A confluence of warm water threatens to topple the pillars that keep the Doomsday Glacier afloat.
The first measurements ever taken under the icy tongue of Antarctica’s Thwaites Glacier have now revealed a previously underestimated stream of warm water from the east.
This influx of heat mixes with other water beneath the glacier and pushes several critical “ tie points, ” say researchers, pulling them down from all sides.
If activity continues or, worse, accelerates, the team fears it could eventually dislodge large amounts of land ice flowing from the seafloor to Pine Island Bay.
The Thwaites Glacier has been nicknamed the Doomsday Glacier because it is so large – at 192,000 square kilometers (74,000 square miles), slightly smaller than the state of Kansas in the US – and is melting at a nerve-racking pace. As a result, the future of the West Antarctic Ice Sheet remains the biggest point of uncertainty for sea level rise.
Due to the remoteness of the glacier and the hazardous conditions in the region, only a few measurements have been taken near the edge of the ice shelf, and none have been in the cavity below it until now.
“The good news is that, for the first time, we are collecting data needed to model the dynamics of the Thwaite Glacier,” said physical oceanographer Anna Wåhlin of the University of Gothenburg in Sweden.
“With this data we can better calculate future ice melting. With the help of new technology, we can improve the models and reduce the great uncertainty that now exists around global sea level variations.”
The information was gathered by an underwater vehicle called Ran, which swam deep under the thick ice to measure the strength, temperature, salinity, and oxygen content of the underlying ocean currents.
The trip was more successful than scientists had hoped, but the results were not as promising.
Right now, the Thwaites Glacier makes up about 10 percent of current sea-level rise, but because warm and salty waters tend to converge beneath it, the ice shelf has the potential to contribute much, much more as the planet warms. Like removing a cork from a wine bottle, the loss of this ice shelf can cause even more ice to melt on land and flow into the ocean.
Ultimately, researchers identified three inflows of warm water, one of which we had seriously underestimated. Deep water currents from the east were thought to be blocked by an underwater ridge nearby, but Ran’s new data suggests these deep currents are still making their way into the bay.
“The channels for hot water to reach and attack Thwaites were unknown to us before the study,” said geological oceanographer Alastair Graham of the University of Southern Florida.
“Using on-ship sonars nested with Ran’s very high-resolution ocean maps, we were able to discover that there are several paths that take water in and out of the ice shelf cavity, influenced by the geometry of the ocean floor.”
Ultimately, this means that warm, salty waters enter the hollow below the Thwaites Ice Shelf from both sides of the main fixation point in the north, potentially destabilizing the entire structure.
It is still unclear how much of that available heat actually contributes to the melting of this main pin point, but the authors predict that the energy transported by just one local current is enough to melt the above ice at a rate of more than 86,000 kilograms (about 95 tons). per year.
That corresponds to the total basal melt of the entire Thwaites Ice Shelf between 2010 and 2018, indicating that this warm influx is likely to affect the melting pattern of the entire system.
“This lock point is one of the last supporting features to hold back the ice flow from upstream, and satellite observations indicate that its size has declined over the past few decades,” the authors write.
The ominous day of the world may come sooner than we thought.
The study is published in Science Advances