SUD­DEN DEATH

How a ma­jor B.C. river dis­ap­peared in four days. And what it means for all of us

Canadian Wildlife - - BIGGER PICTURE - By Alanna Mitchell Il­lus­tra­tion by Pete Ryan

THE CASE CAP­TI­VATED SCI­EN­TISTS and head­line writ­ers when it be­came pub­lic last year: the Slims, a once mighty river in Yukon, had van­ished in just four days. It was the vic­tim of ge­o­log­i­cal theft.

While ge­ol­o­gists had plenty of an­cient ex­am­ples of what they call “river piracy,” a phe­nom­e­non in which the head­wa­ters of one river get stolen by an­other, they had never be­fore doc­u­mented it un­fold­ing in real time. More sur­pris­ing still, this one was “ge­o­log­i­cally in­stan­ta­neous,” wrote Daniel Shugar, the earth sci­en­tist at the Univer­sity of Wash­ing­ton in Ta­coma who de­tailed the thiev­ery in a 2017 pa­per for Na­ture Geo­science.

And while some sci­en­tists had pre­dicted the van­ish­ing act, they weren’t ex­pect­ing it just then. In fact, Shugar went to the south­west cor­ner of Yukon ter­ri­tory in the sum­mer of 2016 for the ex­press pur­pose of mea­sur­ing cur­rents in the Slims River. By the time he ar­rived in Au­gust, the Slims had prac­ti­cally dis­ap­peared.

He en­listed the help of col­leagues, in­clud­ing John Clague, who is Canada Re­search Chair in nat­u­ral haz­ard re­search at Si­mon Fraser Univer­sity in Van­cou­ver, to do a foren­sic in­ves­ti­ga­tion. The group sent drones over the area to take stock and looked at mea­sure­ments of the river’s flow over time.

The mys­tery re­volved around the mas­sive Kaskawulsh Glacier, part of Klu­ane Na­tional Park in the St. Elias Moun­tains, whose toe strad­dled a di­vid­ing line be­tween two wa­ter­sheds. On one side were the head­wa­ters of the south-flow­ing Kaskawulsh River. On the other, the north-flow­ing Slims, born nearly 200 years ago when the glacier be­gan block­ing an old river that had once drained south to the Pa­cific Ocean.

Then came cli­mate change, a ge­o­log­i­cally swift pulse of car­bon-based gases into the at­mos­phere from burn­ing fos­sil fuels. The Kaskawulsh Glacier be­gan to melt, los­ing both height and reach. From 1956 to 2007 alone, it re­treated 655 me­tres.

The cri­sis came in May 2016. Tem­per­a­tures that spring had been un­usu­ally warm. At the glacier, they were 3.6 de­grees Cel­sius warmer than the decade’s av­er­age — and that was likely the warm­est decade of the cen­tury. That led to a fast melt of the glacier’s sur­face, which prompted an ice-walled chan­nel to form at the Kaskawulsh River. Then the chan­nel be­gan to fall apart.

On May 26, the Slims be­gan a four-day col­lapse, its north-bound wa­ters rerouted south into the Kaskawulsh River and from there even­tu­ally the Pa­cific Ocean. By the end, the Slims was a mere trickle, never to re­grow. That sum­mer, the Slims floodplain be­came a dustbowl.

Why does the death of a river mat­ter? Many rea­sons. It af­fects the lakes and river­banks that de­pend on it, al­ter­ing wa­ter lev­els, sed­i­ment de­posit, chem­istry and the pop­u­la­tions of fish and other species that live there. It af­fects the peo­ple who use the river for recre­ation or food or mak­ing money or hy­dro­elec­tric­ity.

For ex­am­ple, be­cause Slims River died, wa­ter lev­els in Klu­ane Lake, Yukon’s big­gest body of wa­ter, have fallen by 1.7 me­tres. Now the wa­ter is so low that the pop­u­lar Canada Day fish­ing derby at Bur­wash Land­ing on the lake’s western shore has been can­celled. It’s too dan­ger­ous to launch boats.

And it mat­ters be­cause the Slims is not the only one. Other rivers are des­tined to suf­fer the same fate, Shugar and Clague ex­plain in an es­say for the Alpine Club of Canada’s 2018 State of the Moun­tains re­port. There’s a whole­sale ge­o­log­i­cal res­culpt­ing of the Earth un­der­way as glaciers, ice sheets and per­mafrost melt in this high-car­bon world we’ve made.

In North Amer­ica, that means more land­slides. It means newly un­frozen wa­ter raises sea lev­els. It means the land, now free from the weight of the glaciers, is ac­tu­ally lift­ing up. It means more vol­ca­noes as melt­ing ice un­cov­ers the tops of shal­low magma cham­bers.

Ul­ti­mately, it means changes in how we see the world around us. We’ve been schooled to think that some­thing as vast as a glacier or a river will be there for­ever. The theft of the Slims over just four days shows us that enor­mous change can hap­pen in the blink of an eye.

This rapid change is what cli­mate sci­en­tists some­times re­fer to as a tip­ping point, or a regime change. Ev­ery­thing’s go­ing along the same… un­til it isn’t. It’s like your fin­ger press­ing on a light switch: one nanosec­ond the light is off; the next it’s on.

The les­son here is that na­ture has a mind of her own. You can push her only so far un­til she changes course, like a river that is there one day and gone the next.1

IN MAY 2016, THE SLIMS RIVER SLOWED TO A TRICKLE, THEN DIED. WITHIN A FEW MONTHS, ITS FLOODPLAIN WAS A DUSTBOWL

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