The ice covering the Arctic reaches its minimum every September, thanks to the warm summer heat. Since the end of the century, this minimum has become increasingly pronounced. According to NASA data, based on several of its satellites, the extent of the polar ice cap has been shrinking at a rate of 12.6% every decade since 1980. But climate variability itself makes it difficult to know when the entire Arctic Ocean will be water. Now, a study supported by observations from NASA and ESA satellites and a sophisticated climate model predicts that, between 2030 and 2050, the first September will arrive without ice. And if greenhouse gas (GHG) emissions are not reduced, by 2100 the Arctic region will be ice-free for almost half a year.
Until the beginning of the century, trying to navigate the Northwest Passage (the one that connects the Atlantic Ocean with the Pacific through northern Canada) was an adventure restricted to summer and aboard an icebreaker ship. The situation was somewhat better in the Northeast Passage (through the far north of Russia), where ships could afford a couple of months a year. Today, both routes are relatively safe in summer, so much so that there are tourist cruises on old icebreakers. But the Arctic Ocean resists circumnavigation: even today, the Wandel Sea, the portion that connects to northern Greenland, remains frozen all year round. But according to a new study published today in the scientific journal Nature Communications, ships could even reach this area and the very center of the North Pole in a few years.
"We see that the Arctic Ocean will be ice-free in summer between 2030 and 2050 in all emission scenarios we consider," Seung-Ki Min, a researcher at the Climate Change Research Laboratory at Pohang University (South Korea), co-author of the study, said in an email. It should be borne in mind that future emissions scenarios correspond to the objective of not exceeding the 2º of extra warming that was approved in the Paris Agreement of 2015, This is the most optimistic scenario, so it seems that the thaw is inevitable. But it also means that, as Min says, "we can avoid an ice-free Arctic in summer if we manage to reduce GHG emissions more aggressively, as in the alternative 1.5º warming route." The problem is that, according to several studies, this limit of increase in the global average temperature has already been exceeded regionally and globally could be exceeded in less than five years.
Read moreThese are the global consequences of melting Arctic ice
The work led by Min is based on the evolution of Arctic ice followed by several satellites, with data dating back to 1979 and reaching until 2019. One of the contributions of these 40 years of data is that, at least since the late 90s, the polar ice cap loses ice every month, not only in summer. Since the end of the last ice age, the annual cycle of the Arctic followed the same pattern: the extent of the Arctic sea ice reached its maximum extent between March and April, to diminish the following months, until its minimum between September and October, when it began the cycle again. But all the data points out that the icy portion of the ocean is getting smaller every new March, so there is also melting even in the coldest years, even if it is on the margins.
"Previous work had observed melting throughout the year, but our study confirms that the decline in Arctic sea ice in all months is mainly due to the increase in human-induced greenhouse gases," Min said. It is the other great contribution of this work, the confirmation of human responsibility. The Sun, its rays and heat, are what melt the Arctic sea ice. But there are agents that can mitigate or aggravate the action of solar radiation. The natural atmospheric agent that affects the most is volcanic emissions. The particles act as a parasol, cooling. Other particles, these caused by industry, cars and human heating, also have their role. What they have seen is that neither natural nor artificial particles are being decisive: their cooling capacity cannot counteract the warming caused by carbon dioxide (CO₂) and the rest of GHG.
"Almost all of the melting we've seen in recent decades has been caused by us humans."
Dirk Notz, Deputy Director of the Institute of Oceanography, University of Hamburg
The deputy director of the Institute of Oceanography at the University of Hamburg, Dirk Notz, is one of the leading experts on Arctic ice dynamics. In fact, he was one of the main authors of the sixth and final report of the Intergovernmental Panel on Climate Change (IPCC) and co-author of the section dedicated to the ocean, cryosphere and sea level. Notz is also a co-author of this new study on Arctic melting and insists on human responsibility: "We quantified the human impact on the massive loss of sea ice observed in the Arctic by up to 90%. This means that almost all of the melting we've observed in recent decades has been caused by us humans."
The authors of the work used the latest system to model the evolution of the climate, known as CIMP6, capable of running several climate models at once, with a huge amount of data and needing great computing power. To validate their results about the future, they compared those obtained by CIMP6 over the last 40 years and compared them with the real ones recorded by the satellites. "We saw that in all future scenarios considered, including the most optimistic scenario with substantial reductions in greenhouse gas emissions, the Arctic will be ice-free for the first time in September before 2050. This means that it is already too late to continue protecting Arctic summer sea ice as a landscape and as a habitat – it will be the first major component of our climate system that we will lose due to our emissions."
Although going beyond 2050 introduces more uncertainty, things will get worse as the century progresses. The study predicts that, by 2100 and in the worst of the predicted climate scenarios (in which GHGs are not reduced and the current rate of emissions is maintained), the Arctic would be ice-free between May and October. The consequences of half a year without Arctic sea ice would be enormous.
Despite what it may seem, melting ice will not lead to a rise in sea level. Unlike land ice accumulated in Greenland or Antarctica, Arctic ice is already in the water, so nothing to worry about here. But so many ice-free months will accelerate climate change: frozen water has the greatest albedo effect on nature after snow. That turns the North Pole into a giant mirror that reflects much of the sun's radiation, cooling the region. But, thawed, a sea enriched by oxygen from fresh water darkens, absorbing more solar energy. So the melting caused by global warming increases global warming.
The environmental consequences have already been observed since the beginning of the century. Many marine mammals need a minimal amount of ice to breed and rest (such as seals and elephant seals) or to hunt, such as foxes and Arctic bears. In principle, an ice-free Arctic Ocean half the year could be good for large marine mammals, whales. But after the thaw, humans will arrive. Shipping companies, mining companies, fishing boats, cruises with tourists... The growing thaw is provoking a series of geopolitical movements that could reconfigure much of the world order.
"An ice-free Arctic Ocean means that competition for resources and shipping across what China calls the Polar Silk Road could become a reality sooner than expected."
Kristina Spohr, Professor of International History at the London School of Economics (UK)
"An ice-free Arctic Ocean means that competition for resources (fishing, oil and gas exploration) and shipping through what China calls the Polar Silk Road could become a reality sooner than expected," says Kristina Spohr, professor of international history at the London School of Economics. From Berlin, where he was speaking on a panel on Russia, the Ukrainian war and the Arctic, Spohr believes that "there will be more tension between what are considered international and national open waters: international waters must be governed in novel ways (fishing, shipping, exploration from the seabed); but domestic waters and ports will pose security concerns and therefore we will see more militarisation, but it will also attract non-Arctic actors such as investors in ports and other mining infrastructure and resources (China, but also Japan, Singapore, Southeast Asia, India and European countries)."
For this expert in geopolitics, "the melting of the Arctic and the thawing of the world order, due to climate change, the war in Ukraine and tectonic shifts in the international balance of power as China and Russia push for a post-Western world order and a multipolarity that exceeds the rules imposed after the fall of the [Berlin] Wall], entails risks for the indigenous peoples of the Arctic, for the regional ecology, flora and fauna and the situation of the region in general." A region that, as Spohr recalls, "since the late 1980s has been considered an exceptional zone of peace," protected by ice.
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