GeoGarage blog

Wednesday, April 26, 2017

Climate change is making algal blooms worse

Blooming Gibraltar

NASA (acquired March 8, 2017)

From Nature by Daniel Cressey

Rising ocean temperatures drive more intense and longer lasting toxic outbreaks.

Researchers have long suggested that climate change could mean more damage from algal blooms — runaway growths of algae that can strangle marine ecosystems and devastate coastal economies.
Now, a study has unpicked how warming ocean temperatures have already driven an intensification of blooms around North America — the first time this link has been established at an ocean scale.

Harmful algal blooms can occur when changes in water conditions lead to a huge growth in the number of a particular species of algae.
The blooms can produce toxins, become so large that they kill marine life, and even turn water a different colour.

Research has established that one factor that helps blooms to spread is a sudden increase in nutrients such as nitrogen and phosphorus — often from agricultural fertilizers — and it has also linked warming temperatures to individual events.
But the broader influence of climate change on these outbreaks is less well quantified.

Turquoise Tendrils

NASA acquired March 18, 2017

Blooms abound

Christopher Gobler, who studies coastal ecosystems at Stony Brook University in Southampton, New York, and his colleagues looked at the relationship between blooms in the North Atlantic and North Pacific oceans and temperature changes in the region to investigate whether the events there were linked to were linked to ocean warming.
Previous research has studied the influence of climate change on algal blooms in individual coastal systems, says Gobler, but this is the first to assess ocean-basin-wide trends.

The researchers looked at two species of algae: Alexandrium fundyense and Dinophysis acuminata. (These species produce toxins that can cause illnesses — sometimes fatal — in humans who eat shellfish contaminated with them).
They used detailed data on sea-surface temperatures to model trends in the growth rates of the algae species and the periods when blooms occurred from the early 1980s into the twenty-first century.

The Treacherous and Productive Seas of Southern Africa

The light blue swirl to the east of Cape Agulhas is a phytoplankton bloom in an area of cool, upwelling water.

NASA acquired May 25, 2016

At dozens of sites, their model suggests that new blooms could occur where they hadn't happened before.
The researchers found higher potential growth rates and longer bloom seasons for both species in many parts of the Atlantic coast and along Alaska.
In some places, they found the bloom season to now be more than a month longer than it was in 1982.

The team used its model to retrospectively predict what harmful blooms might have occurred in the time period and found good agreement with actual events.
“What’s different about this study is they’re going beyond just saying 'Look, warmer is bad' and trying to do a rigorous quantitative analysis,” says Anna Michalak, who studies climate change and water quality at the Carnegie Institution for Science in Stanford, California.

Gobler points out that that the ocean does not warm uniformly, with some regions warming faster than average and some cooling.
This means blooms will appear in new regions, and may actually reduce in some places they currently occur.
Factors other than temperature are still clearly important, he says.

Many factors

Michalak points out that for events such as major droughts and floods, researchers can now often estimate how much more likely such events will be as a result of climate change.
But there is less research on the relationship between water quality and climate change.
“We don’t have that science on the water quality side,” she says, adding that this paper is one step in that direction.

In 2011, North America’s Lake Erie experienced one of its worst algal blooms in decades.
NASA acquired October 5, 2011

Sediment and Algae Color the Great Lakes

NASA acquired October 9, 2011

Michalak’s team has previously studied a massive 2011 bloom in Lake Erie — one of the largest ever on the Great Lake.
They pinned the event on a combination of weather conditions and agriculture putting huge nutrient loads in the lake.
That interplay of different factors is one reason why not everyone is yet prepared to say that climate change will necessarily lead to more harmful algal blooms.

Dynamic Spring Weather in North Atlantic Waters

NASA acquired May 14, 2015

Mark Wells, who studies harmful algal blooms at the University of Maine in Orono, points out that that rising temperatures alone may not always cause more harmful algal blooms.
In 2010 in the Gulf of Maine, he says, there were very high water temperatures, and many blooms were expected.
But in fact, water temperatures were so high that the layers of sea water became stratified and prevented mixing and the transfer of nutrients, so in the end there were fewer blooms than expected.
Still, he says, the latest study “provides a lot of new evidence” and represents a believable trend.

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Tuesday, April 25, 2017

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.”

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Monday, April 24, 2017

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.

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