Under warm summer conditions, the sea ice stretching across much of the Arctic Ocean shriveled much more dramatically than it did during cooler summers of decades past, the National Snow and Ice Data Center has reported.

“While it wasn’t a new record low, this year’s sea ice minimum is yet another example of a changed Arctic environment,” said Walt Meier, an NSIDC senior research scientist.

Every year, the Arctic’s floating sea ice shrinks under summer warmth, typically reaching a minimum extent in September. This year, the sea ice appears to have bottomed out on Sept. 11, continuing a long-term downward trend driven in large measure by human-caused warming.

Along with the paltry amount of sea ice across the Arctic Ocean, other signs were a reminder (as if any was needed) that the Arctic has warmed nearly four times faster than the globe overall. These signs included significant amounts of open water near the North Pole. And at the end of July, that helped a cruise ship carrying marathon runners to reach the pole, where they participated in a slushy race.

Sea Ice Bottoms Out

By Sept. 11, the sea ice had shriveled to 4.28 million square kilometers, or 1.65 million square miles, according to the NSIDC. That’s the seventh lowest minimum extent in the nearly 46-year satellite record.

The ice coverage was about 749,000 square miles less than the 1981 to 2010 average minimum extent — an area of ‘missing’ ice slightly larger than Alaska, by far the biggest U.S. state.

This means the last 18 years, from 2007 to 2024, have seen the lowest 18 sea ice extents on record. (One caveat: Changing winds or late-season melting could still reduce the Arctic ice extent further.)

The Sun has now dipped below the Arctic horizon, and air temperatures are falling as winter begins enveloping the region. This will promote the expansion of sea ice until spring.

Open Water Near the Pole

Signs of a watery summer environment around the North Pole are visible in this image acquired by NASA’s Terra satellite on Sept. 10, one day before the sea ice minimum:

In an email exchange, I asked Meier how unusual this is. Here’s part of his response:

In summer, “there has always been some amount of open water near the North Pole due to the formation of leads (cracks) in the ice. In the past, the ice was very thick and the cracks quite narrow — maybe a couple hundred meters wide (though they could extend many kilometers in length). But in recent years, there is much more open water and the ice is thinner and more broken up — a bunch of individual floes amidst open water instead of small cracks in a largely consolidated sheet of ice.”

How did this summer compare to previous years?

“Not every year has been as extreme as this year,” Meier replied. “It depends on weather conditions, particularly winds. But we’ve seen some relatively open conditions.”

Meier recalled that during an Arctic expedition in 2019 and 2020, researchers were able to sail from Norway’s Svalbard archipelago “right up to the pole with almost no resistance. There was still quite a bit of ice around, but it was smaller floes, not very compact, making it easy for the icebreaker to get through.”

This year, a similar journey was made by the Commandant Charcot, a luxury hybrid-electric polar exploration ship fueled by liquid natural gas.

The vessel carried runners determined to complete one of the most unusual races on Earth: the North Pole Marathon. Oliver Wang, the race director told me in an email that instead of breaking ice all the way, the ship was able to navigate through openings in the sea ice, with the help of advanced technology.

On July 31, 18 runners completed the marathon on an ice floe. They ran a .22-mile loop 120 times to complete the 26.2 marathon distance. The temperature was -1°C (30°F), but with the windchill, it felt like -9°C (16°F). “The underfoot terrain was very challenging, with runners describing it as akin to running on sand,” Wang says.

But instead of sand, it was actually the slushy surface of the floe.

Other than small leads in the ice, large amounts of open water near the North Pole “is something that never really happened in the past,” Meier said in his email. “The North Pole used to be covered by thick, 3-to-4-meter-thick old ice. Now it is either first or second-year ice that is at most maybe 2.5 meters thick and which is more easily broken up into smaller floes that can then disperse, allowing more open water.”

Antarctic Sea Ice is Suffering Too

Meanwhile, the extent of sea ice fringing the Antarctic continent reached its own minimum extent back in late February — the end of summer in the Southern Hemisphere. The ice extent bottomed out as second lowest during the period of satellite observations, prompting Ted Scambos of the Cooperative Institute for Research in Environmental Sciences to describe the situation as “nothing short of shocking.”

Since then, winter conditions have caused sea ice to grow — but quite slowly compared to the long-term average. The expansion of the ice has tracked at its second lowest level for most of the growth season, according to the NSIDC.

The winter growth season in Antarctica is now waning, and it’s looking likely that the sea ice around the continent will end up there — as the second most paltry maximum extent on record. An official ranking should be forthcoming from the NSIDC soon.