Receding glacier causes immense Canadian river to vanish in four days

A view of the ice canyon that now carries meltwater from the Kaskawulsh glacier, seen here on the right, away from the Slims river and toward the Kaskawulsh river.

Photograph: Dan Shugar/University of Washington Tacoma

From The Guardian by Hannah Devlin

First ever observed case of ‘river piracy’ saw the Slims river disappear as intense glacier melt suddenly diverted its flow into another watercourse 

An immense river that flowed from one of Canada’s largest glaciers vanished over the course of four days last year, scientists have reported, in an unsettling illustration of how global warming dramatically changes the world’s geography.

 One of Canada's rivers has vanished.
The Slims river has been flowing through Canada for 300 years, but in 2016 something happened that caused it to vanish in the blink of an eye.
In just four days, the river dipped in height so much that it could not recover.

Today, the only evidence of the Slims river is its empty, thirsty channel.
Scientists attribute the river's disappearance to our warming climate and predict that future rivers may suffer the same fate.

The abrupt and unexpected disappearance of the Slims river, which spanned up to 150 metres at its widest points, is the first observed case of “river piracy”, in which the flow of one river is suddenly diverted into another.

The mouth of the Slims River at Kluane Lake

For hundreds of years, the Slims carried meltwater northwards from the vast Kaskawulsh glacier in Canada’s Yukon territory into the Kluane river, then into the Yukon river towards the Bering Sea.
But in spring 2016, a period of intense melting of the glacier meant the drainage gradient was tipped in favour of a second river, redirecting the meltwater to the Gulf of Alaska, thousands of miles from its original destination.

The continental-scale rearrangement was documented by a team of scientists who had been monitoring the incremental retreat of the glacier for years.
But on a 2016 fieldwork expedition they were confronted with a landscape that had been radically transformed.

The retreat of the Kaskawulsh glacier has resulted in a drastic change in the destination of its meltwater

“We went to the area intending to continue our measurements in the Slims river, but found the riverbed more or less dry,” said James Best, a geologist at the University of Illinois.
“The delta top that we’d been sailing over in a small boat was now a dust storm. In terms of landscape change it was incredibly dramatic.”

Climate change is causing thick ice deposits that form along Arctic rivers to melt nearly a month earlier than they did 15 years ago, a new study finds.

In the past, river icings have melted out around mid-July, on average.

But a new study measuring the extent of river icings in the U.S. and Canadian Arctic shows most river icings disappeared 26 days earlier, on average, in 2015 than they did in 2000, melting around mid-June.

In addition, the study found most icings that don’t completely melt every summer were significantly smaller in 2015 than they were in 2000.

Dan Shugar, a geoscientist at the University of Washington Tacoma and the paper’s lead author, added: “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 team flew a helicopter over the glacier and used drones to investigate what was happening in the other valley, which is less accessible.
“We found that all of the water that was coming out from the front of the glacier, rather than it being split between two rivers, it was going into just one,” said Best.

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.

Photograph: Jim Best/University of Illinois

While the Slims had been reduced to a mere trickle, the reverse had happened to the south-flowing Alsek river, a popular whitewater rafting river that is a Unesco world heritage site.
The previous year, the two rivers had been comparable in size, but the Alsek was now 60 to 70 times larger than the Slims, flow measurements revealed.
The data also showed how abrupt the change had been, with the Slims’ flow dropping precipitously from the 26 to 29 May 2016.

Geologists have previously found evidence of river piracy having taken place in the distant past.
“But nobody to our knowledge has documented it happening in our lifetimes,” said Shugar
 “People had looked at the geological record, thousands or millions of years ago, not the 21st century, where it’s happening under our noses.”

A satellite image of the Kaskawulsh glacier and Slims and Kaskawulsh rivers.

The yellow lines represent the pre-2016 flow direction of the Slims and Kaskawulsh rivers.

Daniel Shugar / University of Washington

Prof Lonnie Thompson, a paleoclimatologist at Ohio State University who was not involved in the work, said the observations highlight how incremental temperature increases can produce sudden and drastic environmental impacts.
“There are definitely thresholds which, once passed in nature, everything abruptly changes,” he said.

Between 1956 and 2007, the Kaskawulsh glacier retreated by 600-700m. In 2016, there was a sudden acceleration of the retreat, and the pulse of meltwater led to a new channel being carved through a large ice field.
The new channel was able to deliver water to the Alsek’s tributary whose steeper gradient resulted in the Slims headwater being suddenly rerouted along a new southwards trajectory.

In a geological instant, the local landscape was redrawn.
Where the Slims once flowed, Dall sheep from Kluane National Park are now making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted.
The formerly clear air is now often turned into a dusty haze as powerful winds whip up the exposed riverbed sediment.
Fish populations are being redistributed and lake chemistry is being altered.
Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now further from shore.

Sections of the newly exposed bed of Kluane Lake contain small pinnacles.

Wind has eroded sediments with a harder layer on top that forms a protective cap as the wind erodes softer and sandier sediment below.

These pinnacles, just a few centimeters high, are small-scale versions of what are sometimes termed “hoodoos.”

Photograph: Jim Best/University of Illinois

A statistical analysis, published in the journal Nature Geoscience, suggests that the dramatic changes can almost certainly be attributed to anthropogenic climate change.
The calculations put chance of the piracy having occurred due to natural variability at 0.5%.
“So it’s 99.5% that it occurred due to warming over the industrial era,” said Best.

The Yukon region is extremely sparsely inhabited, but future river piracy could have catastrophic effects on towns, villages and ecosystems that have sprung up around available water, according to an analysis accompanying the paper, by Rachel Headley, a geologist at the University of Wisconsin-Parkside.
“If a river changes course so drastically that the drainage basin no longer reaches its original outlet, this change might eventually impact human and biological communities that have grown around the river’s original outlet,” she said.

Thompson, who has documented glacial retreat on Mount Kilimanjaro, predicts that there will be an acceleration in the observations of river piracy events as glaciers retreat globally.
“I think we could see similar divergence in streams in the Himalayas as well as throughout the Third Pole region, the Andes of Peru, other sites in northern Canada and Alaska,” he said.
“Often these events occur in remote and poor parts of our planet and thus go largely unnoticed by the larger population but greatly impact the livelihood of many families downstream.”

Links :

• The Guardian : Rivers vanishing into thin air: this is what the climate crisis looks like /
  Glacier melt shows a climate change tipping point. We must pay attention / Collapsing Greenland glacier could raise sea levels by half a metre, say scientists
• Vox : In 4 days, a river that had flowed for millennia disappeared
• Futurity : Melting glacier leads to first modern ‘river piracy’
• AGU : Arctic river ice deposits rapidly disappearing
  
  

The mysteries of the first-ever map of the North Pole

  The second draft of the Septentrionalium Terrarum, released in 1606.

Gerardus Mercator/Public Domain

From Atlas Obscura by by Cara Giaimo

Gerard Mercator’s 16th-century attempt at mapping the Arctic includes such guesses as a giant whirlpool and polar pygmies. 

These days, climate scientists are looking hard at Arctic maps.
As winter sea ice shrinks and cracks appear, they try to understand the reasons for these changes, and determine what we should expect in the future.
Centuries ago, though, when people tried to map the Arctic, they weren’t too concerned with what was happening to it—they just wanted to know what the heck was up there.
And, if they didn’t know, they pretty much made it up.
Such was the case with the first known map of the Arctic: the Septentrionalium Terrarum, which is filled with magnetic stones, strange whirlpools, and other colorful guesses.

The map’s creator, the Flemish cartographer Gerardus Mercator, is best known for the “Mercator projection,” the now-famed method of taking the curved lines of the Earth and transforming them into straight ones that can be used on a flat map.
The Mercator projection was invented for sailors, who, thanks to its design, could use it to plot a straight-line course from their point of origin to their destination.
In 1569, Mercator came out with a map of the world based on this principal, which stretched from East to West and promised, in his words, “no trace… of any of those errors which must necessarily be encountered on the ordinary charts of shipmasters.”

In order to make his map useful for navigation, though, Mercator had to sacrifice accuracy in other areas—specifically, he had to stretch out the top and bottom parts of his map, making the lands and seas in the far North and South appear disproportionately larger than those nearer the equator.
(This is also why so many people think Africa is the same size as Greenland, when it is really about 14 times bigger—the Mercator projection is still very common in schools.)

 Mercator’s 1569 map of the world, the first to feature his famous projection.

The Arctic inlet is on the bottom left. Gerardus Mercator/Public Domain

Under the terms of this Mercator math, the North Pole would appear so large as to be almost infinite.
So instead of including it in the overall projection, Mercator decided to set a small, top-down view of the Arctic in the bottom left corner of his world map.
Geographical historians consider this to be the first true map of the Arctic.
Over the subsequent decades, as new information came to light, Mercator and his protégés enlarged and updated this original map—the draft above is an attempt from 1606, updated by his successor, Jodocus Hondius—but those original bones remained in place.

By the 1500s, not very many people had ventured up to the Arctic—no explorer would set foot on the Pole itself until 1909.
This didn’t stop Mercator, who dug into some dicey sources to suss out what he should include. The most influential, called Inventio Fortunata (translation: “Fortunate Discoveries”) was a 14th-century travelogue written by an unknown source; in Mercator’s words, it traced the travels of “an English minor friar of Oxford” who traveled to Norway and then “pushed on further by magical arts.”
This mysterious book gave Mercator the centerpiece of his map: a massive rock located exactly at the pole, which he labels Rupus Nigra et Altissima, or “Black, Very High Cliff.”

 At the time, many assumed the pole itself featured a giant, magnetic mountain.

The presence of this formation was widely accepted at the time.
Most people thought it was magnetic, which provided an easy explanation for why compasses point north.
But Mercator was not quite convinced by this argument, and included a different rock, which he labels “Magnetic Pole,” in the top left corner of the map, just north of the Strait of Anián.

Mercator draws the Arctic in four large chunks separated by channels of flowing water, which meet in the middle in a giant whirlpool. He got this idea from two 16th-century explorers, Martin Frobisher and James Davis, who each made it as far as what is now Northern Canada. Both documented their experiences with vicious currents, which, they wrote, pulled giant icebergs along like they were nothing. “Without cease, it is carried northward, there being absorbed into the bowels of the Earth,” Mercator wrote on his original map.

 The supposed home of “Pygmeis.”

Each piece of the Arctic also has particular qualities.
According to Mercator’s labels, the one in the lower right is supposedly home to “pygmies, whose length is four feet”—likely another reference to the Inventio Fortunata, which described groups of small-statured people living in the polar regions.
(It’s possible that the author of the Inventio was referring to the indigenous inhabitants of Lapland.)
The one next door, on the bottom left, is apparently “the best and most salubrious” of all the chunks, although no evidence is given to support this—or to explain why the pygmies wouldn’t want to live there, instead.

After Mercator died in 1594, explorers continued to gain new knowledge of the Arctic, and cartographers revised their view of both Poles.
By 1636, up-to-date maps of the region lacked Mercator’s four regions, along with the Rupus Nigra and the central whirlpool.
Instead, they showed one large piece of land, surrounded by smaller islands and, often, adorned with the ship’s routes that enabled this geographical knowledge in the first place.
As we peer at modern Arctic maps, wondering what changes are ahead, it’s fascinating to think back to Mercator’s original version, mysterious and broken from the beginning.

Links :

• GeoGarage blog : Gerardus Mercator : father of modern mapmaking / The end of the map : why the World looks the way it does / 5 maps that help explain the Arctic

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Ben Thouard, photograph of virgin waves 
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Links :

• People's choice winner of the 2017 WSSF - Olympus Pro Photographer Showdown - Whistler - BC 

Diving down to the deep ocean

Even in the perpetual darkness of the deepest ocean, scientists discover the discarded rubbish of modern life.

The pristine Arctic has become a garbage trap for 300 billion pieces of plastic

 Here’s a map the researchers provided, showing the ocean circulation in the Atlantic and where that, in turn, has delivered plastic particles:
Locations and plastic concentrations of the sites sampled.

The white area shows the extension of the polar ice cap in August 2013, and green curves represent the North Atlantic Subtropical Ocean Gyres and the Global Thermohaline Circulation poleward branch.

(Andres Cozar)

 From The Washington Post by Chris Mooney

Drifts of floating plastic that humans have dumped into the world’s oceans are flowing into the pristine waters of the Arctic as a result of a powerful system of currents that deposits waste in the icy seas east of Greenland and north of Scandinavia.
In 2013, as part of a seven-month circumnavigation of the Arctic Ocean, scientists aboard the research vessel Tara documented a profusion of tiny pieces of plastic in the Greenland and Barents seas, where the final limb of the Gulf Stream system delivers Atlantic waters northward.
The researchers dub this region the “dead end for floating plastics” after their long surf of the world’s oceans.
The researchers say this is just the beginning of the plastic migration to Arctic waters.
“It’s only been about 60 years since we started using plastic industrially, and the usage and the production has been increasing ever since,” said Carlos Duarte, one of the study’s co-authors and director of the Red Sea Research Center at the King Abdullah University of Science and Technology in Saudi Arabia.
“So, most of the plastic that we have disposed in the ocean is still now in transit to the Arctic.”

A seal lies on an iceberg in front of the research vessel Tara.

The nonprofit organization Tara Expeditions has been active since 2003, sailing across the world's oceans to study biodiversity, the impacts of climate change and other research topics. In 2013, the schooner sailed around the Arctic Ocean to collect plastic debris floating in the water.
photo : Anna Deniaud / Tara Expeditions Foundation

The results were published Wednesday in the journal Science Advances.
The study was led by Andrés Cózar of the University of Cádiz in Spain along with 11 other researchers from universities in eight nations: Denmark, France, Japan, the Netherlands, Saudi Arabia, Spain, the United Kingdom and the United States.
The researchers estimated that about 300 billion pieces of tiny plastic are suspended in these Arctic waters right now, although they said the amount could be higher.
And they think there is even more plastic on the seafloor.

 Tara Oceans expedition route

Several factors support the idea that the plastic entered these waters via ocean currents rather than local pollution.
First, the Arctic has a very small population that is unlikely to directly contribute so much waste. Also, the aged and weathered state of the plastic, and the tiny size of the pieces found, suggested that it had traveled the seas for decades, breaking down along the way.
“The plastic pieces that may have been initially inches or feet in size, they have been brittled by exposure to the sun and then fragmented into increasingly smaller particles, and eventually led to this millimeter-size plastic that we call microplastic,” Duarte said.
“That process takes years to decades. So the type of material that we’re seeing there has indications that it has entered the ocean decades ago.”

 Manta net used to collect microplastics

© Anna Deniaud / Tara Expeditions Foundation

Finally, the study didn’t find much plastic in the rest of the Arctic ocean beyond the Greenland and Barents seas, also suggesting that currents were to blame.
Instead the plastic had accumulated where the northward-flowing Atlantic waters plunge into the Arctic depths. Presumably, the plastic then lingers at the surface.
The Greenland and Barents seas contained 95 percent of the Arctic’s plastic, the research found (the ship sampled 42 sites across the Arctic Ocean).
The Barents Sea happens to be a major fishery for cod, haddock, herring and other species.
A key question will be how the plastic is affecting these animals.
Here’s a collage that the researchers provided showing the types of plastic they found:

 Photo collage of plastic fragments found in the Arctic Ocean.

Although plastic debris was scarce in most of the Arctic waters, it reached high concentrations in areas of the Greenland and Barents seas. (Credit: Andres Cozar)

The study’s results sent a troubling message to one researcher who has also focused on the consequences of plastic debris in the oceans and other waterways.
“Isn’t it kind of ironic that days before Earth Day there is more demonstrated proof of widespread contamination of our plastic waste in places that are so far from the human footprint and thus locations we consider to be pristine,” said Chelsea Rochman, a marine ecologist at the University of Toronto who was not involved in the study but praised it as “a great contribution to the field.”
The ocean circulation system in the Atlantic responsible for this plastic transport is part of a far larger “thermohaline” ocean system driven by the temperature and salt content of oceans.
It is also often called an “overturning” circulation because cold, salty waters sink in the North Atlantic and travel back southward at deep ocean depths.

Tara expedition

As humans now put 8 million tons of plastic in the ocean annually, learning how such currents affect the plastic’s global distribution is a key scientific focus.
Researchers, including Duarte, previously found that plastic slowly travels the world’s oceans but tends to linger in five “gyres,” or circular ocean currents in the subtropical oceans in both the northern and southern hemispheres.
One of those gyres is located in the Atlantic, which then feeds the Arctic.

 Aurora, a three-year-old polar bear, was found with her sister in the Arctic Ocean in May 2010 and brought to the Royev Ruchey Zoo in Siberia.

photo : Ilya Naymushin / Reuters

Scientists noted that the vast majority of ocean plastic becomes lost before it reaches the Arctic.
They aren’t sure where most of the plastic falls out and are researching to determine those locations.
“The plastic that escapes those traps is the one that actually makes it into the Arctic,” Duarte said.
“But when it enters the Arctic, there is no way out, it just stays there and is stuck there.”
Because it takes such a long time for plastic to travel across the world in ocean currents, the study concludes that the current waste is largely the work of North Americans and Europeans, who dumped it in the Atlantic.
Waste from other parts of the world that dump huge volumes of plastic into the oceans is still in transit.
Rochman said she feared that as the Arctic becomes more accessible because of ice melt linked to climate change, more plastic could wash in.
“As the ice melts, we may see increasing concentrations of plastic in the Arctic due to the opening of passageways for vessels and plastics in surface currents,” she said, “as well as plastics in the ice becoming free to float and interact with marine animals upon melting.”

Links :

• NYTimes : Questions for: ‘Trillions of Plastic Bits, Swept Up by Current, Are Littering Arctic Waters’
• The Verge : A big patch of plastic garbage has been discovered in the Arctic
• Mashable : A 'conveyor belt' of plastic is polluting the Arctic Ocean