A previously recorded slowdown in Arctic sea ice decline has ended, according to a new study, with the largest year-to-year wintertime reduction ever recorded.

In a study published last summer, researchers found that melting sea ice in the Arctic had slowed down over the past 20 years, with no statistically significant decline in its extent recorded between 2005 and 2024.

Given the increase in global temperatures during this period, the finding was surprising.

However, the researchers said natural variations in ocean currents that limit ice melting probably balanced the rise in global temperatures. They said this was only a temporary reprieve and melting was highly likely to start again at about double the long-term rate at some point in the next five to 10 years.

Just two years later, the new study has found the slowdown in sea ice decline is now over.

Using the most recent satellite observations of sea ice coverage, the researchers found that the 2005 to 2024 slowdown was “temporary rather than sustained”.

Dr Duo Chan, lead author of the paper from the University of Southampton’s School of Ocean and Earth Science, said that what “looked like a pause in the early 2020s now appears to have just been a temporary slowdown within a longer-term decline”.

Sea ice area in September, when it reaches its annual minimum, has halved since 1979, when satellite measurements began.

The researchers found that between 2024 and 2025 Arctic sea ice declined by 5.8%. This is the largest year-to-year wintertime drop ever recorded.

Dr Alessandro Silvano, co-author of the paper at the University of Southampton, said this sharp drop in 2025 was unusual, but physically plausible under current Arctic warming.

Because the winter sea ice acts as an insulator between the relatively warm Arctic ocean and the much colder atmosphere, a reduction in ice will mean more ocean heat and moisture will enter the atmosphere.

The authors say this can affect pressure patterns, storm development and large-scale atmospheric circulation, affecting the weather farther south.

Chan said the study acted as a warning of the ongoing climate crisis.

“Short-term recoveries can temporarily obscure the longer-term direction of Arctic sea ice change. The low winter sea ice extents in 2025 and 2026 clearly show that Arctic sea ice loss has not stopped – it is continuing in a warming climate,” he said.