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The natural world. Looking pretty for 3.5b years.

There Once Was A River

There Once Was A River

Author: Hugh Bollinger/Sunday, January 13, 2019/Categories: natural history, sustainability, environment, adventure , climate change

                       Slims River Flow, 2015-2016 (credit: Sentinel-2 Earth Observing satellite, ESA)

Catastrophic environmental events happen infrequently but when they do, they can leave profound geographic, ecological, and even economic impacts. In the equalivant of a geological 'blink of an eye', a Canadian river vanished in little more than 3 days. The Kaskawulsh Glacier abruptly altered its drainage patterns when an ice canyon collapsed at the head of the massive frozen river. Satellite images and river sensors showed that glacial meltwater had been rerouted the river from discharging northwards to the Bering Sea, instead it was now flowing south into the Pacific Ocean. Researchers with the Universities of Washington and Illinois called the dramatic alterations a case of 'river piracy'.

The Kaskawulsh Glacier originally formed a barrier over a rock divide that segregated meltwater into two glacial outflows: one into the Slims River that eventually reached the Bering Sea while the second flowed into the Kaskawulsh River, which emptied into the Pacific Ocean. As the glacier retreated, its terminus had contracted so far that the glacial outflow waters were allowed to change course to join the Kaskawulsh River. River gauges showed an abrupt drop over just four days. In the process the Slims River went dry. Jim Best, one of the lead researchers, said an event like this typically happens over long time periods, often tens of thousands of years, but nothing like this had ever been observed before.


     Kaskawulsh Glacier Ice Canyon Carrying Meltwater Towards the Gulf of Alaska. (credit: Jim Best, U. of Illinois)

According to an announcement on their study: Dan Shugar of the Sediments Hazards Earth-surface Lab at the University of Washington said: "People had looked at the geological record — thousands or millions of years ago — not the 21st century, where it’s happening under our noses"

The field data was published in Nature Geoscience and suggests that the abrupt changes observed can be attributed to human-induced climate change. The researchers determined that the chance of the glacial collapse, and the resulting river reversal, having occurred from natural variability was 0.5%. Jim Best, another author of the study said: “So it’s 99.5% that this event occurred due to warming over the industrial era" until a glacial tipping point was crossed.

We expect more examples of dramatic events like what happened to the Slims River as climate change accelerates.



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