Deep channels under Antarctic glacier may increase melting rate
The Thwaites Glacier and its tongue in West Antarctica have received massive scientific interest due to the amount and speed at which the ice masses retreat. A large-scale British-American expedition has searched for and probably discovered the reasons for the accelerated speed of the Thwaites ice melt: Deep channels in the seabed under the glacier tongue allow warm deep water to flow far inland below the glacier.
“It was fantastic to be able to map the channels and cavity system hidden beneath the ice shelf.”
Dr Tom Jordan, British Antarctic Survey
Back in February, researchers at the ITGC (International Thwaites Glacier Collaboration) reported that warm water are melting the glacier from three sides. But the results now published show how far the warm water can penetrate below the glacier. And the result also left the experts amazed. Channels up to 800 metres deep penetrate inland up to 60 kilometres below the icy giant to the grounding line and cause the ice to melt through slightly warmer water masses. “It was fantastic to be able to map the channels and cavity system hidden beneath the ice shelf,” explains Dr Tom Jordan of the British Antarctic Survey. “They (the channels) are deeper than expected – some are more than 800 metres deep. They form the critical link between the ocean and the glacier.” Dr. Jordan led the aerial measurements using a Twin Otter machine of the BAS.
In addition to aerial photographs and measurements, another team aboard the American icebreaker Nathaniel B. Palmer was able to reach the edge of the glacier and accurately map the seabed in front of it. As a result, the researchers discovered that the sea floor was much deeper than previously thought and rugged by the deep channels that lead to the glacier’s grounding line, where the ice touches the seabed. ” For the first time we have a clear view of the pathways along which warm water can reach the underside of the glacier, causing it to melt and contribute to global sea-level rise,” explains Dr. Kelly Hogan of the BAS, who was on board the ship as part of the research team. Both teams have published their findings in the latest issue of the journal The Cryosphere.
The latest findings from the ITGC team now provide a partial answer to the question of why over the past 30 years, Thwaites Glacier has experienced rapid mass loss. Researchers have calculated that the Thwaites glacier and its tributaries accounted for about 50-55 percent of the mass loss of the West Antarctic ice sheet. While between 1979 and 1989 the mass loss was about 4.6 gigatons of ice per year, the amount had increased eightfold between 2009 and 2017 to 34.9 gigatons. The ITGC research teams, which also come from Sweden, Germany and South Korea, not only search for the reasons behind this increase in speed, but also the impact on sea level rise and how quickly and how much the pace of losses will change in the future. The project, which was launched in 2018, is expected to continue until 2023.
Dr Michael Wenger, PolarJournal
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