Genuine, Modern River Piracy

[kaima]

It may be an old story that predates human history, but it appears to have been detected in near-real time!

earthobservatory.nasa.gov/images/90116/river-piracy-in-the-yukon

River Piracy in the Yukon

You can't see much change in the Kaskawulish River, but you can catch the difference easily looking at the Slims River:

in two still photos (the original link has a slider to alternate between the two)




In the spring and summer of 2016, Daniel Shugar and colleagues witnessed an act of piracy in Canada’s Yukon Territory. The Kaskawulsh River hijacked the Slims River, stealing much of its supply of water and dramatically reshaping the region’s drainage.

The ongoing retreat of the Kaskawulsh glacier in the St. Elias Mountains spurred this rarely seen process of “river piracy.” For years, meltwater from the Kaskawulsh glacier has fed two large lakes at the glacier front; those lakes feed the Slims and Kaskawulsh rivers. Previously, most of the water flowed northward via the Slims River and into a watershed that ultimately empties into the Bering Sea. A lesser amount flowed southward via the Kaskawulsh into a watershed that empties into the North Pacific Ocean.

Roles reversed in spring 2016—that’s when pilots first informed Shugar, a geomorphologist at University of Washington-Tacoma, that the Slims River was running low and the Kaskawulsh River was flooded. Shugar and colleagues visited the site in August, and that’s when the magnitude of the change “really sunk in.”

The river piracy is visible in this image pair, acquired with the Operational Land Imager (OLI) on Landsat 8. The false-color images combine observations of shortwave infrared, near-infrared, and red light (OLI bands 6, 5, 4) to better distinguish areas of water (dark blue) from the surrounding landscape. Vegetation is green, and snow and ice are light blue.

The first image was acquired on June 23, 2015, when the Slims River filled its valley. The second image was acquired on June 18, 2016, by which time the Slims River was just a narrow ribbon of water. Meltwater from the thinning, retreating glacier carved a new channel at the front of the glacier (just a few pixels wide in this image) that now connects a series of azure lakes and routes most of the meltwater into the large lake feeding the Kaskawulsh River. As a result, the Kaskawulsh appears much wider. Turn on the image comparison tool to see the change.

More changes followed. According to Shugar, water draining northward via the Slims River continued to dwindle throughout the season and by late summer, the Slims was disconnected from its source. The diversion, the researchers say, is likely permanent, and could affect the local ecosystem.

“Our climate is changing, but it’s not only temperatures and sea levels that are impacted; other things are occurring,” Shugar said. “This river piracy is one such impact, and we expect to be thrown a few curve balls when it comes to these changes going forward. We need to continue studying and monitoring our Earth systems, both on the ground and from space, so as to better understand the coming changes, and prepare for them.”

NASA Earth Observatory images by Jesse Allen, using Landsat data from the U.S. Geological Survey. Story by Kathryn Hansen.
earthobservatory.nasa.gov/images/90116/river-piracy-in-the-yukon

[kaima]

www.washington.edu/news/2017/04/17/retreating-yukon-glacier-caused-a-river-to-disappear/

This gives a preview of what will happen on a huge (a good Trumpism) scale when the glaciers in the Himalayas melt and the rivers in India dry out .. yet the consequensces will be even huger/<humongous> (a better Trumpism)

April 17, 2017

Retreating Yukon glacier caused a river to disappear
Hannah Hickey
UW News



The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century.


chunks of sediment-covered ice
A close-up view of the ice-walled canyon at the terminus of the Kaskawulsh Glacier, with recently collapsed ice blocks. This canyon now carries almost all meltwater from the toe of the glacier down the Kaskawulsh Valley and toward the Gulf of Alaska.Jim Best/University of Illinois

Last spring, its retreat triggered a geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska.

This capture of one river’s flow by another, documented in a study led by the University of Washington Tacoma and published April 17 in Nature Geoscience, is the first known case of “river piracy” in modern times.

“Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes,” said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. “People had looked at the geological record — thousands or millions of years ago — not the 21st century, where it’s happening under our noses.”


two satellite images
Images captured by the European Space Agency’s Sentinel2 satellite in 2015 and 2016 show a dramatic drop in the Slims River’s flow. The receding toe of Kaskawulsh Glacier is seen at the bottom. Kluane Lake can be seen at the top of the 2016 image. Water now flows east and then south via the Kaskawulsh River.European Space Agency

River piracy, also known as stream capture, can happen due to tectonic motion of Earth’s crust, landslides, erosion or, in this case, a change in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate.

Shugar and co-authors Jim Best at the University of Illinois and John Clague at Canada’s Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016.

By late summer, “there was barely any flow whatsoever. It was essentially a long, skinny lake,” Shugar said. “The water was somewhat treacherous to approach, because you’re walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping.”

The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river’s disappearance.


A Sept. 2, 2016 aerial photo shows the meltwater stream along the toe of Kaskawulsh Glacier, seen on the left, that is diverting fresh water from one river to the other.
A Sept. 2, 2016 aerial photo shows the meltwater stream along the toe of Kaskawulsh Glacier, seen on the left, that is diverting fresh water from one river to the other.Dan Shugar/University of Washington Tacoma

“For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet,” Shugar said. “A 30-meter (100-foot) canyon had been carved through the terminus of the glacier. Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid.”

That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar said, since the glacier’s toe was sitting on a geologic divide.

Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon’s largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated.

“The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change,” Clague said.



lake with sandy beach
Less input from the Slims River has lowered the water level of Kluane Lake, the largest lake in the Yukon, exposing sediments and creating dust storms.Jim Best/University of Illinois

The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow.

On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River’s water.


river headwaters
The Kaskawulsh River, seen here near its headwaters, is running higher now thanks to the addition of water that used to flow into the Slims River.Jim Best/University of Illinois

Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar said.

“So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise,” Shugar said. “Our study shows there may be other underappreciated, unanticipated effects of glacial retreat.”

The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by UW co-author Gerard Roe shows a 99.5 percent probability that this glacier’s retreat is showing the effects of modern climate change.

“I always point out to climate-change skeptics that Earth’s glaciers are becoming markedly smaller, and that can only happen in a warming climate,” Clague said.

Other co-authors are Christian Schoof at the University of British Columbia, Michael Willis at the University of Colorado and Luke Copland at the University of Ottawa. The study was funded by the University of Washington Royalty Research Fund, Parks Canada, Yukon Geological Survey, the Natural Sciences and Engineering Research Council of Canada, the University of Ottawa and the University of Illinois.

[Jaga]

Kai,

beautiful scenery!
at least this happened in the area that is not that does not affect humans. I remember during our Alaska cruise many seeings of the glaciers that were disappearing.

Just a couple of days ago I saw this info:
www.livescience.com/antarctica-bleeds-watermelon-snow.html

Spooky 'blood snow' invades Antarctic island
By Brandon Specktor - Senior Writer 5 days ago

The blood-red algae behind the phenomenon could kick off a runaway feedback loop of warming, researchers warned.

[karl]

Kai

Excellent coverage of how mother nature is changing our world in the manner that is most disturbing our senses. We humans do not like changes we have no manner in controling, but this is how we evolved and learnt to cope and manage evolution of the species being us..

My self have never had the opportunity to travel in your Alaska, it is so rugged to the senses and so varied in both wild life and terrain as to boggle the mind of a fellow that is the product of the North Sea.

Speaking for my self, I was very interested in the various photos you have kindly provided with much appreciation.

I do hope with trust, both the people of Alaska, wild life will adjust to these changing times that Mother Nature is presenting to us both withen our life times and those that will follow us..

Karl