Using advanced climate models, researchers have simulated Arctic ice trends starting from 2023, when ice loss was just 3.3mn square kilometres (out of a total area exceeding 16mn sq km). Their findings indicate that even with sharp cuts to greenhouse gas (GHG) emissions, the initial ice-free day is unavoidable. However, reduced emissions could limit the number of such days in the future.

In recent years, satellites have allowed precise tracking of Arctic ice loss, revealing an average annual decline of about 80,300 sq km. This reduction, comparable to the US state of Maine, has persisted for decades.

By 2023, Arctic sea ice had hit its lowest recorded level, with the four most significant declines all having occurred this century.

Scientists have long predicted the first summer when the Arctic would be almost entirely sea. Recent estimates suggest this milestone will happen within the next two decades, with new studies modelling when the first completely ice-free day may arrive.

The term "ice-free" as used by climate and ocean scientists refers to when Arctic ice coverage drops below 1mn sq km, a definition used for over a decade in scientific research. According to Alexandra Jahn from the University of Colorado at Boulder, this remaining ice would be concentrated near Greenland and the Canadian Arctic, leaving 93% of the ocean open. While patches of ice will persist, the Arctic as a whole will no longer resemble its historically frozen state.

Among nearly 400 simulations, most models suggest the first ice-free day is only a few years away, potentially as soon as 2027. However, Jahn emphasises that the earliest scenario, three years from now, is highly improbable, with less than a 1% chance based on their analysis. The likelihood increases slightly, reaching 2.5% by the end of the decade. Still, she warns that low-probability events are possible because models provide a range of outcomes, while reality plays out in just one.

Céline Heuzé from the University of Gothenburg in Sweden, another co-author, avoids focusing on specific probabilities. She notes that whether this event occurs soon depends heavily on unpredictable weather patterns. Researchers agree that extreme weather could trigger rapid ice loss, known as a RILE (rapid ice loss event), potentially melting over 2mn square km in a short time. Such an event is likely to precede the first ice-free day.

Regarding its implications, Heuzé describes this event as symbolically important but not transformative.

Jahn adds that the impacts of ice loss – on ecosystems, the environment, and geopolitics – are already evident and growing. She explains that reaching a 1mn sq km loss does not signify a sudden change but highlights how much of the Arctic Ocean will become navigable. Once this happens, even ships without icebreaker capabilities will traverse areas like the Northwest Passage and beyond.

As ice diminishes, regional and global impacts will intensify. More exposed water absorbs sunlight instead of reflecting it like ice, accelerating local warming. This phenomenon, tied to the loss of the Arctic’s reflective surface, is a significant driver of global temperature rise.

Scientists are also investigating how Arctic instability influences global weather patterns. Some research suggests a link between changes in Arctic conditions and extreme weather events in other regions.