A team of glaciologists at the University of California in Irvine (United States) has revealed the most accurate portrait of the contours of the earth below the Antarctic ice sheet, and in doing so, they have helped identify what regions of the continent will be more or less vulnerable to future climate warming.
The results of this topographic study of Antarctica – called 'BedMachine'– have been published this week in the magazine Nature Geoscience.
Among the most surprising data of the 'BedMachine' project are the discovery of stabilizing ridges that protect ice that flows through the Transantarctic mountains; a bed geometry that increases the risk of rapid ice melting in the Thwaites and Pine Island glaciers sector of West Antarctica; a bed under the glaciers of Support Force Glacier which is hundreds of meters deeper than previously thought, making those ice sheets more susceptible to withdrawal, and the deepest land canyon in the world beneath the Denman glacier, in East Antarctica.
"There was A lot of surprises across the continent, especially in regions that had not been mapped previously in great detail with radar, "the study's lead author, Mathieu Morlighem, associate professor of earth system science at the UCI, has advanced in a statement.
"Ultimately, the Antarctic BedMachine presents a mixed image: ice currents in some areas are relatively well protected by their underlying soil characteristics, while others in retrograde beds show a increased risk of instability potential of the sea ice sheet, "he added.
The new Antarctic bed topography product was built using ice thickness data from 19 research institutes different dating back to 1967, covering almost a million miles of radar probes.
In addition, the creators of 'BedMachine' used bathymetry measurements from the ice shelf of NASA's Operation IceBridge campaigns, as well as the speed of ice flow and seismic information, where it was available. Some of these same data have been used in other topography mapping projects, producing similar results when viewed broadly.
"By using 'BedMachine' to approach particular sectors of Antarctica, they have found essential details as protrusions and hollows under the ice that can accelerate, decrease or even stop the removal of glaciers, "added Morlighem.
Previous mapping methods in Antarctica that were based on radar surveys have been generally effective, but with some limitations. While the airplanes fly in a straight line over a region, the radar systems mounted on the wings emit a signal that penetrates the glaciers and the ice sheets and bounces from the point where the ice meets the mainland.
Subsequently, glaciologists use interpolation techniques to fill in the areas between the runways, but this has proven to be an incomplete approach, especially with rapidly flowing glaciers.
For its part, 'BedMachine' is based on the fundamental method of mass conservation based on physics to discern what is between the radar survey lines, using highly detailed information about the movement of the ice flow that dictates how ice moves around the varied contours of the bed. This technique was fundamental in the conclusion of the research team regarding the true depth of the Denman channel.
"Older maps suggested a shallow canyon, but that was not possible; something was missing. With mass conservation, by combining the existing radar study and the ice movement data, we know how much ice the cannon fills, which, according to our calculations, is at 3,500 meters below sea level, the deepest point on earth. Since it is relatively narrow, it has to be deep to allow so much ice mass to reach the coast, "said Morlighem.
By basing its results on the ice surface speed in addition to the ice thickness data of the radar surveys, 'BedMachine' has been able to present a more accurate and high resolution representation of the topography of the bed.
Already applied in the Arctic
This methodology has been used successfully in Greenland in recent years, transforming the understanding of cryosphere researchers on the ice dynamics, the oceanic circulation and the mechanisms of withdrawal of the glaciers.
Applying the same technique to Antarctica is especially difficult Due to the size and remoteness of the continent, but, Morlighem has pointed out, 'BedMachine' will help reduce uncertainty in projections of sea level rise of numerical models.
Morlighem has added that the mapping of the topography of the future bedon land It could be greatly improved by mapping the depth of the seabed at sea and under floating ice, which is an active study area at this time.
In this new work, Morlighem has also suggested that the study of fast-flowing Antarctic ice sheets would benefit from polls along the runways perpendicular to the direction of the flow, "especially upstream of the Academy and Support Force glaciers, along the Gould coast near the Ross ice barrier, and along the coast of Wilhelm II, between the Denman and Lambert glaciers, "he concluded.