The Arctic Ocean is a vast expanse of frozen seawater that expands and contracts with the seasons. Ice typically accumulates during the long, dark winter, reaches its maximum extent in March and retreats during the warmer months to a minimum in September.

Although this seasonal cycle has continued for thousands of years, satellite measurements show that the amount of Arctic sea ice has decreased significantly at both ends of the cycle.

Arctic sea ice reached one of its lowest September levels in 2026

In 2026, Arctic sea ice reached its annual minimum extent on September 12, covering approximately 4.6 million square kilometers (1.78 million square miles). According to NASA and the National Snow and Ice Data Center (NSIDC), this tied the lowest levels recorded in 2008, 2010 and 2025. It was also the 10th-lowest September extent since satellite monitoring began.

The map compares Arctic sea ice conditions in September since 1990, when coverage is typically at its lowest, with conditions in March of the following year, when ice approaches its annual maximum. The sequence continues through March 2026.

Decades of Arctic sea ice loss

Satellites have continuously tracked the seasonal expansion and retreat of Arctic sea ice since late 1978, providing scientists with nearly 50 years of observations. The record shows a long-term decline that accelerated during the 2000s, with ice levels remaining unusually low.

Every summer from 2007 through 2026 ranks among the 20 lowest September sea ice extents in the satellite record. The smallest extent ever observed occurred in September 2012.

However, the rate of summer ice loss varies from year to year. During the past decade, September sea ice extent has remained relatively stable rather than continuing its earlier rapid decline. Scientists emphasize that short-term weather conditions can strongly influence how much ice melts each summer.

For example, increased cloud cover in the Arctic in recent years has reduced the amount of sunlight reaching the ice, helping to limit further melting. NASA researchers have identified this as a factor contributing to the recent slowdown in melting. Despite this temporary stabilization, September sea ice extent remains far below historical averages.

The Arctic is losing its oldest and thickest sea ice

The changes involve more than the total area covered by sea ice. Scientists have also recorded major changes in the ice itself, which is becoming younger and thinner.

Historically, much of the Arctic contained multiyear ice—ice that survived at least one summer melt season. This ice could persist and accumulate over several years, making it generally thicker and more resilient than ice formed during a single winter.

Satellite observations now show significant losses of multiyear ice. As a result, the North Pole is increasingly covered by thin first-year ice. This ice forms during the colder months but is more vulnerable to melting when summer returns.

The decline is also evident in winter, when Arctic sea ice typically reaches its maximum extent. The March 2026 annual maximum statistically tied the March 2025 maximum as the lowest winter peak in the satellite record.

Could the Arctic Ocean become almost ice-free in summer?

Natural climate patterns influence Arctic sea ice from year to year. One example is the Arctic Oscillation, a pattern of atmospheric circulation that affects temperature, wind and ice conditions across the region.

However, natural fluctuations alone cannot explain the sustained decline recorded by satellites since 1978. Rising global temperatures, along with natural climate patterns, are contributing to the continuing loss of Arctic sea ice.

Scientists predict that the Arctic Ocean could be essentially free of sea ice during at least one summer by the middle of the 21st century. Such an event would bring significant changes to a region that has supported extensive seasonal ice sheets for thousands of years.

How satellites measure Arctic sea ice through clouds

Scientists use satellites equipped with passive microwave sensors to measure Arctic sea ice extent. These instruments detect microwave energy naturally emitted by Earth’s surface, allowing researchers to distinguish frozen seawater from the surrounding open ocean.

Sea ice emits more microwave energy than liquid water, creating a contrast that satellites can detect. Unlike visible-light imagery, microwave measurements can pass through clouds, allowing researchers to monitor the Arctic consistently even when storms or persistent cloud cover obscure the surface.

Continuous satellite observations began in 1978 with NASA’s Nimbus 7 spacecraft. Additional measurements came from the Defense Meteorological Satellite Program (DMSP), which began in 1987, and NASA’s Aqua satellite, which provided observations between 2002 and 2011.

In 2025, researchers began incorporating observations from the Japan Aerospace Exploration Agency’s GCOM-W satellite, continuing the long-term effort to measure changes in Earth’s polar ice.

The satellite map also includes a white circular area at the North Pole known as the “Pole Hole.” This area falls beyond the historical coverage of satellite sensors, meaning direct measurements were not available. When calculating total sea ice area, scientists assume that the region is covered by ice.

Image by Michala Garrison using data from NASA Earth Observatory and the National Snow and Ice Data Center.