Sea ice over Antarctica just shrank to its smallest extent on record

Antarctic sea ice recently reached its lowest concentration on record - falling below 2 million square kilometers (772,000 square miles) for the first time in 43 years of satellite observations.

"It's the first time on satellite record that we've had sea ice extent fall below 2 million square kilometers. It's a record and by quite a bit," said Ryan Fogt, a climate scientist and professor at Ohio University.

Sea ice builds and melts with the seasons. In Antarctica, sea ice typically reaches its maximum coverage at the end of the austral winter in mid- to late- September and melts to its minimum extent in February.

The 2021-2022 melt-and-freeze cycle has been a bit unusual, however. Antarctic sea ice reached its maximum extent on Sept. 1, 2021, almost a month earlier than normal peak. The sea ice maximum extent, measuring 18.75 million square kilometers (7.24 million square miles), was also well above average. But it didn't last long.

Sea ice retreated rapidly through austral spring and summer. In January and February, ice cleared out from the Ross, Amundsen and northwestern Weddell Sea regions. According to the National Snow and Ice Data Center (NSIDC), Antarctic sea ice reached its minimum extent of 1.92 million square kilometers on February 25. The previous low occurred in 2017 when sea ice extent reached 2.11 million square kilometers (815,000 square miles).

"It's a record low, but we see a lot of year-to-year variability. One year is a little bit higher, one year is a little bit lower," said Walt Meier, a research scientist at NSIDC. "There's really no trend."

Meier said the yearly fluctuations can be partly explained by geography. "The Antarctic is open to the ocean so it's very susceptible to changes and circulation changes in the ocean currents . . . The ice is thin, it moves around with the wind currents, it's very variable. Even subtle changes can make a pretty big difference," said Meier, based at the University of Colorado Boulder.

Even though human population is sparse on the continent, the low sea ice has effects on researchers and wildlife living on the continent.

"In places like the Ross Sea that doesn't have much sea ice this year, penguins are going to be on the coasts and there's going to be seals right near the coasts," said Fogt.

Fogt also said supply ships bringing fuel and food had an easier time reaching some U.S. bases. Near Pine Island Bay though, the higher sea ice concentrations near the Thwaites Glacier blocked access to researchers, forcing them to conduct their research on the Dotson Ice shelf to the west instead.

Despite the new low, researchers are cautious to attribute the low sea ice concentrations to climate change. In fact, research and data suggest Antarctic sea ice concentrations naturally fluctuated over the past 150 years.

In a recent study, Fogt and his colleagues reconstructed Antarctic sea ice concentrations back to 1905 using statistical models. They found sea ice was on the decline in the 20th century but then increased after 1979.

"It's very likely that what we're seeing now is within the range of variability that we've seen over the last century. So even this record low, we probably have seen that before in the last century," said Fogt. "What we're seeing is just year to year fluctuations that have happened in the longer-term context."

Since 2016, sea ice concentrations have been on a slight downward trend. Including 2022, the summer minimum for the past seven years has been below the 1980-2010 average, but any long-term trend is still statistically insignificant said the National Oceanic and Atmospheric Administration.

"If we see this going on for another five years where we have record low or near record lows, then maybe we can start thinking about is it responding [to warming]," said Meier. "I would be very hesitant at this time to infer anything about a response to global warming."

While ties between Antarctic sea ice extent and climate change are unclear, increasing greenhouse gas emissions are affecting other aspects of our polar regions. Both Antarctica and the Arctic are warming faster than the global average. Human-caused global warming has led to both the Antarctic and Greenland Ice Sheets to lose significant amounts of land ice. Warm ocean temperatures threaten to destabilize Antarctica's Thwaites Glacier, a slab the size of Florida that already contributes about 4% of annual global sea level rise.

On Wednesday, temperatures near the North Pole were about 50 degrees (28 Celsius) above normal - an example of abnormal warm spells becoming more frequent in a warming world. Meier detected a crack forming in the ice on the northeast coast of Greenland from satellite data, likely tied to the pulse of warm air. He expects the surface to refreeze once the system passes though before Greenland melt season, which has become more intense in recent decades due to the warmer climate.

The Vostok weather station, located in the middle of the East Antarctic Ice Sheet and home to the world record low temperature of minus-126.9 degrees (minus-88.3 Celsius), hit 0 degrees (minus-17.7 Celsius), its highest March temperature - surpassing its previous record for the month by about 27 degrees (15 Celsius). Its average March high is closer to minus-60.

"This is a Pacific Northwest 2021 heat wave kind of event," tweeted Jonathan Willie, a researcher studying polar meteorology at Université Grenoble Alpes in France. "Never supposed to happen."

- - -