Archive for the ‘glacier’ Category

Glaciers in Antarctica are being melted not only by warmer ocean waters but also by underwater volcanoes, a change in our basic understanding of what’s happening underneath West Antarctica’s ice sheet, scientists say.

Geothermal heat from underneath is helping melt the region’s Thwaites Glacier, in the headlines recently for its rapid melt and retreat, researchers at the University of Texas at Austin say.

Scientists in the university’s Institute for Geophysics say they used ice-penetrating radar aboard aircraft to find significant geothermal heat sources — hotter and spread over a broader area than previously thought — underneath the glacier.

Caused by magma moving underground and volcanic activity associated with that movement, geothermal heat might represent a significant factor in changing the stability of the ice mass above, they researchers reported in the Proceedings of the National Academy of Sciences.

Rather than a uniform region of heat beneath, like a pancake griddle, geothermal sources under the Thwaites Glacier more resemble a stove top with a multitude of burners emitting heat in different locations and at different levels, research scientist Don Blankenship says.

“It’s the most complex thermal environment you might imagine,” he says. “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.”

The geothermal heat under the glacier averages around 100 milliwatts in each square meter, the researchers said, with some hotspots putting out 200 milliwatts per square meter.

Under the Earth’s other continents the average is less than 65 milliwatts per square meter, they said.

The Thwaites Glacer is an outflow glacier — pushing into the Amundsen Sea — that is the size of Florida and hold the key to trying to predict possible future rises in sea levels, they said.

Studying it could help yield clues to the future state of the entire West Antarctic Ice sheet, they added.

A complete collapse of Thwaites Glacier could push global sea levels up by three to six feet, and a melting of the entire ice sheet could double that, the researchers said.

The combination of warm ocean water and underlying geothermal heat makes the future of the glacier difficult to predict, lead study author Dusty Schroeder says.

“The combination of variable subglacial geothermal heat flow and the interacting subglacial water system could threaten the stability of Thwaites Glacier in ways that we never before imagined,” he says.

http://www.techtimes.com/articles/8268/20140610/underground-volcanoes-spur-antartic-glaciar-melt.htm

plants

Plants that were frozen during the “Little Ice Age” centuries ago have been observed sprouting new growth, scientists say. Samples of 400-year-old plants known as bryophytes have flourished under laboratory conditions. Researchers say this back-from-the-dead trick has implications for how ecosystems recover from the planet’s cyclic long periods of ice coverage. The findings appear in Proceedings of the National Academy of Sciences.

They come from a group from the University of Alberta, who were exploring an area around the Teardrop Glacier, high in the Canadian Arctic. The glaciers in the region have been receding at rates that have sharply accelerated since 2004, at about 3-4m per year. That is exposing land that has not seen light of day since the so-called Little Ice Age, a widespread climatic cooling that ran roughly from AD 1550 to AD 1850.

“We ended up walking along the edge of the glacier margin and we saw these huge populations coming out from underneath the glacier that seemed to have a greenish tint,” said Catherine La Farge, lead author of the study.

Bryophytes are different from the land plants that we know best, in that they do not have vascular tissue that helps pump fluids around different parts of the organism. They can survive being completely desiccated in long Arctic winters, returning to growth in warmer times, but Dr La Farge was surprised by an emergence of bryophytes that had been buried under ice for so long.

“When we looked at them in detail and brought them to the lab, I could see some of the stems actually had new growth of green lateral branches, and that said to me that these guys are regenerating in the field, and that blew my mind,” she told BBC News. “If you think of ice sheets covering the landscape, we’ve always thought that plants have to come in from refugia around the margins of an ice system, never considering land plants as coming out from underneath a glacier.”

But the retreating ice at Sverdrup Pass, where the Teardrop Glacier is located, is uncovering an array of life, including cyanobacteria and green terrestrial algae. Many of the species spotted there are entirely new to science.

“It’s a whole world of what’s coming out from underneath the glaciers that really needs to be studied,” Dr La Farge said.

“The glaciers are disappearing pretty fast – they’re going to expose all this terrestrial vegetation, and that’s going to have a big impact.”

http://www.bbc.co.uk/news/science-environment-22656239