A recent study published in the Proceedings of the National Academy of Sciences of the United States of America revealed that ocean tides are "punching holes" beneath the Thwaites Glacier in Antarctica, causing the thick ice sheet to melt from below. Satellite data indicates that the melting of the Thwaites Glacier may be much faster than previously thought.
David Holland, an oceanographer at New York University who was not involved in the study, noted the novelty of incorporating ocean tides into the research, stating that "tides are indeed changing the way glaciers melt."
The Thwaites Glacier is a crucial component of the Antarctic ice sheet system. Studies suggest that its collapse could raise global sea levels by over half a meter, earning it the moniker "Doomsday Glacier."
Located on bedrock that slopes inland deep into a basin in southwestern Antarctica, the Thwaites Glacier's vulnerable underside is susceptible to the influence of relatively warm ocean water, causing it to gradually melt and detach from the bedrock, flowing into the ocean.
Given that other glaciers in southwestern Antarctica also feed into the same basin, scientists believe that the melting of the Thwaites Glacier could accelerate the collapse of other glaciers, potentially leading to a sea level rise exceeding 3 meters over the coming centuries.
As early as 2021, researchers had observed cracks on the floating ice shelf beneath the glacier, indicating potential fracturing. However, the remote and thick ice layers of the Thwaites Glacier have hindered scientists from closely examining it using sampling, sensors, or subsea tools.
In a new study led by glaciologist Eric Rignot from the University of California, Irvine, scientists utilized satellite data and radar interferometry techniques. Analyzing radar data collected by the ICEYE satellite, they discovered that the Thwaites Glacier moves up and down by several centimeters every few hours, suggesting immense water pressure from below is "buoying" the glacier. The grounding line, where the glacier separates from the land and begins to float, also oscillates in sync with the advance and retreat of ocean tides. The grounding line, rather than being a specific line, is an approximately 200-square-kilometer convergence zone where the intrusion of the ocean is steadily widening, making the glacier more sensitive to seawater erosion.
Data further reveals that at times, seawater can intrude inland beneath the ice well beyond the grounding line. During high tides, a 5 to 10-centimeter-thick layer of water advances up to 12 kilometers inland. As this flow coincides with tides and occurs at relatively warm temperatures, researchers concluded that this water layer is seawater, not glacial meltwater. Currently, the grounding line is retreating at a rate of approximately 500 meters per year, but the intrusion of seawater mentioned above could accelerate this retreat, causing the ice sheet to move more rapidly towards the ocean.
Rignot highlighted that current computer models predicting the future changes of the Thwaites Glacier do not account for seawater intrusion beyond the grounding line. A study from a decade ago found that such intrusion could double the glacier's melting rate. Consequently, the future of the "Doomsday Glacier" appears even more "ominous" than previously imagined.
For more information, refer to the related paper: https://doi.org/10.1073/pnas.2404766121
