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A river in Canada just turned to piracy because of global warming

A river in Canada just became a victim of piracy. River piracy.

Yes, one river straight-up stole another river’s water, with a
swashbuckling assist from a melting glacier and
the unique landscape of the area deep in the Yukon.

In a paper
published in Nature Geoscience geomorphologists
describe how the Slims river—which normally flows north—was
abruptly cut off from its water supply. Now all that water
feeds a totally different river—the Kaskawulsh—which flows
south.

The researchers didn’t expect to observe a case of river piracy
when they went to investigate the area.

“Our goal was to look at how this glacial river [the Slims]
adjusts over the course of a year,” says study co-author Dan
Shugar. “We certainly didn’t expect it to be totally gone.”

But when Shugar and his colleagues went into the field, that’s
exactly what they found. Where the Slims river once flowed,
only a shallow lake remained.

Shugar and his co-authors decided to figure out why, so they
headed to the river’s source, the Kaskawulsh glacier. As the
massive sheet melts, it feeds huge rivers like the Slims and
the Kaskawulsh, which join up with even longer rivers. But it
wasn’t feeding the Slims anymore.

River piracy—which ranks among the coolest technical terms in
the world—happens when water from one river or stream gets
co-opted by another river. Usually, it’s seen in the geologic
record, as a river carves a different path through soil and
stones, but not in real-time. This particular instance of river
piracy is fairly unique. It only happened because the glacier
which fed the rivers was located in just the right place.

The glacier sits directly on the border between the two
drainage basins, which is why it was able to supply water to
both rivers for so long. But now, the glacier had retreated,
melting in the face of climate change. In it’s smaller shape,
it occupies a slightly different footprint in the mountains,
and meltwater that was once divided equitably is now primarily
diverted to the Kaskawulsh river instead.

Specifically, a lake right at the toe of the glacier, Slims
lake, was able to melt its way through the ice of the glacier
towards the Kaskawulsh river basin. That issued a death
sentence for the Sims river. “It was beheaded, if you will”
Shugar says.

And there’s no coming back from a beheading.

“For the Slims lake to re-establish a hydrologic connection
with the Slims river would require the glacier to advance, and
that’s unlikely to happen in the current climate,” Shugar says.

Now the Slims river will have to cope with much-reduced flows,
while the white waters of the Kaskawulsh river will be stronger
as both river systems try to adjust to the new normal.

Shugar says that this sudden change in river flows can be
directly linked to
human-caused climate change
. The melting of these glaciers,
Shugar says, is happening much
faster than can be explained by natural causes
.

“Climate change is happening. And it’s not just happening over
there, in some other place. It’s happening here in North
America, and some of the consequences can be very rapid and
might not always be what we were expecting,” Shugar says.

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