Arctic river ice deposits rapidly disappearing

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Arctic river ice deposits rapidly disappearing

Climate change is causing thick ice deposits that form along Arctic rivers to melt nearly a month earlier than they did 15 years ago, a new study finds.

River icings form when Arctic groundwater reaches the surface and solidifies on top of frozen rivers.

They grow throughout the winter until river valleys are choked with ice. Some river icings have grown to more than 10 square kilometers (4 square miles) in area – roughly three times the size of New York’s Central Park – and can be more than 10 meters (33 feet) thick.

In the past, river icings have melted out around mid-July, on average.

But a new study measuring the extent of river icings in the U.S. and Canadian Arctic shows most river icings disappeared 26 days earlier, on average, in 2015 than they did in 2000, melting around mid-June.

In addition, the study found most icings that don’t completely melt every summer were significantly smaller in 2015 than they were in 2000. Watch a video of river icings here.

“This is the first clear evidence that this important component of Arctic river systems – which we didn’t know was changing – is changing and it’s changing rapidly,” said Tamlin Pavelsky, a hydrologist at the University of North Carolina Chapel Hill and lead author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union.

Scientists have studied the effects of climate change on other types of Arctic ice like glaciers and sea ice, but until now no study has systematically looked at whether river icings are changing in response to a warming climate, according to the authors.

Although the decline in river icings is likely a result of climate change, the authors are unsure whether the decline in river icings is a direct result of rising temperatures or if climate change is altering how rivers and groundwater interact.

“While glaciers tell us about climate in the mountains and sea ice tells us about sea-atmosphere interactions, the processes that control river icing may offer great insight into how groundwater and surface waters are connected in the Arctic and how our headwaters will be connected to the ocean in the future,” said Jay Zarnetske, a hydrologist at Michigan State University in East Lansing, Michigan, and co-author of the study.

The decline in river icings is remarkably rapid and if it continues, it could have huge impacts on Arctic river ecosystems, Pavelsky said.

River icings are found all over the Arctic and create wide channels that are important habitats for animals and fish. So much water is tied up in river icings that when they melt in summer, usually in July and August, they keep rivers flowing that might otherwise dry up, providing important freshwater habitat for fish and other animals, he said.

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News source: American Geophysical Union. The content is edited for length and style purposes.
Figure legend: This Knowridge.com image is credited to Jay Zarnetske.