All the extra heat from the summer is also captured in the Arctic Ocean, and then released throughout the winter. “The greatest warming in the Arctic happens in the winter, which may surprise people because you have the largest sea ice melt in the summer,” says Hahn, of the University of Washington. “That’s when you have incoming sunlight. But the idea is that there is seasonal ocean heat storage.” It’s like a giant radiator heating a room, even after it’s turned off.
At the same time, storms have transported moisture from lower latitudes into the Arctic, which has further encouraged the development of clouds. And injections of warmer water from the south, brought north by ocean currents, further melting sea ice. “When it melts, water evaporates and increases the humidity, causing an increase in haze in the winter, and we have infrared radiation coming from these clouds to the surface,” says Chylek. “This is a feedback loop that could cause Arctic temperatures to rise, and we believe that is one of the reasons why we are seeing this rise in temperature around 2000.”
Climate scientist Cecilia Bitz of the University of Washington, who is studying Arctic amplification but was not involved in the new research, points out that there has been a delay in how high-latitude areas have responded to greenhouse gases compared to the rest of the planet. It has taken time for the sea ice to melt, but now that it is doing so, the heat feedback loop in the Arctic has worsened and the rate of change has become much more noticeable. “The tropics warmed up faster first, and now the Poles are catching up, and that’s why you see a trend,” she says.
The consequences are already massive and far-reaching. First and foremost, more melting – especially in Greenland, which is losing one quarter trillion tons of ice each year – means higher sea levels. In addition, warmer water becomes physically larger, a phenomenon known as thermal expansion, which further raises sea levels.
The landscape also suffers from literal and metaphorical upheaval. Warming temperatures are thawing frozen soil known as permafrost. When the permafrost loses water, it collapses and pulls any infrastructure down into or over it, such as pipelines, roads and buildings. “There is people in the Arctic, ”says Bitz. “They did very little to deserve living in this dangerous environment.”
Cloud-rocking temperatures also make this landscape greener. Shrub species march north, and the vegetation catches more snow toward the ground. This prevents the cold of winter from penetrating it, potentially speeding up the thawing of permafrost. All the extra vegetation is also darker – just as the sea itself is darker than the ice – and thus absorbs more of the sun’s radiation.
In short, the Arctic is falling into climatic and ecological uncertainty. “Every summer when my field research team goes to the Arctic, we do not quite know what to expect,” said Isla Myers-Smith, a global change ecologist at the University of Edinburgh who was not involved in the new research. “This year we arrived in Inuvik, Canada, in a heating dome with temperatures reaching 32 Celsius [90 degrees Fahrenheit]but out on the coast there was still plenty of sea ice around, which kept the temperature much cooler locally. “
This kind of variation makes it difficult for models to determine how the Arctic is changing and to predict how these changes will continue to affect the larger climate system. That is why it is so important for scientists to revise their understanding that the Arctic is actually warming more than four times just as fast as the rest of the planet.
A major concern is the potential for the climate system to reach a turning point where warming starts rapid change. If the Arctic is warmed up enough, e.g. melting in Greenland is rapidly accelerating. “I do not think it is exactly known – if these turning points exist – what level of warming would trigger such rapid changes,” said Michael Previdi, a climate scientist at Lamont-Doherty Earth Observatory at Columbia University who was not involved in it. new leaves. But he continues, in theory, a larger gain increases the “chances of passing one of these tipping points.”