Climate Change Blamed for Accelerated River Piracy Phenomenon

We blame climate change for a lot of the unusual phenomena we observe around us. However, this may be the strangest effect scientists have documented so far. On Monday, a panel of researchers published their conclusions on what they’re describing as the first case of large-scale river piracy. A trendy term, river piracy refers to the reorganization of a river’s course, regardless of the cause.

This time, it was human-caused climate change that redirected the vast stream of a large glacier in the Yukon territory, Canada. According to their research, the retreat of the glacier caused the meltdown to become drastically deflected from one river system to another. The changes cut down flow to the largest lake in Yukon. They also rechanneled the freshwater; instead of ending up in the Bering Sea, it now flows into the Pacific Ocean south of Alaska.

Accelerated River Piracy

This river piracy – as the researchers dubbed the reorganization – is something completely new. The team mentions such occurrences were quite frequent in the Earth’s geologic past, but it has never been documented as a present-day event. The rapidity of the event is the worrying factor. Researchers explained the changes happened “geologically instantaneous.”

Daniel Shugar, the leading author of the study and a researcher with the University of Washington at Tacoma, confessed his concern regarding the Slims River.

 “The river wasn’t what we had seen a few years ago. It was a faded version of its former self. It was barely flowing at all. Literally, every day, we could see the water level dropping, we could see sandbars popping out in the river.”

Shugar and his team observed glacial change caused the Slims River to lose much of its flow. Nature Geoscience originally published the study. Shugar has conducted the study in collaborations with researchers from six U.S. and Canadian universities. According to the results, the fact that the Slims River has chocked means the Kluane Lake lacks a steady incoming flow. As the largest body of water in the Yukon Territory, this lake’s well-being is crucial to the surrounding ecosystem.

In August 2016, the lake level was at a record low. Two small communities that depend on the lake’s water now have to adapt to the lower levels. Shugar worries that the Kluane Lake will continue to suffer losses and that the water level is likely to keep on dropping. If the lake level will decrease below its northern outlet, Kluane will become a “closed basin.” Such a change will cause alterations to the structure, the chemistry, and the biology of the lake.

Climate Change to Blame

The triggering event for the river piracy phenomenon occurred in summer 2016. The meltwater caused by the retreating Kaskawulsh glacier suddenly burst through a channel of ice, causing the glacial lake to drain. In turn, the waters of the Slims River ended up into a different river that runs in the Gulf of Alaska. These waters had previously headed toward the vast Yukon River, which flows on Alaska’s west coast.

river piracy

The picture above depicts the stream running along the toe of Kaskawulsh Glacier (Kluane National Park, Yukon). According to Shugar’s data, this channel suffered major modifications in 2016, allowing the glacier’s meltwater to seep in a different direction. Consequently, the Slims River water now flows into a different river system.

Data collected between 1956 and 2007 shoes the Kaskawulsh glacier has retreated by nearly half a mile during this period. The researchers stated that “constant climate” – the opposite of the climate change – couldn’t have caused the retraction of the Kaskawulsh glacier. The probability is “minuscule,” they say. The inference, therefore, is that the river piracy event is attributed to human-caused climate change.

In hydrologic terms, the Alsek River is the one benefiting from the change. Known for whitewater rafting, the Alsek has been experiencing far higher flows than normal. Consequently, it now empties into the Gulf of Alaska, which should see a high intake of freshwater.

Changes & Consequences

Shugar underscored the scale of the changes. It’s not just a freaky, climate change-linked occurrence. The Kaskawulsh glacier measures around 3 miles wide at its toe. The river it used to feed, the Slims River, featured a mile-wide floodplain and a steady flow. In turn, the lake that it fueled—Kluane Lake—is 45 miles long and over 250 feet deep in some spots. Now, due to the rerouting of the river, all of this will change.

The area is relatively wild, with sparse population, so large human populations will not suffer from the modifications. However, the events offer us a sense of just how sudden and drastic climate-related changes can be. Similarly, some mountain glacier shifts in the Bolivian Andes have recently upped the risk of dangerous outburst floods. This situation could seriously endanger the communities below them.

The current study illustrates the concept of “threshold response to warming.” According to Ken Tape, an Arctic ecologist at the University of Alaska, we shall see more of this. The Kaskawulsh glacier has been retreating for a while, but the river piracy occurred when it encountered a threshold in summer 2016. From that point on, the drainage changed abruptly in a matter of weeks, causing the downstream ecosystems to reorganize drastically.

Kluane River, Yukon Territory

Irreversible Modifications

Researchers cautioned that this glacier event is quite unique. When most glaciers retreat, they don’t cause such dramatic downstream consequences. The glacier mass balance dictates the flows increase or decrease, but rivers do not usually become rerouted in the process. Such changes are normally much more gradual. But even though the study’s case may be singular, it’s still a warning sign for future climate-related occurrences.

According to Shugar and other researchers, the glacier is less likely to flip back. In other words, the changes occurring to the river system that depends on it are irreversible, causing it to enter a new state. Preliminary estimates proved it is quite impossible for the Slims River to meet the requirements for returning to its original course. How many more permanent changes much happen before we do something about the accelerated climate change?

Image Credits: 1, 2, 3

Show Your Friends!
William E. Eubanks

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

Click Here to Leave a Comment Below 0 comments