For the past five months, Melinda Webster lived on an icebreaker that was frozen in ice floes near the North Pole.
For Webster, a sea ice geophysicist at the University of Alaska Fairbanks, it is the ideal observatory.She and 14 other scientists set off as part of the largest research group Polar expeditions have studied the rapidly disappearing sea ice, which is often covered by dense fog out of the satellite’s line of sight.
Protected by armed guards, the researchers protected themselves from polar bears and spent a lot of time measuring all aspects of sea ice, including the thickness of snow and ice, the depth of surface melting pools, and the reflectivity of ice. They occasionally wear red “life jackets”
Webster smiled and said, “People do fall, including myself.” “But this is only part of it, you know.”
Bravely facing such elements is part of the essential research: sea ice is the leader in Arctic climate change. Due to our increasing greenhouse gas emissions, the surface temperature in the Arctic has been warming rapidly-twice the global average.
Historically, in winter, sea ice covered a vast area of the Arctic Ocean and filled most of the Arctic Circle. But as the temperature increased, it has shrunk by 12% Every ten years since the start of measurement in 1979.
Sea ice coverage fluctuates with the seasons, hitting a low in September, and then forming again as the temperature drops in autumn-and it expands again by 2 to 3 times at the end of the winter in March. Webster and her team investigated the summer situation and the beginning of the “refreeze”. But this year, this growth has been slower than ever. October is coming to an end, and sea ice is at its lowest level in recorded history.
On the German icebreaker Polarstern, the changing ice conditions are obvious. She said that Webster paid special attention to “crossing the North Pole, how easy it is to cross the North Pole, just like the ice is thin.” “It’s easy to break through the ice bag. The ship uses only three engines instead of all four.”
The shrinking and thinning of Arctic sea ice is bad news for polar bears and indigenous people who rely on sea ice for hunting. The disappearance of sea ice has further accelerated the warming. When the white surface is replaced by a dark open ocean, it absorbs more heat and reflects less light.According to a new study Nature CommunicationsBy the middle of this century, this feedback loop may increase global temperature by 0.19 degrees Celsius, almost eliminating the temperature impact of China’s carbon neutrality.
To understand the factors driving the dramatic changes in the Arctic Ocean, let’s take a look at three compelling graphs created by atmospheric scientist Zachary Labe at Colorado State University.
Sea ice has hit a new low in October
The following table clearly shows the overall decline in sea ice. It shows that this year’s sea ice level is much lower than the median value of 1981-2010. This trend means that the previously northernmost ice-covered sea ice is gradually turning into a deep blue open ocean.
In 2020, there are terrible signs of precarious Arctic sea ice. Rabe said that this month broke the record for the lowest sea ice area in October, which was 1.5 million square miles less than the average in the 1980s and larger than India.
This year’s sea ice minimum usually occurs in September after the summer melts, and it is also the second lowest on record since 2012. The figure below shows how the October sea ice recovery lags behind the typical patterns of the past few decades.
What caused most of the Arctic to remain ice-free before the fall? As Andres Flij of the European Severe Weather Organization pointed out, the eastern part of the Arctic Ocean (northern Siberia) was several degrees Celsius higher than the average temperature from 1981 to 2010. These warm temperatures make it difficult for ice to form.
The figure below shows that the sea ice formation in Eastern Siberia, Laptev and Kara Sea (all parts of the Arctic Ocean) is particularly low compared to the recent past.
The consequences of the Arctic Ocean becoming ice-free
The low sea ice area in October this year may remain for some time, but climate scientists expect it to exceed it in the next few years.
Labe said: “We can expect big changes every year, but overall, in the autumn months, the ice sheet will get smaller and thinner.” “Although 2020 is currently a record It’s a low point, but in the near future, it may resemble a typical October.” It is even expected that the Arctic Ocean will be ice-free by the summer of 2050.
The reduction in ice has affected the indigenous peoples who use sea ice to fish for whales and seals. This exacerbated food insecurity-in 2014, when walrus hunting approached, a food bank in Washington provided 10,000 pounds of halibut to indigenous communities in Alaska, Ed Struzik reported for Yale Environment 360.
It also poses a danger to polar bears, which also use ice to find food.A recent study Natural climate change Due to the loss of habitat, the polar bear project will be almost extinct by the end of this century.
As Webster described, ice changes are part of a larger “cascade effect” in which the delayed growth of winter ice causes ice thinning, which is comparable to older thicker seas. Compared with ice, summer ice melts more easily. This creates more open oceans.
This shift contributes to regional and global warming. Where the ice surface of the White Sea reflects sunlight, dark water absorbs heat, which further reduces ice growth. According to the 2019 Arctic Report Card of the National Oceanic and Atmospheric Administration of the United States, the change in albedo (or reflectivity) in the Arctic ocean and land is the main reason for the region’s heating rate being twice the global average rate. one of the reasons.According to recent Nature Communications This research will also make an important contribution to global warming.
Researchers found in a 2019 study that near Greenland-with a large number of ice sheets-the warming cycle caused by the loss of sea ice has little effect on its warming, but has little effect on the ice sheet itself. Geophysical Research Letter.
Changes in sea ice may also affect seasonal weather and may exacerbate extreme weather. However, Rabe said that this issue needs further study. He said: “Scientists are actively studying the links between Arctic sea ice loss and winter climate patterns in North America, Europe and Asia.” “However, these relationships are still highly uncertain in the scientific literature and seasonal weather forecasts.”
For now, the plunging amount of sea ice is a surprising reminder of how fast the planet is changing and how terrible the consequences of delaying the complete reduction of greenhouse gas emissions will be.
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