Study: Daily Tidal Action Makes Thwaites Glacier More Vulnerable Than Thought To Melting From Underneath

Daily tides bring warm ocean water farther in beneath West Antarctica’s Thwaites Glacier than previously thought, potentially causing ice to melt faster than expected, according to a new study. The finding could help scientists make better predictions about the fate of one of the world’s most closely watched glaciers. Thwaites, known as the “Doomsday Glacier,” is about the size of Florida. It currently contributes about 4% to global annual sea level rise.

Most ice sheet simulations have not accurately predicted Thwaites’s recent retreat because they assume that a glacier’s grounding line is fixed. But recent research on Thwaites and other glaciers has shown that these boundaries between floating ice and ice that is grounded on the seafloor shift with the daily tide. Glaciers are heavily crevassed above their grounding lines, so studying them from the top of the ice is dangerous. Satellite data can help scientists illuminate the glacier’s underbelly from high above, but most satellites pass over a given spot only once every few days. That’s not enough resolution to work out how tides contribute to the daily movement of the grounding line.

Using satellite radar data from the private company ICEYE collected over 3 months in 2023, a team of glaciologists created a detailed image of Thwaites’s shifting grounding line by looking at how the glacier surface bobbed up and down throughout the day. "The difference with this study is that they were having multiple measurements per day,” said Alex Brisbourne, a glaciologist at the British Antarctic Survey who was not involved with the research. “So what they could see [were] these really short-timescale processes.”

Satellites can see only the surface of the ice, but because the ice is compacted, tiny vertical movements signal that the glacier bed must be rising too, wrote Eric Rignot in an email. Rignot is a glaciologist at the University of California, Irvine, and NASA’s Jet Propulsion Laboratory and first author of the study. The team found that the ice rose and sank in sync with the tides. The data suggested that the grounding line migrated up to 6 kilometers (3.7 miles) inland during an average high tide.

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https://eos.org/articles/radar-data-show-thwaites-gets-a-daily-bath-of-warm-seawater