Arctic sea ice ties for tenth-lowest summer minimum

Arctic sea ice shrank to its smallest extent of the year on 12 September, covering about 4.6 million square kilometres, according to NASA and the US snow and ice data centre in Colorado, which tracks polar ice.

That tied with 2008, 2010 and 2025 for the tenth-lowest minimum since satellite records began in 1978.

A record winter low

The decline is visible at both ends of the year. The ice reaches its greatest extent each March, and the 2026 winter maximum tied with March 2025 as the lowest ever recorded.

Every summer from 2007 to 2026 ranks among the 20 lowest September extents on record. The smallest ever was in September 2012.

A pause in summer losses

The rate of summer ice loss has not been steady. Over the past decade, September ice cover has stayed relatively stable after falling rapidly in the 2000s. Scientists say short-term weather has a strong influence on how much ice melts in any one summer, and NASA researchers have identified more cloud over the Arctic in recent years, which reduces the sunlight reaching the ice, as one reason for the slowdown.

Even so, September ice remains far below its historical average.

Younger, thinner ice

The ice itself is changing. In the past, much of the Arctic was covered by multi-year ice, which survives at least one summer and grows thicker and more resilient. Satellites show that multi-year ice has declined sharply, and the Arctic is now increasingly covered by thinner first-year ice that forms in winter and melts more easily.

Why it is happening

Natural patterns such as the Arctic Oscillation, which affects winds and temperatures, cause changes from year to year. But scientists say natural variability cannot explain the long decline since 1978. Rising global temperatures, together with natural variability, have driven the loss. They project the Arctic Ocean could become essentially ice-free in summer at least once before the middle of this century.

How it is measured

Satellites measure sea ice using microwave sensors, which detect the energy naturally given off by the Earth's surface. Ice gives off more than open water, and microwaves pass through cloud, so the Arctic can be monitored even in bad weather. The record began with NASA's Nimbus-7 satellite and now includes data from a Japanese satellite.

Why it matters

Sea ice reflects most of the sunlight that hits it, while dark open water absorbs it, so less ice means more warming, a feedback that helps explain why the Arctic is warming several times faster than the global average. Changes in the Arctic can also affect weather patterns further south, including the jet stream that steers storms towards the UK, although the links are still being researched.

Melting sea ice does not itself raise sea levels much, because the ice is already floating, but the warming that drives it also melts land ice in Greenland, which does.