Satellite data reveals that the world’s frozen oceans, crucial in maintaining Earth’s temperature balance, have reached their lowest levels ever recorded.

Sea ice around the Arctic and Antarctic acts as a massive reflective surface, bouncing much of the Sun’s energy back into space. However, as global temperatures rise, this icy shield is shrinking, exposing the darker ocean beneath. This exposed water absorbs more heat, leading to further warming and accelerating the cycle of ice loss.

This recent record-low sea ice extent is attributed to a combination of warm air, warm ocean waters, and winds that break apart the ice. Between February 8 and 13, the total sea ice coverage across both poles was measured at 15.76 million square kilometres (6.08 million square miles). This figure, analysed from data by the U.S. National Snow and Ice Data Center (NSIDC), surpasses the previous five-day record low of 15.93 million square kilometres (6.15 million square miles) set in early 2023.

At present, Arctic sea ice is at its lowest recorded extent for this time of year, while Antarctic sea ice is nearing a historic minimum in satellite records that date back to the late 1970s.

The decline of Arctic sea ice due to a warming planet is well-documented. In the 1980s, the end-of-summer extent averaged 7 million square kilometres; by the 2010s, this had dropped to 4.5 million square kilometres.

Antarctic sea ice, however, demonstrated resilience until the mid-2010s, defying projections that it would diminish significantly. Since then, a pattern of very low sea ice extents has emerged, though natural variability remains a factor.

“Every year, every data point that we get suggests that this isn’t a temporary shift, but something more permanent, like what we’ve seen in the Arctic,” Walter Meier, senior research scientist at NSIDC, said.

“It is indicating that the Antarctic has moved into a new regime of lower ice extents.”

Unlike the Arctic, which is surrounded by land, Antarctic sea ice is surrounded by ocean, making it particularly susceptible to the influence of winds that break it apart.

Warm air and ocean temperatures appear to be major contributors to the latest record-low Antarctic sea ice extent, particularly during the southern hemisphere’s summer months. In addition, the Antarctic ice shelves—extensions of the continent’s ice flowing into the ocean—experienced an exceptionally intense season of surface melting, driven by unusually high air temperatures.

“Atmospheric conditions in December and January looked like they were strongly promoting surface melting on the ice-shelves,” said Tom Bracegirdle, research scientist at the British Antarctic Survey.

“That could also have contributed to what we’ve seen in Antarctic sea-ice, and ongoing ocean warming is setting the backdrop to all of this as well.”

A recent study indicated that the record-low Antarctic sea ice extent observed in 2023 would have been a one-in-2,000-year event without the influence of climate change. Now, in 2025, sea ice levels are approaching a similarly extreme low.

In the Arctic, sea ice should currently be expanding to its annual maximum, aided by cold winter temperatures. However, the current extent is nearly 0.2 million square kilometres below any previously recorded level for this time of year. The Arctic has been tracking at historically low levels since late 2024.

A delayed freeze-up in Hudson Bay has played a role in this decline, as unusually warm ocean waters took longer than usual to cool. Additionally, storms in the Barents and Bering Seas disrupted ice formation, with long-term reductions in sea ice thickness exacerbating the effects of these disruptions.

“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.

Over the past few weeks, Arctic sea ice has dropped even further below average levels. In early February, temperatures around the North Pole were approximately 20°C above normal, leading to melting conditions in places like Svalbard.

Dr. Bracegirdle, a climate expert, described this phenomenon as “quite astonishing” for this time of year. However, he noted that while this exceptionally low winter ice extent does not necessarily mean that 2025 will set records for low ice throughout the year, Arctic conditions can change rapidly.

Nevertheless, long-term trends indicate that Arctic warming is happening nearly four times faster than the global average. As a result, continued declines in sea ice are expected in the coming decades. According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), the Arctic is projected to experience at least one ice-free summer before 2050, with some studies suggesting it could happen even sooner.

The loss of sea ice at both poles has far-reaching consequences, not just for wildlife such as polar bears and penguins, but also for the global climate. Since the early-to-mid 1980s, the Earth has lost around 14% of the cooling effect provided by polar sea ice, as the reflective ice surface has diminished.

“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 a vital role in the great ocean conveyor belt, a global system of ocean currents that distributes heat across the planet. This system helps moderate temperatures in regions like the UK and northwest Europe. A weakening of this circulation due to declining sea ice could have dramatic consequences for global weather patterns, potentially leading to more extreme weather events.

“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.

The ongoing loss of polar sea ice underscores the urgency of addressing climate change. Without significant efforts to curb greenhouse gas emissions and slow global warming, the planet is likely to see further disruptions to its delicate climate balance in the years to come.