Thwaites Glacier. Photo: Stuart Rankin, NASA/James Yungel

West Antarctica’s glaciers are the weakest link in the icy armor that surrounds the massive southern ice sheet. A study published in the Annals of Glaciology last month adds to the pile of crap news about how these glaciers, which extend out over water that’s being warmed by climate change, are susceptible to melting that could screw the world’s coasts.

Scientists used a new technique to see how far water is intruding under West Antarctica’s Pine Island and Thwaites glaciers, two of the biggest and most vulnerable glaciers on Earth. They found signs that ocean water is pushing miles deeper under the ice than we realized in near a location where both glaciers meet, raising some uncomfortable prospects about how their futures could be intertwined.

The key to understanding West Antarctica’s fate is knowing where rock, water, and ice meet. That area is known as the grounding line. Warm waters have been eating away at ice from below in this region, and once grounding lines retreat far enough inland, entire glaciers can become unstable and collapse. That in turn means all the land ice will have nothing to stop it from sliding into the ocean and raising sea levels more than 10 feet.

“These are two of the largest and most rapidly changing glaciers in Antarctica, so the potential for their evolution to influence each other is important to consider in modeling ice sheet behavior and projecting future sea level rise,” Dustin Schroeder, a Stanford geophysicist who led the study, told Earther.

Satellites have provided grounding lines observations of Pine Island Thwaites glaciers (and other glaciers for that matter) since getting direct observations under the ice is basically a non-starter. But the new study relies on plane-based radar from three flights between 2004 and 2014. This is the first time two different types of radar observations have been combined for this type of analysis.

Advertisement

The results provide an intimate view of an area where Pine Island and Thwaites meet, and they paint a different picture than what satellites have shown us.

“One of the most powerful tools we have for observing ice sheet behavior and evolution is satellite remote sensing,”Schroeder said. “This point here is that ocean water is accessing further inland than we’d assume from those satellite measurements.”

Specifically, the new plane-based measurements show warm water is reaching nearly 7.5 miles inland from where satellite estimates indicate the grounding line on Pine Island Glacier’s southwest tributary to be. That means that either the water is finding a way to get up under the ice, or the grounding line has moved inland from what had been a relatively stable location from 1992 until 2011.

Advertisement

Neither is good news in a region where the two vulnerable glaciers essentially meet. The big questions now are how important the warm water invasion is, and if the fate of these two glaciers will be tied together by it.

“The study is unique in taking observations by different instruments and different field campaigns separated by a decade to document that changes in the region include the flow connecting these two outlets,” Charles Jackson, a geophysicist at the University of Texas who wasn’t part of the study, told Earther. “We don’t yet know whether that connection is significant. We mostly assume these two systems operate independently. However, when the stakes are as high as they are, every detail is potentially revealing.”

Now that the work has been done to combine these airborne measurements, Schroeder said he plans to expand this type analysis to other glaciers, a move that could improve scientists’ understanding of the hidden ways climate change is affecting ice.