Warming-Driven Glacier Melt Leads to ‘River Piracy’

As glaciers around the world are retreating rapidly, communities will be robbed of their rivers in the years to come, warn scientists.

They draw our attention to geomorphological phenomenon called ‘river piracy’, or ‘stream capture’, occurring when a stream or river drainage system is diverted from its own bed, and flows instead down the bed of a neighbouring stream. This can happen when there is a glacier melt, erosion, tectonic earth movement or landslide.

Alaskan river under threat

A new study has found that a major Alaskan river is under threat of being redirected in this way – stealing an essential source of water away from the ecosystem and people that rely on it. Scientists attribute this river piracy to glacier melt caused by global warming.

Scientists from the US National Park Service have predicted that a rapidly retreating glacier within Glacier Bay national park and reserve in Alaska is expected to change the course of the Alsek River it feels. The waterway originates in the St Elias mountain range in Canada and flows south into Alaska, entering the Pacific Ocean in a channel that flows through Dry Bay. Based on the researchers’ predictions, the mouth of the Alsek River could end up almost 30 km to the south east within the next 30 years. That has an impact on the surrounding wildlife, including the fish in the Alsek River and the community that has built up around the Dry Bay. The Dry Bay is a major point for fishery and rafting activities.

Impact on Slims River

Scientist had earlier documented a river piracy event in 2016 in Canada’s Yukon Territory. A period of intense melting of the Kaskawulsh glacier permanently redirected the meltwater of the Slims River. The melting formed an ice-walled canyon, which redirected the Slims River flowing out to the Bering Sea, to flow into the Kaskawulsh River instead. River piracy which typically takes centuries happened over the course of one spring here.

It redrew the landscape of the area and affected the people, animals and birds are dependent on the river. Shifts in sediment transport, lack chemistry, fish populations, wildlife behaviour, and other factors continued to occur as the ecosystem adjusted to the new reality.

While river piracy, or a stream capture, is known to have happened in the past because of swings in Earth‘s climate, most of those examples were from thousands of years ago. These instances are the firsts attributed to human-caused climate change.

 

Picture Credit : Google

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