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Flooded out

Rising lake levels in the McMurdo Dry Valleys affect science, field camps

 

It’s certainly not a flood of biblical proportions, but rising lake levels and pulses of flooding events in the McMurdo Dry Valleys are threatening established field camps — and could eventually change the nature of the cold desert ecosystem.

After what appears to have been a decade or so of aberrant cooling until the early 2000s, the Dry Valleys seem to have resumed a long-term trend of warming, according to John Priscu, a professor of ecology at Montana State University in Bozeman and an expert on the ice-covered lakes.
“They’re roughly changing together, although Lake Bonney, because of its steep sides and water input from the Taylor Glacier, is rising the fastest,” said Priscu of the three major lakes in the Taylor Valley, which harbors the most studied lakes of the ice-free valleys.
The McMurdo Dry Valleys have been the site of a Long Term Ecological Research (LTER) program beginning in 1993, though scientists have conducted studies there since the late 1950s. The exploration of the valleys, which sit at the edge of the massive East Antarctic Ice Sheet, dates back even further, to the turn of the 20th century, when Briton Robert F. Scott led an expedition through the region.
In fact, thanks to Scott, whose team in 1903 measured a section of Lake Bonney, the westernmost lake in Taylor Valley, scientists today are able to extrapolate its growth during the intervening decades.
Between 1903 and 1973, when systematic monitoring began, the lake level rose about 12 meters, representing a 4 percent per year increase in flow, according to Diane McKnight, a professor at the University of Colorado at Boulder and the principal investigator for the McMurdo Dry Valleys LTER.
Lake Bonney appears to be rising faster than either Lake Fryxell or Lake Hoare to the east, partly due to its proximity to the Taylor Glacier. In fact, scientists have discovered that the glacier itself is adding water to the lake, which is about seven kilometers long and up to 900 meters wide. A narrow channel — the place where Scott’s men conducted their survey — separates the lake into east and west lobes.
“The Taylor Glacier is doing some very strange things. It’s adding a lot of water,” said Priscu, who has made 27 trips down to the Antarctic since 1983. “It’s gaining water from melting underneath.”
A field camp built in 1988 on the shores of Lake Bonney to support Priscu’s early research is slowly being moved to higher ground until a new facility is eventually constructed, according to Woody Haywood, who oversees the planning and building of science field camps for the U.S. Antarctic Program (USAP).
 
“About four years ago, it became painfully obvious that the trend was such that at Lake Bonney the water was rising at something measurable, and we’d soon have to address it,” Haywood said.
 
Over the last several years, the science construction team has removed two labs and replaced them with larger structures away from the shore. Haywood said the National Science Foundation (NSF), which manages the USAP, has initiated planning for new camps at Bonney and Fryxell, which is also being threatened by higher water levels.

“Both of those camps have small, restrictive lab space compared to the new ones that we’re designing and what we’ve been experimenting with at Lake Hoare,” Haywood said.

For scientists like Diana Wall, a professor at Colorado State University and a co-PI on the McMurdo Dry Valleys LTER, the periodic floods have played havoc with some of her experiments, which focus on the biodiversity in the valleys’ cold soils. Her research involves studying how microscopic critters, such as the wormlike nematode, might respond to a changing climate.

“All of us are seeing much more connectivity between the glaciers, the steams, the lakes,” Wall said. “It’s like one big hydrologic cycle, and all of a sudden it’s tying everything together.”
 
Flooding hasn’t been restricted to the Taylor Valley. The Onyx River in Wright Valley to the north has flowed at speeds upwards of 700 cubic feet per second in recent years.
“That’s a real river, which in a very cold place like this, represents a lot of melt,” McKnight said.
A water-dominated system would not just affect soil biodiversity, but also biodiversity in the lakes.
Priscu predicts that if the current trends continue, the biogeochemistry of the entire ecosystem would change as the water engulfs more of the valley. In 100 years, Lake Fryxell would merge with Lake Hoare. In two centuries, Lake Bonney would flow east and coalesce with Fryxell and Hoare. In less than a millennium, the lake would fill the valley and drain into McMurdo Sound.
“When they starting merging again, the biodiversity is going to smear out,” he said. “We’re going to lose these unique organisms.”
It wouldn’t be the first time such a lake existed. Scientists have suggested that a proglacial lake, formed by the retreat of a glacier, filled the valley to a much larger extent at the end of the last ice age.
It’s also not the first time rising lake levels have prompted a field camp move. A new facility was built at Lake Hoare in the mid-1990s when it became the main gateway camp for the LTER program. The original camp from the 1980s was small — just a single lab, a storage building, and a Korean-era building known as a Jamesway that served as the kitchen and social center of the facility.
However, the old camp wasn’t removed until this past field season, as the lake began to rise again in earnest over the last couple of years after idling for nearly a decade, according to Haywood.  
“It was obvious that it was time to move it,” he said.
The Jamesway, which had still been used for storage, was relocated to the current camp onto a timber foundation. “The ‘newer’ Hoare camp should be fine for quite a few years to come,” Haywood said.
For more than a decade, from the late 1980s into the early 2000s, the Dry Valleys were actually cooling. The LTER researchers even published a paper in the journal Nature in January 2002 showing the cooling trend, which caused a drop in stream flow and an increase in lake ice thickness. However, the following season, a major flood swept through the Taylor Valley, increasing lake levels by more than a meter.
Priscu said that the cooling trend has been shown to be influenced by ozone depletion in the stratosphere, which researchers believe affected circulation patterns in the lower troposphere. Basically, a cold high-pressure system settled over the region during the period of cooling, shielding it from warmer air.
But as the ozone layer slowly heals, the atmospheric patterns appear to be returning to pre-ozone trends, according to Priscu. That means more grey but warmer days ahead.
“Things are changing. They’re changing right in front of us,” Priscu said. “What we’re studying is pushing us out — we’re studying climate change.”
NSF-funded research in this story: Diane McKnight, University of Colorado at Boulder; John Priscu, Montana State University in Bozeman; and Diana Wall, Colorado State University; Award No. 1115245.
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Curator: Peter Rejcek, Antarctic Support Contract | NSF Official: Winifred Reuning, Division of Polar Programs