It’s already too late. The Arctic Ocean could be free of ice by the 2030s even if we bring down greenhouse gas emissions significantly between now and then, according to a new study. This is sooner than most scientists had thought possible for an ice-free Arctic and is yet another sign the climate crisis is happening faster than expected.
Researchers led by Yeon-Hee Kim of South Korea’s Pohang University of Science and Technology used observational data from 1979 to 2019 to project sea ice decline in the Arctic. They found that human-caused emissions are the main factor affecting sea ice decline and that the first ice-free September is due to happen soon.
“We may experience an unprecedented ice-free Arctic climate in the next decade or two, irrespective of emission scenarios. This would affect human society and the ecosystem both within and outside the Arctic, through changing Arctic marine activities as well as further accelerating the Arctic warming,” the researchers wrote.
A changing climate
The Arctic is undergoing rapid climate heating, outpacing any other region on Earth. Scientists have focused their attention in recent years on the sea ice that blankets a big portion of the Arctic Ocean during winter. This delicate layer of frozen seawater fluctuates in size throughout the year, reaching its smallest extent in September.
The ice that persists through the summer is known as multiyear sea ice and is thicker compared to seasonal ice. It serves as a barrier, restricting the exchange of moisture and heat between the ocean and the atmosphere. Over the past four decades, the extent of multiyear sea ice has diminished from seven to four million square kilometers.
Researchers have long been trying to determine when the Arctic Ocean might become ice-free in summer, defined as when the sea ice drops below one million square kilometers. This threshold is used mainly because thicker ice along parts of Canada and northern Greenland is expected to remain after the rest of the Arctic Ocean is ice-free.
The new study contrasts with the latest report by the UN Intergovernmental Panel on Climate Change (IPCC). The IPCC said that the Arctic would likely be "practically ice-free" by the middle of the century, based on both intermediate and high emissions scenarios. However, the study proposes an earlier timeline, irrespective of the emission scenarios.
An ice-free Arctic Ocean is expected to accelerate global warming as it reduces the amount of sunlight absorbed by the ocean – a process known as positive feedback. This, in turn, can accelerate the melting of the Greenland ice sheet, already a big driver of sea level rise. The loss of sea ice can also change the ocean's biological activity.
“We need to prepare ourselves for a world with warmer Arctic very soon,” Min told CNN. “Since Arctic warming is suggested to bring weather extremes like heatwaves, wildfires, and floods on Northern mid- and high latitudes, the earlier onset of an ice-free Arctic also implies that we will be experiencing extreme events faster than predicted.”
The study was published in the journal Nature.