SAN FRANCISCO — A lot of the information concerning the Thwaites Glacier, a Florida-sized slab of ice that’s melting and presently contributing about 4 p.c of world sea stage rise, is unhealthy. However a bit of fine information could have emerged.
A seismic survey of the mattress beneath an upstream part of Thwaites has revealed tough high-rises of earth underneath the Antarctic glacier, that are comparable in top to the Manhattan skyline, glaciologist Coen Hofstede reported December 12 at a information convention throughout the American Geophysical Union fall assembly. These rugged rises could also be snagging the glacier’s underbelly, slowing its circulate towards the ocean and mitigating world sea stage rise.
Glaciers circulate considerably like rivers, however a lot slower. The place Thwaites shops into the ocean, it connects to a floating shelf of ice that braces and partially restrains the glacier. That ice shelf was as soon as pinned upon an underwater mountain, which helped stabilize it (SN: 12/13/21). However now the shelf is so deteriorated that it’s principally unhitched, Erin Pettit, a glaciologist at Oregon State College in Corvallis, stated on the information occasion.
Happily, although, the glacier “is just not going to immediately circulate off land,” thanks partly to what’s been found upstream, stated Pettit, who was not concerned within the discovery.
Greater than 70 kilometers inland from Thwaites’ ice shelf, Hofstede and his colleagues carried out a seismic survey to probe the glacier’s underbelly. The staff connected a 1.5-kilometer-long daisy-chain of seismometers to a automobile geared up with a vibrating plate. Then they drove a roughly 200-kilometer-long stretch of the glacier, utilizing the plate to generate seismic waves and the seismometers to report the waves’ reflectance off layers of ice and earth beneath. “It’s virtually like radar,” stated Hofstede, of the Alfred Wegener Institute Helmholtz Heart for Polar and Marine Analysis in Bremerhaven, Germany.
The seismic waves revealed rises underneath Thwaites which can be 10 to twenty kilometers lengthy and toothed with blocks of sediment. These blocks stood as much as 100 meters tall above the rises and stretched for as much as a number of kilometers horizontally.
The info confirmed that the upstream faces of those blocks seem like underneath higher stress than their downstream sides, and that there could be layers of deformed ice throughout the glacier above the rises. Hofstede hypothesizes that the rises and blocks are slowing Thwaites’ circulate as its ice presses towards them.
Utilizing computer systems to simulate the circulate of Thwaites glacier exhibits that “it will get hung up on tall options,” stated glaciologist Ben Smith of the College of Washington in Seattle, who was not concerned within the work.
The rises are in all probability associated to a rift system, an space the place tectonic forces have pulled the bottom aside, Hofstede stated. Underneath Thwaites, these rifts run roughly perpendicular to the glacier’s ice circulate, form of like velocity bumps on a avenue.
The findings will permit for extra nuanced simulations of the glacier’s evolution, Hofstede stated, that are essential for understanding charges of sea stage rise.