Glaciers are Melting Faster With Far Greater Consequences Than Expected

Pope Glacier in Antarctica taken by Operation Ice Bridge in 2016. (Credit: NASA)

https://www.dlr.de/content/de/artikel/news/2022/01/20220128_gletscher-schmelzen-schneller-als-erwartet.html

  • West Antarctica: Smith, Pope and Kohler glaciers are melting faster than expected.
  • Critical area: Free-floating undersides of glaciers melt the most.
  • Ice masses in West Antarctica could raise sea levels by up to 1.3 meters.
  • Focus: space travel, earth observation, global change, TanDEM-X

COLOGNE, Germany (DLR PR) — The South Pole has new problem children. A group of smaller glaciers are melting faster than expected: Pope, Smith and Kohler. So far, the neighboring ice giants Thwaites and Pine Island have been the focus of research because they are very fragile and could cause global sea levels to rise by up to 1.2 meters. The German Aerospace Center (DLR) has uncovered and analyzed the changes in West Antarctica together with international research partners. Using special radar data from the TanDEM-X and COSMO-SkyMed satellite missions, they tracked down the causes of the rapid melting of the smaller glaciers.

The knowledge gained is important in order to better understand glacial processes and thus predict the development of the entire Antarctic. In the future, climate researchers will then be able to calculate even more precisely how much the sea level will rise and which protective measures will be most effective. The new study is currently in the journal “NatureGeoscience” published. It is the result of a collaboration between the University of Houston, the DLR Institute for High Frequency Technology and Radar Systems, the University of California, the University of Grenoble Alpes and the Italian Space Agency (ASI).

West Antarctica: TanDEM-X terrain representation of the Kohler, Smith and Pope glaciers. (Credit: DLR (CC BY-NC-ND 3.0)

Complex melting processes

The Pope, Smith, and Kohler glaciers have shrunk significantly over the past 30 years: they have thinned, lost ice shelves to the ocean, and retreated further inland. What was striking here was the decline in the touchdown line, i.e. the limit at which the ice loses contact with the mainland and begins to float on the sea. The radar experts therefore focused their attention on this transition area. For the first time, they were also able to demonstrate drastic changes in the Pope Glacier, which retreated in 2017 within just three months at a rate of 11.7 kilometers per year.

Earth observation satellites have become indispensable for glacier and climate research. 

“We used to have to wait years before we finally had usable data on the polar regions. Thanks to the high-performance satellite missions TanDEM-X and COSMO-SkyMed, we can now analyze the polar regions on a monthly basis. From the recordings and with new methods for data evaluation, we also get a completely new level of detail to further improve glacier and climate models,” says DLR guest scientist Prof. Pietro Milillo from the University of Houston, Texas. Through the targeted analysis of TanDEM-X time series, they were even able to track the changes every two weeks instead of every four weeks.

The new study thus provides another important piece of the puzzle for glacier and climate research. The physical melting processes of Pope, Smith and Kohler are identical for the other glaciers around the Amundsen Sea. The giants Thwaites and Pine Island could destabilize the rest of West Antarctica with their high mass losses, with devastating consequences for life on Earth. If future climate models take into account how much a floating ice sheet melts from below, they could also determine the retreat of glaciers even more precisely.

Altitude changes and touchdown line movement (Credit: TanDEM-X data, grounding lines derived from COSMO-SkyMed)

Key process: Melting of the free-floating underside of the glacier

The underside of a glacier is hidden from view, so ice loss cannot be measured directly. With the help of digital TanDEM-X elevation models, the scientists were now able to precisely determine this hidden melting rate. For example, while overland Smith Glacier melted at about five meters per year from 2011 to 2019, the free-floating glacier bottom melted at a rate of about 22 meters per year. In fact, in certain places, Smith has had melt rates in excess of 100 meters per year, peaking at 140 meters per year in 2016.

Some investigations with climate models confirmed that the computer calculations of the grounding line agree with the actual measurements only when they take into account the new values ​​of the melting rate. In addition, the new radar data and findings have the research network International Thwaites Glacier Collaboration provided significant support in preparing measurement campaigns and selecting suitable sites for test drilling.

“In order to determine the melt rates, we at DLR also generated more than 240 digital TanDEM-X elevation models, which depict West Antarctica from 2011 to 2019 with great precision,” says co-author Dr. Paola Rizzoli from the DLR Institute of High Frequency Technology and Radar Systems. 

This includes well-established production: The German Space Operations Center is responsible for operating TerraSAR-X and TanDEM-X and commands the twin satellites for the required images. The radar data is recorded by the German Remote Sensing Data Center at its receiving stations in Neustrelitz, Inuvik (Canadian Arctic) and GARS O’Higgins (Antarctica). The DLR Institute for Remote Sensing Technology supplies the input data for the automated TanDEM-X processing chain. The interferometric processing,

Future L Band

Germany’s leading position in the field of radar research and radar technology enables the development of a new generation of radar satellites that expand the urgently needed data base for research and the global community. In this way, gaps in knowledge can be closed and solutions for global societal challenges can be developed. The technical and scientific skills can be further expanded for future satellite missions, especially in the L-band.

Radar satellites with a long-wave frequency range have the advantage that they can also see through vegetation down to the ground. In the polar regions, an L-band radar mission could map glacier structures and dynamic processes such as melting even more precisely. Germany could continue to set new standards in earth observation, observe global change with a new quality and make important recommendations for possible action.