Antarctic sea ice is melting to a new record low for the second year in a row
For the second year in a row, summer sea ice around Antarctica has reached a new record low.
In February 2022, satellites recorded the lowest sea ice extent ever observed in Antarctica in summer.
“For the first time since satellite recording began in 1979, the extent fell below two million square kilometers, reaching a minimum extent of 1.92 million square kilometers on February 25,” said the US National Snow and Ice Data Center (NSIDC). Time.
Now, less than a year later, not only has the extent fallen back below two million square kilometers, but it has surpassed the record minimum set in 2022.
On February 14, 2023, the extent shrank to less than 1.9 million square kilometers.
This chart shows the extent of Antarctic sea ice from 1979 to 2022 and so far in 2023. The inset is a magnified view of the late summer minimums comparing the 1.875 million square km extent on February 15, 2023 to the previous record low February 25, 2022 (Jan .92 million square kilometers). The panel to the right shows how sea ice extent had fallen below historical lows as early as December 23, 2022, and has remained at low levels to date. (NSIDC/Scott Sutherland)
“This year marks only the second year that Antarctica’s extent has fallen below two million square kilometers,” the NSIDC said in its Feb. 13 update.
Based on the usual melting pattern, we haven’t even seen the new final record low yet.
“With likely a few more weeks left in the melting season, magnitudes are expected to decrease further before reaching their annual minimum,” the NSIDC said.
As shown in the chart above, sea ice extent around Antarctica fell below previous record lows in December, and this trend has continued through January and February so far.
NSIDC scientists attribute this to weather conditions, specifically stronger than average westerly winds and a strong low-pressure system over the Amundsen Sea, resulting in warmer weather hitting a large region of West Antarctica.
“Even as someone who’s been looking at these changing systems for a few decades, I was surprised by what I saw, by the level of warming I saw,” Carlos Moffat, an oceanographer at the University of Delaware, told Inside Climate News.
According to ICN, Moffat was part of a recent expedition along the coast of West Antarctica, where researchers found “an eerily warm ocean and record-breakingly low sea ice coverage.”
“We don’t know how much longer this will last,” Moffat said. “We don’t fully understand the implications of this type of event, but this looks like an extraordinary marine heatwave.”
The extent and concentration of Antarctic sea ice on February 16, 2023 compared to the 30-year average extent (yellow line). While sea ice is near average along East Antarctica and in the Weddell Sea, there is little ice compared to normal along West Antarctica. (NSIDC)
coastal defenses lost
One benefit of having more sea ice around Antarctica is that it tends to act as a buffer for coastal glaciers, keeping the warmer ocean water farther out to sea and calming the waves at the ice’s edges.
According to the NSIDC, at this record low in sea ice extent, “much of the Antarctic coast is ice-free, exposing the ice shelves that line the ice sheet to wave action and warmer conditions.”
One of the glaciers exposed by this lack of ice is Thwaites, West Antarctica’s Doomsday Glacier, aptly named Doomsday Glacier.
Researchers have shown that Thwaites is retreating rapidly by about a kilometer each year, and one estimate suggested the entire glacier could collapse within five years.
These maps show the position of Thwaites Glacier, which is pinned between the West Antarctic Ice Sheet and the Amundsen Sea. (NASA)
With the coast being more exposed to warm ocean waters, glaciers like Thwaites are even more at risk. New research examined the impact these warmer waters may have on Thwaites, specifically by sending a diving robot under the glacier to observe how the ice is being affected from below.
“These new ways of observing glaciers allow us to understand that in these very warm parts of Antarctica, it’s not just how much melting is important, but how and where it’s happening,” says Britney Schmidt, lead author of the Cornell University paper. said the Cornell Chronicle. “We see crevasses and probably terraces over warming glaciers like Thwaites. Warm water seeps into the cracks and helps wear down the glacier at its weakest points.”
See below: Underwater robot helps explain Antarctic glacier retreat
A complete collapse of Thwaites would directly cause global sea levels to rise by more than 60 centimeters. More importantly, the glacier is currently holding back much of the West Antarctic Ice Sheet. For example, the collapse of Thwaites could rapidly destabilize the ice sheet behind it, which could raise sea levels by another ten feet or more.
A new alarming trend?
The sea ice around Antarctica goes through a seasonal growth and melting cycle. The ice reaches its maximum extent in September, during the late southern winter. Then the melting season begins, which is minimal in late summer in late February or early March. The curve that ice extent follows varies from year to year based on weather conditions. However, some trends can be observed in recent decades.
Shown here is the minimum extent of Antarctic sea ice for each year from 1979 to 2022. The current lowest point, in 2023, is the smallest extent observed since records began. (NSIDC)
There was a slight but noticeable downward trend until the early 1990s. From the mid-1990s, the overall extent of Antarctic sea ice began to increase—both winter maxima and summer minima. But in the last eight years, that trend seems to have reversed.
Experts attribute the increase from the 1990s to the mid-2010s to two main factors: More ice formed because more meltwater flowed from land ice into the oceans, and stronger winds spread the sea ice mass further into the ocean. This trend was aided by a strong southern polar vortex flowing over Antarctica, coupled with a strong ocean current circulating around the edges of the Southern Ocean, both of which protected the region from much of the climate change impacts felt in the rest of the world were felt.
However, it was not to be expected that this trend would continue. Rising sea and air temperatures would inevitably take their toll and reduce sea ice extent. Since 2016, we seem to be seeing this reversal now.