World's sea-ice falls to record low

The world's frozen oceans, which help to keep the planet cool, currently have less ice than ever previously recorded, satellite data shows.

Sea-ice around the north and south poles acts like a giant mirror by reflecting much of the Sun's energy back into space.

But as rising temperatures cause this bright layer to shrink, the dark ocean below can absorb more heat, warming the planet further.

This latest sea-ice low appears to have been driven by a combination of warm air, warm seas and winds breaking apart the ice.

At the other end of the planet, the Arctic should be reaching its annual maximum, with cold winter temperatures helping the oceans to freeze over.

But current sea-ice extent is nearly 0.2 million sq km below anything previously recorded for the time of year, and has been tracking very low since late 2024.

This is partly as a result of a late freeze-up of ice around Hudson Bay, with unusually warm ocean waters taking a long time to cool down.

As well as warmer seas, some storms also disrupted ice around the Barents and Bering Seas, with the consequences likely amplified by long-term reductions in sea-ice thickness.

"A thinner ice cover is more responsive to weather [… so] weather events can have a stronger impact than they used to," said Julienne Stroeve, professor of polar observation and modelling at University College London.

In recent weeks, Arctic sea-ice has moved even further below average. Temperatures around the north pole were about 20C above normal in early February, leading to melting conditions in places like Svalbard.

This "is quite astonishing" for the time of year, according to Dr Bracegirdle.

This very low winter extent doesn't necessarily mean the Arctic will end up with record conditions throughout 2025, as conditions can change quickly at the poles.

But, with the Arctic warming nearly four times faster than the global average, declines over the coming decades are almost inevitable.

The Arctic is expected to be essentially free of sea-ice at the end of its summer at least once before 2050, according to the UN's Intergovernmental Panel on Climate Change. Some recent studies suggest it could happen sooner.

Declining sea-ice at both poles not only has implications for local wildlife like polar bears and penguins, but also the Earth's climate.

Polar sea-ice has already lost around 14% of its natural cooling effect since the early-to-mid 1980s, as the area of bright, reflective ice has declined, according to a study published last year.

"If you significantly change the sea ice distribution in and around Antarctica, you modify that part of the planet which is actually helping us fight against climate change," said Simon Josey, a professor at the National Oceanography Centre.

Sea-ice also plays an important role in the great ocean conveyor, the mass movement of water that helps distribute heat around the planet and keeps places like the UK and north-west Europe relatively mild.

"If we see another strong winter loss [of Antarctic sea-ice], people are going to start to worry about what it's doing to the ocean circulation," said Prof Josey.

Additional reporting by Becky Dale