(ORDO NEWS) — The reason is probably natural variability, although global warming may play a role. This year, Antarctic sea ice has shrunk to less than 2 million square kilometers, the lowest since satellite records began 43 years ago.
The minimum area of 1.92 million square kilometers was recorded on February 25 and was 190,000 square kilometers less than the second minimum area reached in 2017, the US National Snow and Ice Data Center (NSIDC) said on March 8.
“The record low total Antarctic sea ice extent occurred in much the same way as in 2017,” says Ryan Vogt, a climatologist at Ohio University Athens. After 2017, sea ice extent remained well below average for several years before returning to near-average conditions in 2020.
The record low was partly due to strong winds that pushed ice out of the Ross Sea, an inlet off the coast of Antarctica, to more northerly regions where it is warmer. There, the ice broke and melted, says Walt Meyer, a senior fellow at NSIDC at the University of Colorado Boulder. “I think most, if not all, of this event can be attributed to natural variability,” Mayer says.
Unlike the Arctic, where sea ice has been shrinking rapidly since satellite measurements began in 1979, Antarctic sea ice varies greatly from year to year (see “Lowest Record”), contrary to the expectations of some climate models that predicted its decline in response to increasing greenhouse gas emissions.
The highest and second-lowest record minimums for Antarctic sea ice were reached in 2008 (3.69 million sq km) and 2013 (3.68 million sq km). In 2015 and 2016, the minimum dropped sharply. “With so much volatility, it’s not too surprising that a record low could be reached,” Mayer says.
In Antarctica, sea ice will grow wherever it is cold enough for ice to form. “There are no land barriers along the way,” Vogt says. Without barriers, the ice becomes much thinner, which means it can move freely under the influence of the winds, covering a larger area, he adds.
“Antarctic sea ice responds to the vagaries of the atmosphere and the ocean,” says Pat Langhorne, who studies the ice at the University of Otago in New Zealand. This includes wind direction and ocean tides, as well as patterns in the tropical Pacific associated with El Niño and La Niña.”
Meyer says that Antarctica’s isolation is keeping much of it warm so far, with the exception of the Antarctic Peninsula, which juts out to the north and has warmed noticeably over the past 40 years. Global warming could play a role in this new record, but it’s too early to tell, he says.
“This could be the start of a sustained loss of Antarctic ice, similar to what we’ve seen in the Arctic over the past 50 years, or it could be short-term variability that’s reverting back to the average year,” says Zeke Hausfather, a climate scientist at Berkeley Earth in California. In the long term, climate change will reduce Antarctic sea ice, he adds.
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