Thwaites Glacier, one of Antarctica’s fastest melting glaciers, which has lost an estimated 595bn tonnes of ice since the 1980s contributing to a 4% rise in global sea levels, is back in the news. A robotic submarine has returned from the first-ever trip under the ice shelf with some alarming information. The glacier could be melting at the key points anchoring it to the land, faster than previously thought. Though the 192,000 sq km chunk of ice, nicknamed the “Doomsday Glacier,” in West Antarctica has been on climate scientists’ radars for two decades now, they did not know just how fast the glacier was melting.
The first measurements ever performed under Thwaites Glacier have revealed that a previously underestimated current of warm water is flowing from the east, whittling away at several vital “pinning points” that anchor the shelf to the land. “Our observations show warm water impinging from all sides on pinning points critical to ice-shelf stability, a scenario that may lead to unpinning and retreat,” the study authors wrote in the paper, published April 9 in the journal Scientific Advances. This means that the entire ice-shelf could get detached and then flow into the ocean.
Since Thwaites Glacier acts like a cork in a bottle, stopping the rest of the ice in the region from flowing into the sea, its collapse could potentially take the rest of the West Antarctic Ice Sheet with it, causing a 10ft rise in global sea levels. The worry is that this water is coming into direct contact with the underside of the ice shelf at the point where the ice tongue and shallow seafloor meet, according to study co-author Alastair Graham, associate professor of geological oceanography at the University of South Florida. “This is the last stronghold for Thwaites and once it unpins from the sea bed at its very front, there is nothing else for the ice shelf to hold onto. That warm water is also likely mixing in and around the grounding line, deep into the cavity, and that means the glacier is also being attacked at its feet where it is resting on solid rock,” Graham explained.
Located more than 1,600km away from the nearest research base, Thwaites is remote even by Antarctic standards. The submarine’s sonar also enabled high-resolution ocean mapping of the cavity floor, helping scientists to visualise the paths that currents take in and out. They spotted three main inflows of water. One, a deepwater flow from the east, was once assumed to be blocked by an underwater ridge, but the submarine data shows that the current is making its way into the bay. This means that currents are flowing into the glacier from both sides, possibly eroding it at its main anchoring point, located to the north.
Just how much melting is going on is not clear, but the researchers predict that just one of the currents alone is capable of reducing the ice at a rate of more than 85 gigatons per year. Exposure to warmer water could also push Thwaites’ neighbouring Pine Island Glacier past a tipping point, researchers showed in a study published March 25 in the Journal The Cryosphere. The Thwaites and Pine Island glaciers are currently responsible for 10% of the ongoing increase in global sea levels, according to the Cryosphere study, according to livescience.com
The only relief is that scientists are for the first time collecting data that is necessary to model the dynamics of Thwaites glacier, as study lead author Anna Wåhlin, professor of oceanography at the University of Gothenburg in Sweden, said. This data will help them better calculate ice melting in the future, improve the models and reduce the great uncertainty that now prevails around global sea level variations.
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