 10th-lowest on record at 1.78 million square miles (4.60 million square kilometers). In the Southern Hemisphere, where winter is ending, Antarctic ice is still accumulating but remains relatively low compared to ice levels recorded before 2016.
The areas of ice covering the oceans at the poles fluctuate through the seasons. Ice accumulates as seawater freezes during colder months and melts away during the warmer months. But the ice never quite disappears entirely at the poles. In the Arctic Ocean, the area the ice covers typically reaches its yearly minimum in September. Since scientists at NASA and the National Oceanic and Atmospheric Administration (NOAA) began tracking sea ice at the poles in 1978, sea ice extent has generally been declining as global temperatures have risen.
“While this year’s Arctic sea ice area did not set a record low, it’s consistent with the downward trend,” said Nathan Kurtz, chief of the Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Arctic ice reached its lowest recorded extent in 2012. Ice scientist Walt Meier of the National Snow and Ice Data Center at the University of Colorado, Boulder, attributes that record low to a combination of a warming atmosphere and unusual weather patterns. This year, the annual decline in ice initially resembled the changes in 2012. Although the melting tapered off in early August, it wasn’t enough to change the year-over-year downward trend. “For the past 19 years, the minimum ice coverage in the Arctic Ocean has fallen below the levels prior to 2007,” Meier said. “That continues in 2025.”
Antarctic sea ice nearing annual maximum
As ice in the Arctic reaches its annual minimum, sea ice around the Antarctic is approaching its annual maximum. Until recently, ice in the ocean around the Southern pole has been more resilient than sea ice in the North, with maximum coverage increasing slightly in the years before 2015. “This year looks lower than average,” Kurtz said. “But the Antarctic system as a whole is more complicated,” which makes predicting and understanding sea ice trends in the Antarctic more difficult.
It’s not yet clear whether lower ice coverage in the Antarctic will persist, Meier said. “For now, we’re keeping an eye on it” to see if the lower sea ice levels around the South Pole are here to stay or only part of a passing phase.
A history of tracking global ice
For nearly five decades, NASA and NOAA have relied on a variety of satellites to build a continuous sea ice record, beginning with the NASA Nimbus-7 satellite (1978–1987) and continuing with the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager Sounder on Defense Meteorological Satellite Program satellites that began in 1987. The Advanced Microwave Scanning Radiometer–for EOS on NASA’s Aqua satellite also contributed data from 2002 to 2011. Scientists have extended data collection with the 2012 launch of the Advanced Microwave Scanning Radiometer 2 aboard a JAXA (Japan Aerospace Exploration Agency) satellite.
With the launch of ICESat-2 in 2018, NASA has added the continuous observation of ice thickness to its recording. The ICESat-2 satellite measures ice height by recording the time it takes for laser light from the satellite to reflect from the surface and travel back to detectors on board.
“We’ve hit 47 years of continuous monitoring of the global sea ice extent from satellites,” said Angela Bliss, assistant chief of NASA’s Cryospheric Sciences Laboratory. “This data record is one of the longest, most consistent satellite data records in existence, where every single day we have a look at the sea ice in the Arctic and the Antarctic.”
By James Riordon
NASA Goddard Space Flight Center
Media contact: Elizabeth Vlock
NASA Headquarters
