A confluence of warm water threatens to overturn even the pillars that keep the “Doomsday Glacier” afloat.
The first measurements ever made under the frozen tongue of the Thwaites Glacier in Antarctica have now revealed a previously underestimated flow of hot water from the east.
This heat flux mixes with other water beneath the glacier and enters several critical “fixing points,” say researchers, reducing them on all sides.
If activity continues or, worse, accelerates, the team is worried that it could eventually detach massive amounts of land-borne ice flowing into the Pine Bay from the bottom of the sea below.
The Thwaites Glacier has been nicknamed the Doomsday Glacier because it is very large – at 192,000 square kilometers (74,000 square miles), slightly smaller than the US state of Kansas – and is melting at an annoying rate. As a result, the future of the West Antarctic ice sheet remains the biggest point of uncertainty for sea level rise.
Due to the remote location of the glacier and the dangerous conditions in the region, only a few measurements have been taken near the edge of the ice shelf and so far none have been made in the cavity below.
“The good news is that now, for the first time, we are collecting data needed to model the dynamics of the Thwaite Glacier,” says physical oceanographer Anna Wåhlin of the University of Gothenburg in Sweden.
“This data will help us better calculate ice melting in the future. With the help of new technologies, we can improve models and reduce the great uncertainty that now prevails around global sea level fluctuations.”
The information was collected by a submersible vehicle called Ran, which swam deep under thick ice to measure the strength, temperature, salinity and oxygen content of the underlying ocean currents.
The trip was more successful than the scientists hoped, but the results were not so promising.
Right now, the Thwaites Glacier accounts for about 10% of current sea level rise, but because warm, 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 bottle of wine, losing this ice shelf could cause more ice to melt and flow into the ocean.
Finally, three hot water streams were identified by researchers, one of which I was seriously underestimated. Deep water flows from the east are thought to be blocked by a nearby underwater ridge, but new data from Ran suggest that these deep currents are still making their way into the gulf.
“The channels for access to hot water and the attack on Thwaites were not known to us before the research,” says geological oceanographer Alastair Graham of the University of South Florida.
“Using sonar on the ship, nestled with the very high-resolution mapping of the ocean at Ran, we could see that there are distinct paths that water enters and leaves the ice shelf cavity, influenced by the geometry of the ocean floor.”
Finally, this means that warm, salty water enters the cavity below the Thwaites ice shelf on both sides of its main northern anchorage, possibly destabilizing the entire structure.
It is not yet clear how much of the available heat actually contributes to the melting of this main fixation point, but the authors predict that the energy carried by a single local current is sufficient to melt the ice above at a rate of over 86,000 kilograms ( about 95 tons) per year.
This is equivalent to the total basal melting of the entire Thwaites ice shelf between 2010 and 2018, indicating that these hot flows are likely to affect the melting pattern of the entire system.
“This anchorage is one of the last supporting features that prevents the flow of ice upstream, and satellite observations indicate that its extent has declined in recent decades,” the authors write.
World Doomsday could come sooner than I thought.
The study was published in Scientific advances.