Major glacier in northern Greenland shows dramatic signs of weakening

An international collaboration of researchers from Europe and the United States have detected a dramatic retreat of a major glacier in North Greenland, long considered stable.

The Petermann Glacier in North Greenland is one of the largest glaciers on the Greenland ice sheet. This glacier is one of the only ones in the Arctic to have a floating extension called an ice shelf, which is more than 60 km long. These platforms are essential elements because they buttress all the ice that does not float. Measuring the changes affecting these platforms is therefore crucial, because their disappearance can lead to an increase in the discharge of icebergs into the ocean and thus an increase in sea level.

The Petermann Glacier was considered stable because it had reacted very little to the warming of the ocean and atmosphere, which has largely affected other Greenlandic glaciers.

Using several hundreds of satellite imagery data from the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA) and the Italian Space Agency (ASI), an international collaboration of scientists was able to observe the changes affecting the Petermann ice shelf during the last 30 years: “Using cutting-edge interferometric methods, we were able to measure very precisely the position of the glacier’s grounding line.”, said Romain Millan, postdoctoral researcher at the Institut des géosciences de l’environnement (IGE/OSUG, CNRS / IRD / UGA / Grenoble INP) and lead author on the paper. The grounding line is the limit where the glacier starts to float to become an ice shelf. “Measuring the position of the grounding line is key because it has a great control on the glacier stability” said Pietro Milillo, a researcher at University of Houston and co-author on the study.

While the glacier has remained relatively stable since the 1990s, researchers have recently observed a dramatic change in the glacier behavior. “During the last seven years, we witnessed a series of events which show all the signs of a glacier destabilization.” said R. Millan.

Between 2014 and 2015, the glacier flow started to accelerate significantly. After this event, two large cracks opened, which split up the ice shelf in three different parts. Since 2017, the glacier is active again and its grounding line has receded dramatically, “Between 2017 and 2021, the glacier grounding line retreated by 5 km!” said R. Millan,”It is far exceeding the natural variability that we usually observe with Petermann.”

For the scientists, these events suggest an imminent destabilization of Petermann, which has long been spared until now : “This is really important news for this glacier and Greenland in general”, said Jeremie Mouginot, researcher at IGE and second author of the study. Since the 1970’s, the scientists have measured a significant increase in ocean temperatures in this area. Changes in ocean temperatures have the capacity to increase the melting of ice shelves from below, which is a crucial process controlling their stability. “We believe that the dramatic events occurring at the moment are the consequences of a long-term weakening of the ice shelf, which is in part due to warmer ocean waters”, said R. Millan.

The weakening of platforms is an important issue, especially in Antarctica, where most glaciers are ending in floating extensions, like the Petermann Glacier. “Since Greenland is subject to a wider range of climate forcings, observing what is happening there could help us to better understand what could happen to Antarctica in the future” said R. Millan. After the deadly breakup of the Marmolada glacier in the Alps and in Tajikistan, rapid glacier collapses are accumulating in all latitudes, as ever more glaring signs of the changes affecting our planet, hence calling for immediate action to tackle the climate crisis.

This project was funded by the Agence National de la Recherche, data were processed at the Institut des Geosciences de l’Environnement and at University of Houston, USA.

Reference
Millan, R., Mouginot, J., Derkacheva, A., Rignot, E., Milillo, P., Ciraci, E., Dini, L., and Bjørk, A.: Ongoing grounding line retreat and fracturing initiated at the Petermann Glacier ice shelf, Greenland, after 2016, The Cryosphere, 16, 3021–3031, https://doi.org/10.5194/tc-16-3021-2022, 2022.

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Updated on 25 August 2022