Satellites capture massive drainage of proglacial lake in remote Patagonia

Only satellites watched as the world’s fourth-largest proglacial lake suddenly dried up in 2020. Hokkaido University researchers have now uncovered the event and analyzed its cause: the collapse of a sediment hump at the lake’s outlet.

Proglacial lakes form when meltwater from retreating glaciers is held back by ice or by a moraine left by the same or another glacier. A warming climate is contributing to the recent global increase in the number and volume of these lakes, and they themselves are contributing to glaciers melting even faster. However, these lakes can empty very quickly when the dams containing them fail for one of several reasons.

Such a catastrophic event not only poses a direct safety risk to humans, but also affects downstream ecosystems due to the sudden influx of a large amount of fresh water. It is therefore important to monitor proglacial lakes and study their interactions with their environment. Unfortunately, this is difficult due to their often remote location.

Glacier scientist Shin Sugiyama of Hokkaido University and PhD student Shuntaro Hata were studying glacial fluctuations in Chilean Patagonia using satellite imagery, when they noticed that proglacial Lake Lago Greve had shrunk significantly in the short span of time between April and July 2020. findings in the journal Communication Earth & Environmentthey add further analysis of the available data confirming that the lake’s water level has dropped by 18 meters, translating to a loss of 3.7 cubic kilometers (or gigatons) of water – the largest such event to date by a satellite has been observed.

This massive water loss even measurably changed the Earth’s gravitational field, as recorded by GRACE satellites, although quantitative data from these satellites is not consistent with the actual amount of water being drained. Finally, from careful analysis of the satellite images and topographical data from before and after the event, they were able to conclude that the cause of the release was likely the collapse of a sediment hump close to the lake’s outlet.

This research reveals many interesting aspects. First, it points the way for future research into glacial dynamics. Sugiyama explains, “These results provide detailed information about large-scale glacial lake eruptions, which occur very rarely, and are important for understanding disasters caused by glacial lake failure.”

It also highlights the possibility and current limitations of using GRACE satellite data to observe such events. The researchers write, “The importance of GRACE measurements in studying such events would increase if the calculation of the gravitational field measurements is adjusted for localized events.”

And finally, the study provides concrete data that can be used to better understand the dynamics of the interactions between glaciers and the lakes that form them, as “the observed changes in the water level of glacial lakes can be used to predict changes in glacier influx.” forecast in the lakes.”