As climate change continues to increase global temperatures, scientists are focusing on the most sparsely populated continent on the planet: Antarctica. The largely frozen southern continent has an immense amount of land ice that is gradually melting, causing sea levels to rise all over the world. A recent study revealed the so-called "doomsday" glacier, actually called Thwaites Glacier, began to lose large amounts of ice in the 1940s and is still melting today. If Thwaites collapses entirely, it would cause a domino effect of other melt events that could ultimately increase sea levels by 10 feet (3 meters). Even if global temperatures rise by 2°C or more above pre-industrial levels, as appears highly likely without major economic and social change, the resulting Antarctic melt could cause global sea levels to rise by as much as 6.6 feet (2 meters) by 2100.
Now there is more bad news from Antarctica: Scientists publishing in the Journal of Climate report that a "record-shattering" heat wave which struck East Antarctica in March 2022 was powered by the most extreme "atmospheric river" ever observed in the region, a freakish occurrence tied to climate change.
Atmospheric rivers are concentrated bands of water vapor from the tropics and subtropics, which on this occasion transported heat and moisture into the Antarctic interior. These have become more frequent as Earth's average temperatures continue to warm, especially with climate change increasing tropical cyclone activity and convection in the Indian Ocean. Even so, the atmospheric river that occurred in East Antarctica was still bizarre by modern standards. Concordia Station, a French-Italian research institute, recorded temperatures that were above average by 30° to 40°C, peaking at -9.4°C or 15°F. While that would be considered very cold in most of the world, it was several degrees warmer than the previous all-time high at that station. Essentially, the atmospheric river brought thick cloud cover that trapped heat in the lower atmosphere and, mixed with solar radiation, caused unusually warm temperatures at ground level.
That bad news was somewhat mitigated by a related fact: The atmospheric river also triggered high levels of snowfall, adding mass to the Antarctic ice sheet. There is no reason to believe that future warming events in the Antarctic will always be accompanied by increased snowfall, though, and the March 2022 event led to widespread surface melt in coastal areas while worsening the record-low extent of sea ice.
Heat waves like the March 2022 event in East Antarctica "are expected to become more frequent in [a] warming climate," says Dr. Jonathan D. Wille, postdoctoral researcher for the Climate Physics Group at the Institute for Atmospheric and Climate Science and co-author of the paper. Scientists now understand, he said, that "tropical weather patterns can cause extreme weather events in Antarctica that are far more intense than we have ever observed. It readjusted our view on what is physically possible for heat wave and atmospheric river intensity in Antarctica."
While the March 2022 heat wave only lasted four days, Wille said it had far-reaching consequences, demonstrating that "singular, short-lived weather extremes can have multifaceted long-lasting impacts on the Antarctic climate system ranging from ice mass increases in the interior [to] coastal surface melting, ice-shelf collapse, and affecting the way we measure the past climate from ice cores and cosmic-ray measurements."
Dr. Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research who was not involved in the study, said that as Antarctic heat waves impact other areas of the world by causing sea levels to rise, they will also accelerate melting processes and destabilize areas that hold glacier flow in check, leading to icebergs that melt more quickly. The unanswered question, Trenberth said, "is whether the atmospheric river took enough moisture into the continent to increase snowfall which offsets sea-level rise."
Dr. Michael E. Mann, a climate scientist at the University of Pennsylvania who also was not involved in the study, said it was consistent with other research demonstrating that climate change is causing unprecedented heat waves all over the planet. "It establishes the importance of changes in atmospheric circulation and the important and subtle role that they can play with some of these unprecedented weather extremes we’re seeing," he said.
"Our own research suggests that persistent summer weather extremes, such as heat waves, are becoming more common in a way that is now fully captured by current-day climate models, so what we’re already seeing there is worse than expected," Mann says. "It will get worse as long as we continue to warm the planet with carbon pollution."
The paper itself notes that although this Antarctic heat wave was a singular, record-breaking event, warming global temperatures makes it likely that these types of "record-shattering" events will become commonplace.
"This heat wave redefined our expectations of the Antarctic climate," the authors write. "Despite the rare chance of occurrence based on past climate, a future temperature-extreme event of similar magnitude is possible, especially given anthropogenic climate change."
