Researchers can't make sense of surprising temperatures in Antarctica

Jim Yungel

It’s been a strange stretch for the icy desert at the bottom of the world.

In mid-March, temperatures in parts of East Antarctica soared 70 degrees Fahrenheit above average. It was high enough for researchers living there to brave the elements for a bare-chested group photo.

The comparably balmy temperatures, which reached around 10 degrees Fahrenheit, arrived courtesy of a history-making atmospheric river — a plume of concentrated moisture that flows through the sky. This one brought an incredible dump of snow in the inner reaches of the ice sheet, something quite rare for the area.

And in what could be a separate development, the Conger Ice Shelf — a hunk of ice similar in area to Los Angeles — collapsed into the sea right around the same time, satellite imaging shows.

Researchers are scrambling to make sense of what has happened. The surprising temperatures and moisture are already changing how they think about weather in Antarctica and raising questions about what impacts the continent could see if such a wild temperature swing had happened in summer — or in a warmer future.

And while researchers say it’s too early to know what role, if any, climate change is playing here, the event has their attention because it’s so extreme.

“It was something we didn’t think was possible in Antarctica, the magnitude of heat, especially in what should be the cold season in Antarctica,” said Jonathan Wille, a postdoctoral researcher at the Université Grenoble Alpes in France, of the heat wave. “We’ve never seen the atmosphere behave like this over Antarctica.”

The heat wave and dramatic inland snowfall highlight the importance of a better understanding of the complicated dynamics of atmospheric rivers — which today bolster the ice sheet but could be cause for concern in the future. Better grasping these patterns could be key to understanding the polar region’s future.

Having snowfall during a heat wave might sound counterintuitive, but this is Antarctica, after all, where inland winter temperatures routinely fall beneath 60 degrees below zero.

The recent atmospheric river event played out over several days. March 17 was the fourth-wettest day since 1980 for the ice sheet, according to modeling and analysis by Xavier Fettweis, a climatology professor at the University of Liège in Belgium.

A day later, temperatures at the Concordia station, a research station nearly 700 miles from the coast, spiked to a high of about 10 degrees Fahrenheit, stunning researchers.

“An extreme event of this magnitude has never been observed at Dome C,” said Peter Neff, a glaciologist, climate scientist and assistant research professor at the University of Minnesota, referring to the Concordia area.

Coastal temperatures rose above freezing levels, and rain pattered the coast. Intense snowfall across the interior of East Antarctica added an estimated 69 gigatons of water mass to the ice sheet, according to modeling by Fettweis. That’s the equivalent of nearly 28 million Olympic-size swimming pools of added water mass that came down in frozen form. That represents more than a third of the yearly ice loss in Antarctica.

“It added much more mass to the ice sheet than it took away,” Wille said. “Events like this, they help mitigate some of the sea level rise caused by climate change” by storing water as polar ice.

Such snowfall offers important protection, too.

Some Antarctic ice shelves — floating ice that clings to coastal Antarctica — are losing mass and at risk of collapse into the sea. Today, much of that risk comes from the ice melting from below, in warm water.

But in other polar regions, such as Greenland, ice shelves are melting from below — and also above — as surface temperatures rise, Neff said. Surface melt can create ponds of dense water that can more easily absorb heat, open crevasses and “jackhammer” downward until ice cleaves and collapses.

For sensitive parts of Antarctica, adding mass and a protective layer of hardening snow provides some cushion.

“Snowfall is a good thing, because it adds to this buffering layer on the surface of this ice sheet. The buffer can absorb more melt in the future,” said Michelle Maclennan, a doctoral student at the University of Colorado in Boulder, who has studied the effects of atmospheric rivers in West Antarctica and the vulnerable Thwaites Glacier. “As long as atmospheric rivers are causing a lot of snowfall and that snowfall is dominating impacts of surface melt, we’re going to see that they have this net positive effect on Antarctica.”

Often called rivers in the sky, atmospheric rivers aren’t uncommon in Antarctica.

Wille’s previous research suggests they’re responsible for about 10 to 20 percent of total snowfall across East Antarctica. West Antarctica can see anywhere from a handful to more than 10 events a year, Maclennan said.

These patterns originate in oceans and at warmer latitudes. “They’re like firehouses of moisture,” Neff said.

That firehose during mid-March was the strangest observed in Antarctica.

“Upper-level pressure values were like six standard deviations from the mean,” Wille said. Temperatures soared beyond what researchers thought was possible for this season. Moisture penetrated much deeper into the continent than usual.

The anomaly raises new questions. How these patterns act in the future could have significant consequences for ice shelves and for sea level rise across the globe.

Take the Thwaites Glacier, in West Antarctica. The Thwaites is losing ice at one of the fastest rates in the region and contributes to a few percentage points of global sea level rise each year, Maclennan said. That trend is driven by warm ocean water melting the bottom of the floating ice shelf, not surface melt. If the glacier were to collapse, it could precede as much as 10 feet of sea level rise over decades or centuries, according to Neff.

Today, atmospheric rivers help buffer the Thwaites by providing heavy snowfall that help protect the ice. Their impact outweighs any surface melt they cause, Maclennan said. But such an extreme event raises questions about what impacts these weather patterns could have in the future.

“If you had a serious atmospheric river hit that shelf, what would that do?” Neff wondered. “If this hit Thwaites Glacier in the middle of the summer, it would be consequential.”

Neff believes Thwaites could absorb such a “punch” today, but also believes the glacier could be more vulnerable later this century as the climate warms.

Said Maclennan: “It’s hard to judge what the impacts might be, but this event does really challenge us to change our understanding of what the range of extremes has been.”

The issue requires more study. Scientists only began to focus on atmospheric rivers in Antarctica around 2013.

In Antarctica, it can be difficult to know what’s normal or expected. Temperatures can seesaw wildly, the continent has relatively few weather stations and satellite observations only stretch back about 40 years.

“The classic problem in Antarctica — everything is stacked against you to be able to put anything in context,” Neff said.

The fingerprint of climate change hasn’t emerged clearly in this region as it has elsewhere in the world.

Was the heat wave a new signal of its impacts? Researchers don’t know yet.

“This does fit into a broader pattern we’re seeing of these extreme weather events that break our notion of what we think could happen in our climate system,” Wille said, comparing the event’s surprising nature to the 2021 flooding in Germany and the heat dome in the Pacific Northwest that shattered temperature records. “Was this event caused by climate change or influenced by climate change? We have to study that.”

Wille said it’s possible that this type of weather could be something to be expected rarely — say once every 100 years — regardless of climate change. It’s possible researchers haven’t been measuring Antarctic weather trends long enough to witness an anomaly like this before, he said.

Neff — who drills and analyzes ice cores to puzzle out evidence of past climates — said those cores could one day provide some answers.

In the weeks leading up to the heat wave, the Conger Ice Shelf in East Antarctica began to break apart.

Sometime around March 15, near the time the heat wave began to ramp up, the ice shelf collapsed entirely, sending icebergs floating into the sea.

“East Antarctica is starting to change. There is mass loss starting to happen,” Helen Amanda Fricker, a co-director of the Scripps Polar Center at the University of California San Diego, told The Associated Press.

“We need to know how stable each one of the ice shelves are because once one disappears” it means glaciers melt into the warming water and “some of that water will come to San Diego and elsewhere.”

The collapse was “teeny tiny” by Antarctic standards and unlikely to have substantial impacts, Neff wrote in a message. But such events are rare in East Antarctica, which is generally more stable, he said. It’s not clear if the atmospheric river and its heat are linked to the collapse.

Still, it’s another odd episode in a season of strange twists and turns.

“We can’t sleep on East Antarctica thinking it’s a static big ice cube,” Neff wrote. The collapse “makes us think, just like the atmospheric river.”