Research by a new doctorate. finds the deformation of the crust of the planet, with far-reaching effects.
Melting polar ice is not only changing the level of our oceans, it is also changing planet Earth itself. Newly established Ph.D. Sophie Coulson and her colleagues explained in a recent article in Geophysical research letters that as the glacial ice of Greenland, Antarctica and the Arctic islands melts, the earth’s crust beneath these land masses is deforming, an impact that can be measured hundreds or even thousands of kilometers away.
“Scientists have done a lot of work directly under ice caps and glaciers,” said Coulson, who did his work in the Department of Earth and Planetary Sciences and received his doctorate in May from the Graduate School of Arts. and Sciences. “So they knew that would define the region where the glaciers are, but they didn’t realize it was on a global scale.”
By analyzing satellite data on melting from 2003 to 2018 and studying changes in the earth’s crust, Coulson and his colleagues were able to measure the horizontal displacement of the crust. Their research, which was highlighted in Nature, found that in some places the crust moved more horizontally than it lifted. In addition to the surprising breadth of its reach, the Nature paper pointed out, this research offers a potentially new way to monitor modern ice mass changes.
To understand how melting ice affects what lies below, Coulson suggested imagining the system on a small scale: “Think of a plank of wood floating above a tub filled with water. As you push the board down, the water below moves down. If you pick it up, you will see the water moving vertically to fill that space.
These movements have an impact on the continuation of the melting. “In parts of Antarctica, for example, the rebound of the crust changes the slope of the bedrock below the ice sheet, and this can affect the dynamics of the ice,” said Coulson, who worked in the laboratory of Jerry Mitrovica, Frank B. Baird, Jr. Professor of Science.
The current melting is just the most recent movement observed by researchers. “The Arctic is an interesting region because, in addition to modern ice caps, we also have a lasting signal from the last ice age,” Coulson explained. An ice cap once covered what is now northern Europe and Scandinavia during the Pleistocene, the ice age that began about 2.6 million years ago and lasted until there about 11,000 years old. “The Earth is actually still bouncing after the ice melts.”
“On recent timescales, we think of the Earth as an elastic structure, like a rubber band, whereas in timescales of thousands of years, the Earth acts more like a very slow fluid,” Coulson said. , explaining how these new repercussions are occurring. to be superimposed on older reverbs. “The processes of the Ice Age take a very, very long time to unfold, so we can still see the results today.”
The implications of this movement are considerable. “Understanding all of the factors that cause the crust to move is really important for a wide range of earth science issues. For example, to accurately observe tectonic movements and seismic activity, we need to be able to separate this movement generated by modern ice mass loss, ”she said.
Coulson is continuing his research as a postdoctoral director at the Los Alamos National Laboratory in New Mexico as part of a climate group working on future projections of ice caps and ocean dynamics.
Glenn Antony Milne, professor of earth and environmental sciences at the University of Ottawa, explained that understanding the extent of this movement clarifies all studies of the earth’s crust. “Sophie’s work is important because it is the first to show that recent mass loss from ice caps and glaciers causes 3D movement of the Earth. [solid] surface of greater magnitude and spatial extent than previously identified, ”he said. “In addition, one could search for this signal in larger scale regional navigation satellite systems data sets to, in principle, produce improved constraints on the distribution of ice mass fluctuations and / or ice flow. solid structure of the Earth. “
“The Global Fingerprint of Modern Ice-Mass Loss on 3-D Crustal Motion” by Sophie Coulson, Mila Lubeck, Jerry X. Mitrovica, Evelyn Powell, James L. Davis and Mark J. Hoggard, August 16, 2021, Geophysical research letters.
DOI: 10.1029 / 2021GL095477
“There is so much melting ice that the earth’s crust is moving”, Research update, August 24, 2021, Nature.
DOI: 10.1038 / d41586-021-02285-0