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Ice sheets mobilize trace elements

Meltwater from the frozen giants is enriched in iron and other metals

by Ariana Remmel
November 28, 2020 | A version of this story appeared in Volume 98, Issue 46


Pictured is a milky-colored glacial meltwater river that has drained from the Greenland Ice Sheet.
Credit: Kathy Kasic
Meltwater from the Greenland Ice Sheet looks milky because of the suspended sediment, called rock flour, which carries trace elements such as iron.

Earth’s two remaining ice sheets, also called continental glaciers, are more active geochemists than we previously knew, according to a new study. Researchers led by Jon Hawkings, a biogeochemist at Florida State University and the German Research Center for Geosciences, measured the abundance of 17 trace elements in samples of meltwater from the Greenland Ice Sheet and a lake beneath the Antarctic Ice Sheet. They found that these water samples are more enriched in important micronutrients such as iron compared with rivers and the surrounding ocean (Proc. Natl. Acad. Sci. U.S.A. 2020, DOI: 10.1073/pnas.2014378117). The trace elements can be found fully dissolved or suspended as nanoparticles, and they likely come from the bedrock beneath the frozen giants. That’s because ice sheets are “natural bulldozers” that pulverize landscapes as they move, and water trapped in subglacial lakes can liberate minerals from the surrounding rock, Hawkings says. “We didn’t have a good idea of how important ice sheets might be for cycling of elements,” he says. Now Hawkings thinks these results are just the tip of the iceberg, metaphorically speaking, as scientists start to reevaluate the role these frozen masses play in contributing trace elements to waterways, especially as the ice sheets melt because of climate change.


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