Narrow corridors of air loaded with moisture straight from the tropics may be driving a series of ice shelf collapses in the fastest-warming part of Antarctica, scientists have found.
Why it matters: Ice shelves act like doorstops, holding back the land-based ice behind them. When they are lost or weakened, inland ice can melt faster, raising sea levels worldwide.
Driving the news: A new study, published Thursday in the journal Communications Earth and Environment, ties together for the first time developments in the upper atmosphere, on the ice and in the sea that may be priming large ice shelves in the Antarctic Peninsula for headline-grabbing disintegrations.
- The study warns such weather phenomena, acting in concert with long-term human-driven global warming, may cause the next big ice shelf, known as Larsen C, to collapse.
- Scientists have been monitoring the Larsen C Ice Shelf especially closely since a massive calving event in 2017 broke off one of the largest icebergs on record, leaving the shelf and the ice it holds back in a weakened state.
Threat level: The study found that 60% of calving events from ice shelves in the Antarctic Peninsula had atmospheric rivers as a trigger.
- Such events, which transport huge quantities of water vapor and heat from the tropics and sub-tropics toward the poles, can act as a compound extreme event for ice shelves, the study finds.
- In the Antarctic Peninsula, the study finds, atmospheric rivers can cause air to flow downhill from mountain slopes, compressing and warming in the process.
- These "foehn winds" are known to lead to sudden spikes in surface temperatures, and helped yield the highest temperature on record for the continent, at 65°F, set at Spain's Esperanza Station in 2020.
Between the lines: Warmer temperatures and rainfall associated with atmospheric rivers can also cause surface melt that weakens ice from the top down.
- By scattering protective sea ice, storms associated with atmospheric rivers can allow large waves to reach the main portion of an ice shelf, battering the ice.
Context: The study, which used satellite imagery and other techniques to detect atmospheric rivers and monitor ice activity, in addition to computer simulations, found that multiple atmospheric river events preceded the collapse of the Larsen B Ice Shelf in the austral summer of 2002.
- The collapse of Larsen B was the inspiration for the opening scene in the 2004 global warming disaster blockbuster, "The Day After Tomorrow."
- Likewise, in 1995 another atmospheric river, this one unusually intense, came just before the collapse of Larsen A.
What they're saying: "The Larsen C Ice Shelf is still there, but we believe all of the same processes we observed for the Larsen A and Larsen B will also affect the Larsen C ice shelf and prove a risk," lead author Jonathan Wille of Université Grenoble Alpes in France in France, told Axios in an interview.
- Wille said Larsen C has been located in a cooler spot, farther south, compared to Larsen A and B. However, this is changing as the climate warms.
- "A warming climate makes these atmospheric rivers more of a risk factor for the stability of the Larsen C," he said.
Yes, but: The study cautions that there are unknown factors that go into prompting a massive ice shelf to collapse, likely beyond a series of short-term events.
- Helen Fricker, a climate researcher at the Scripps Institution of Oceanography who was not involved in the new study, said atmospheric river events aren't currently incorporated into predictions of Antarctica's future.
- "We need to understand the processes driving mass loss from the ice shelves at high spatial and temporal resolution so we can build up sufficient knowledge of these processes to model them," she told Axios via email.
