"It's not just climate change that is causing the rapid loss of ice in the West Antarctic; researchers have discovered that geothermal activity is contributing to the melting."
"Antarctica is a land of ice. But dive below the West Antarctic Ice Sheet, and you'll find fire as well, in the form of subglacial volcanoes.
Now, a new study finds that these subglacial volcanoes and other geothermal "hotspots" are contributing to the melting of Thwaites Glacier, a major river of ice that flows into Antarctica's Pine Island Bay. Areas of the glacier that sit near geologic features thought to be volcanic are melting faster than regions farther away from hotspots, said Dustin Schroeder, the study's lead author and a geophysicist at the University of Texas at Austin.
This melting could significantly affect ice loss in the West Antarctic, an area that is losing ice quickly.
Antarctic heat
Researchers have long known that volcanoes lurk under the ice of West Antarctica. This is a seismically active region, where East and West Antarctica are rifting apart. In 2013, a team of scientists even found a new volcano beneath the West Antarctic Ice Sheet.
West Antarctica is also hemorrhaging ice due to climate change, and recent studies have suggested there is no way to reverse the retreat of West Antarctic glaciers. However, the timing of this retreat is still in question, Schroeder said — it could take hundreds of years, or thousands. It's important to understand which, given that meltwater from the West Antarctic Ice Sheet contributes directly to sea level rise.
Scientists use computer models to try to predict the future of the ice sheet, but their lack of understanding of subglacial geothermal energy has been a glaring gap in these models. Measuring geothermal activity under the ice sheet is so difficult that researchers usually just enter one, uniform estimate for the contributions of geothermal heat to melting, Schroeder said.
Of course, volcanism isn't uniform. Geothermal hotspots no doubt influence melting more in some areas than in others.
"It's the most complex thermal environment you might imagine," study co-author Don Blankenship, a geophysicist at UT Austin, said in a statement. "And then, you plop the most critical dynamically unstable ice sheet on planet Earth in the middle of this thing, and then you try to model it. It's virtually impossible.".
Hotspots melting.
To unravel the complexity, the researchers built on a previous study they published in 2013 that mapped out the system of channels that flows beneath the Thwaites Glacier, a fast-flowing glacier that scientists say is vulnerable to global warming.Using data from airborne radar, the researchers were able to figure out where these subglacial streams were too full to be explained by flow from upstream. The swollen streams revealed spots of unusually high melt, Schroeder said. Next, the researchers checked out the subglacial geology in the region and found that fast-melting spots were disproportionately clustered near confirmed West Antarctic volcanoes, suspected volcanoes or other presumed hotspots.
"There's a pattern of hotspots," Schroeder said. "One of them is next to Mount Takahe, which is a volcano that actually sticks out of the ice sheet."
The minimum average heat flow beneath Thwaites Glacier is 114 milliwatts per square meter (or per about 10 square feet) with some areas giving off 200 milliwatts per square meter or more, the researchers report today (June 9) in the journal Proceedings of the National Academy of Sciences. (A milliwatt is one-thousandth of a watt.) In comparison, Schroeder said, the average heat flow of the rest of the continents is 65 milliwatts per square meter.
"It's pretty hot by continental standards," he said.
The extra melt caused by subglacial volcanoes could lubricate the ice sheet from beneath, hastening its flow toward the sea, Schroeder said. To understand how much the volcanic melt contributes to this flow — and what that means for the future of the West Antarctic Ice Sheet — glaciologists and climate scientists will have to include the new, finer-grained findings in their models. Schroeder and his colleagues also plan to expand their study to other glaciers in the region.
"Anywhere in the West Antarctic Ice Sheet is going to be a candidate for high melt areas," he said. "And we have radar data covering much of it."
"Editor's Note: This article was updated to reflect the fact that airborne data, not satellite information, was used in the study."
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5/12/14, "Catastrophic Collapse of West Antarctic Ice Sheet Begins," Live Science, Betsy Oskin
"Rising seas"
"The good news is that sea-level rise will be relatively small in the coming centuries, according to the Thwaites Glacier model published today in the journal Science.
"Over the next few centuries, the rate of sea level rise will be pretty moderate," said lead study author Ian Joughin, a glaciologist at the University of Washington's Applied Physics Laboratory."...
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11/17/13, "Active Volcano Discovered Under Antarctic Ice Sheet," Live Science, Betsy Oskin
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| Mount Sidley |
an active volcano hidden beneath the massive ice sheet, researchers
said today (Nov. 17) in a study published in the journal Nature
Geoscience.The discovery finally confirms long-held suspicions of volcanic activity concealed by the vast West Antarctic Ice Sheet. Several volcanoes poke up along the Antarctic coast
and its offshore islands, such as Mount Erebus, but this is the first
time anyone has caught magma in action far from the coast.
"This is really the golden age of discovery of the Antarctic continent," said Richard Aster, a co-author of the study and a seismologist at Colorado State University. "I think there's no question that there are more volcanic surprises beneath the ice."
The volcano was a lucky find. The research project, called POLENET, was intended to reveal the structure of Earth's mantle, the layer beneath the crust. In 2010, a team led by scientists from Washington University in St. Louis spent weeks slogging across the snow, pulling sleds laden with earthquake-monitoring equipment.
Right place, right time
Two earthquake swarms struck beneath the researchers' feet
in January 2010 and March 2011, near the Executive Committee Range in
the Marie Byrd Land region of the continent. As the researchers later discovered,
the tremors — called deep, long-period earthquakes (DLPs) — were nearly
identical to DLPs detected under active volcanoes in Alaska and
Washington. The swarms were 15 to 25 miles (25 to 40 kilometers) below
the surface."It's an exciting story," said Amanda Lough, the study's lead author and a graduate student in seismology at Washington University in St. Louis. Though there were no signs of a blast, a 3,200-foot-tall (1,000 meters) bulge under the ice suggests the volcano had blasted out lava in the past, forming a budding peak.
"We can say with pretty high confidence that there wasn't an eruption while we were out there," Lough told LiveScience's OurAmazingPlanet. "We had people installing [seismometer] stations and flying airborne radar over the ice. But from the bed topography, we can see there is something building up beneath the ice."
Scientists think that underground magma and fluids pushing open new paths and fracturing rock cause deep, long-period earthquakes. Many active volcanoes in Alaska's Aleutian Islands
have frequently produced these deep earthquake swarms without any signs
of impending eruptions.However, researchers also monitor the tremors because a sudden uptick in shaking was seen before eruptions at Mount Spurr and Mount Redoubt in Alaska.
A volcanic flood
If the volcano in Antarctica did erupt, it would melt the bottom of the ice sheet immediately above the vent. Scientists aren't sure what would happen next. In Iceland, volcanic eruptions can melt glaciers, causing massive floods called jökulhlaups. But the ice above the Antarctic volcano is more than a half-mile (1 km) thick....
A geologic puzzle
Signs of active and extinct volcanoes pop up all over Antarctica. Ash layers and lava indicate volcanoes spouted while the continent froze during the past 20 million years or more. (An 8,000-year-old ash layer sits above the newly found volcano, but it comes from Mount Waesche, a nearby peak.)...
The earthquake swarms line up with older volcanoes in the Executive Committee Range, suggesting the volcanic activity there is slowly migrating south by 6 miles (9.6 km) every million years. This migration is perpendicular to the motion of Antarctica's tectonic plate, so a hotspot or mantle plume is not feeding the volcanoes, Lough said. (A mantle plume should make volcanoes that line up parallel to plate motion, like those of the Hawaiian Islands.)
The big mystery is figuring out why the volcano and its forerunners even exist. "Antarctica is certainly one of the most fascinating and enigmatic of all of Earth's continents," Aster said.
Let's set the scene. Antarctica is split by an incredible mountain range. Imagine if Utah's spectacularly steep Wasatch Mountains cleaved North America from Texas all the way to Canada.
That's what the Transantarctic Mountains are like. In the West, the land dives off into a deep rift valley, where the crust has been tearing apart for about 100 million years. The newly found volcano sits on the other side of this rift, in a higher-elevation region called Marie Byrd Land.
While the torn crust may seem like the best explanation for Antarctica's many volcanoes, many of the peaks fit no obvious pattern. Rifting and volcanism in Antarctica could be like nowhere else on Earth.
"What is going on with the crust in Antarctica is still puzzling," Lough said."
Image: "Mount Sidley is the youngest volcano rising above the ice in West Antarctica's Executive Committee Range. A group of seismologists has detected new volcanic activity under the ice about 30 miles ahead of Mount Sidley. Credit: Doug Wien"=======================
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