First ice-free day in the Arctic Ocean could come before 2030

Since 1979, when satellites made it possible to measure its extent faithfully, the Arctic Ocean has been losing almost 80,000 km² (30,888 m²) of ice every year. The amount is equivalent to the land mass of the U.S. state of Maine and this has been happening for nearly half a century. In 2023 the Arctic ice sheet reached an all-time low, and the four major lows have all occurred in this century. Some time ago, scientists modeled when the first year would come in which, at the end of the summer, there would be nothing but sea. More recently, researchers calculated that the melt would occur one September in the next 20 years. Now, scientists who have been studying the region for over a decade have modeled and estimated when the first ice-free day in the Arctic will occur.

Supported by the most advanced climate models, the researchers simulated the evolution of the Arctic ice floe starting from the situation of 2023, when its extension marked one of its historical minimums, with 3.3 million km² (the Arctic has a total extension of more than 16 million km²). What they have found is that, whatever we do in terms of greenhouse gas emissions now, that first ice-free day is already inevitable. Although if emissions are drastically reduced, the number of ice-free days beyond this first one could be minimized.

In reality, the Arctic is not going to become completely ice-free, but scientists use the term “ice-free” to refer to the (historic) moment when the Arctic’s ice extent drops below 1 million km². Alexandra Jahn, University of Colorado at Boulder researcher and co-author of the new paper, published in Nature Communications, explains: “This threshold has been used for more than a decade in scientific studies, because, although the sea ice area of one million km² is not small in absolute terms, it is north of Greenland and the Canadian Arctic archipelago, leaving 93% of the Arctic Ocean free of sea ice.” There will be ice, but it will no longer be a frozen ocean.

Of the nearly 400 projections the researchers have made, most indicate that this first ice-free day will take place in the next few years. It could even arrive as early as the summer of 2027. “But an ice-free Arctic within three years, the fastest transition we found in the simulations, is very, very unlikely,” Jahn notes. “That’s one of 366 simulations we evaluated, so based on the ones we analyzed, that gives a probability of less than 1%,” she adds. The percentage goes up to 2.5% if the time span is the end of this decade. “However, that said, we live in a materialization of reality, whereas the models give us many possibles. So, although unlikely, even low-probability events can happen in the one timeline we will experience,” she concludes.

Céline Heuzé, a climatologist at the University of Gothenburg (Sweden) and co-author of the study, prefers not to center on percentages or probabilities of when the day will come. “We can’t put a number on the probability, because at the moment, whether we have an ice-free day or not depends on the chaotic weather,” she says. What the researchers do maintain is that a series of extreme weather events could melt two million km² or more of sea ice in a short period of time. This is what they call a RILE, or rapid sea ice loss event. Simulations indicate that the first ice-free day will come after one of these events.

On the effects of this first ice-free day when it arrives, “it will obviously have a symbolic value,” says Heuzé. However, “it won’t change things drastically,” notes Jahn. Impacts — on the ice itself, on ecosystems, and even on geopolitics — have already been evident in recent years. But Jahn also says that “the more sea ice area we lose, the greater the impacts of sea ice loss; so nothing magical happens with a million km² that hasn’t happened with 1.5 million km². But at about 1 million km², it means that most of the Arctic is ice-free and therefore easily navigable even for non-ice-strengthened ships.” Not only will the Northwest Passage be opened to shipping, the entire Arctic will be.

What will not change is the sea level. Arctic water masses are always the same, whether they are mostly frozen (early spring) or thawed (late summer). It only changes from a solid to a gaseous state. But the fact that the Arctic will be ice-free for more and more days in the coming years will carry many serious consequences, some regional, some global. Among the first, the fact that most of the ocean will be navigable will have profound consequences for cetaceans and other marine mammals. In addition, the increased amount of liquid water will increase regional warming, as the dark blue absorbs more radiation — heat — than ice, which has the greatest albedo effect (the rebound of radiation) after freshly fallen snow.

This reduction in Arctic albedo is also key to explaining global warming, which is expected to accelerate with a shrinking Arctic ice sheet. There is another effect, the extent of which science is only beginning to understand: instability in the Arctic appears to be related to alterations in global atmospheric circulation and, in mid-latitudes, to the increase in extreme events such as the recent floods in Valencia.

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