Tides undermine massive Thwaites Antarctic Glacier

High-resolution satellite radar data has shown the intrusion of warm, high-pressure seawater “many kilometers beneath the ice” of the giant Thwaites Glacier in Antarctica.

Vigorous melting

In a study published in Proceedings of the National Academy of Sciences ⁽¹⁾a team led by the University of California Irvine said widespread contact between ocean water and the glacier, a process replicated throughout Antarctica and in Greenland, causes “vigorous melting” and may require a reassessment of projections. global Rising sea levels.

The glaciologists relied on data collected from March to June 2023 by the Finnish commercial satellite mission ICEYE. ICEYE satellites form a “constellation” in polar orbit around the planet, using InSAR (Synthetic Aperture Interferometer Radar) to persistently monitor changes on the Earth’s surface. Many passes of a spacecraft over a defined small area produce smooth data results. In the case of this study, it showed the rise, fall and curvature of the Thwaites Glacier.

“This ICEYE data provided a series of daily observations that closely fit tidal cycles,” said senior author Eric Rignot, professor of earth system science at UC Irvine.

“In the past, we had some data available sporadically, and with just those few observations it was difficult to know what was happening. When we have a continuous time series and compare it to the tidal cycle, we see that seawater comes in at high tide and retreats and sometimes rises further under the glacier and gets trapped. Thanks to ICEYE, we are beginning to witness this tidal dynamic for the first time.”

Michael Wollersheim, director of analysis at ICEYT, said in a statement: “Until now, some of nature’s most dynamic processes have been impossible to observe in sufficient detail or frequency to allow us to understand and model them. Observing these processes from the space and the use of satellite radars, images, which provide InSAR measurements of centimeter level precision with a daily frequency, even up to three times a daymark an important advance.”

The project helped him better understand the behavior of seawater at the bottom of the Thwaites Glacier

Rignot said the project helped him and his colleagues better understand the behavior of seawater at the bottom of the Thwaites Glacier. He said that seawater reaching the base of the ice sheet, combined with the sweet water generated by geothermal flow and friction, it builds up and “has to flow somewhere.” Water is distributed through natural conduits or collected in cavities, creating enough pressure to lift the ice sheet.

Overlying ice pressure

“There are places where the water is almost at the pressure of the overlying ice, so you only need a little more pressure to push the ice up“Rignot said. “The water is then compressed enough to lift a column of more than half a mile of ice.”

Evidence of the impact of climate change on ocean currents, which push warmer seawater toward the coasts of Antarctica and other polar ice regions

AND It is not just any sea water. For decades, Rignot and his colleagues have been collecting evidence of the impact of climate change on ocean currents, which push warmer seawater toward the coasts of Antarctica and other polar ice regions.

Circumpolar deep water is salty and has a lower freezing point. While fresh water freezes at zero degrees Celsius, salt water freezes at minus two degrees, and that small difference is enough to contribute to the “vigorous melting” of basal ice as found in the study.

Co-author Christine Dowa professor at the School of Environment at the University of Waterloo in Ontario, Canada, said: “Thwaites is the most unstable place in Antarctica and contains the equivalent of 60 centimeters of sea level rise. The concern is that “we are “underestimating the speed at which the glacier is changing, which would be devastating for coastal communities around the world.”