Glacial meltwater lakes have grown by half since the 1990s

Enlarge / Glacial meltwater lakes in the Bhutan Himalaya. (credit: NASA EO)

When we talk about sea level rise, one of the causes we have to mention is the shrinking of mountain glaciers, which are often overlooked as we focus on the monster ice sheets of Greenland and Antarctica. Seas rise because glacial ice melts and meltwater makes its way to the ocean, turning land ice into ocean volume. But this description is obviously a simplification. For mountain glaciers, the meltwater has to do some traveling to reach the ocean, and interesting things may happen along that journey.

That journey creates a known blind spot in the math. Sea level rise is measured, and the change in glacial ice is tracked as best we can, but there's no global estimate for anything in between. A new study led by the University of Calgary's Dan Shugar fills in that gap by assessing meltwater lakes near glaciers-and confirms it doesn't affect the sea level math much.

As was the case with a recent study of ice fractures in Antarctica, the primary challenge here is labor. Finding and mapping every glacial lake in satellite images would be a herculean lift-it has to be automated to be practical. So the researchers grabbed some 255,000 satellite images of glacial areas between 1990 and 2018 and turned to computerized detection to outline each lake. They then relied on an average estimate for the relationship between a lake's surface area and volume in bodies like these to calculate changes over time based on the lake outlines.

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