Climate Change May be Causing the Greenland Ice Sheet to Contribute More Meltwater to the Ocean

Climate change may be altering the Greenland ice sheet in such a way that it's causing it to looks its ability to buffer its contribution to rising sea levels. The findings could mean some massive contributions to sea level rise in the future.

In this latest study, the researchers analyzed data from three expeditions to the Greenland ice sheet in 2012, 2013 and 2015. In 2013 in particular, the researchers drilled firn cores into the interior of the Greenland Ice Sheet. Firn is a multi-year compacted snow that is not as dense as glacier ice. Instead, it forms a porous near-surface layer over the ice sheet.

"We were interested in the thin porous near-surface firn layer, and how its physical structure is changing rapidly with climate change," said William Colgan, co-author of the new study, in a news release. "The study looked at very recent climate change on the ice sheet, how the last couple of years of melt have really altered the structure of the ice sheet firn and made it behave differently to future melt."

The researchers found that an extreme melt occurred in 2012, which caused a layer of solid ice, several meters thick, to form on top of the porous firn in the low elevation areas of the ice sheet. In subsequent years, meltwater couldn't penetrate vertically through the solid ice layer. Instead, it drained along the ice sheet surface toward the ocean.

"It overturned the idea that firn can behave as a nearly bottomless sponge to absorb meltwater," said Colgan. "Instead, we found that the meltwater storage capacity of the firn could be capped off relatively quickly."

In other words, the findings show that the firn reacts quickly to a changing climate. This, in particular, is important to note when estimating global sea level rise in the future.

The findings are published in the journal Nature Climate Change.

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