Deep channels under Antarctic glacier may increase melting rate | Polarjournal
Thwaites Glacier is one the largest catchment area of glaciers on the west side of Antarctica. The ice surface, which covers an estimated 192,000 square kilometres, has contributed significantly to the current sea level rise and continues to melt at a rapid rate. Picture: David Vaughan via courtesy of BAS

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.

The American icebreaker Nathaniel B. Palmer was able to go close to the glacier tongue thanks to an extraordinary break-up of the sea ice in front of the glacier tongue, thus allowing to map more than 2,000 square kilometers of seabed in front of the glacier. Picture: Alex Mazur via courtesy of 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.

Perspective 3D view overlooking seabed canals towards Thwaites Glacier, West Antarctica. 3D perspective view looking along seafloor channels towards Thwaites Glacier, West Antarctica. The channels extend 30-60 km beneath the floating ice shelf to the grounding line and and may act as pathways for warm ocean water to reach the glacier. The water depth from sea level to the base of the channels is 800 to 1300 m. Graphic: courtesy of the BAS

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.

The video shows the measurement flights with the BAS Twin Otter over the Thwaites Glacier and the Glacier Tongue as part of the ITGC project. Duration: 2:31 min, Language: English. Video: courtesy of BAS

Dr Michael Wenger, PolarJournal

Link to the scientific articles:

Hogan et al. (2020) The Cryosphere 14 (9), Revealing the former bed of Thwaites Glacier using sea-floor bathymetry: implications for warm-water routing and bed controls on ice flow and buttressing

Jordan et al. (2020) The Cryosphere 14 (9), New gravity-derived bathymetry for the Thwaites, Crosson, and Dotson ice shelves revealing two ice shelf populations

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