Category: Glaciers


ICE WORLD

Preglacial landscape found deep under Greenland ice


by Staff Writers
Washington (AFP) April 18, 2014

US geologists said Thursday they have uncovered a preglacial tundra landscape preserved for 2.7 million years far below the Greenland ice sheet.

Glaciers are known to scrape everything off any given plot of land — vegetation, soil and even the top layer of bedrock — so scientists expressed great surprise that they had found the landscape in pristine condition below two miles (three kilometers) of ice.

The finding provides strong evidence that the ice sheet has existed for much longer than previously known, and survived numerous global warming episodes, according to the lead researcher, University of Vermont geologist Paul Bierman.

Rather than scraping and sculpting the landscape, the ice sheet has been frozen to the ground, effectively creating “a refrigerator that’s preserved this antique landscape,” Bierman said.

The finding suggests that even during the warmest periods of the ice sheet’s life, the center of Greenland was stable and did not fully melt, allowing the tundra landscape to be sealed without modification through millions of years of changing temperatures.

 

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Massive canyon discovered buried under Greenland ice

A vast gorge in the Earth on the same scale as the Grand Canyon lies buried under ice in Greenland, scientists have learned.

The massive hidden canyon is at least 466 miles (740km) long and up to 800 metres (2,600ft) deep in places.

The feature, resembling a meandering river channel, is believed to pre-date the ice sheet that has covered Greenland for millions of years.

3D visualisation of the canyon under Greenland's ice sheet.

3D visualisation of the canyon under Greenland’s ice sheet. Photograph: Professor Jonathan Bamber

Prof Jonathan Bamber, from the school of geographical studies at the University of Bristol, said: “With Google Streetview available for many cities around the world and digital maps for everything from population density to happiness, one might assume that the landscape of the Earth has been fully explored and mapped.

“Our research shows there’s still a lot left to discover.”

The canyon was uncovered by airborne radar which can penetrate ice and bounce off the land beneath.

Scientists pieced together radar measurements covering thousands of kilometres collected by Arctic researchers over several decades. They found evidence of a fissure in the bedrock stretching northwards almost from the centre of Greenland.

The canyon ends in a deep fjord connecting it to the Arctic ocean.

 

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Greenland glacier hits record speed

Ilulissat Icefjord Jakobshavn is located at the eastern end of the Ilulissat Icefjord (seen here), Greenland

In summer, the Jakobshavn Glacier – widely thought to have spawned the iceberg that sank the Titanic – is moving about four times faster than it was in the 1990s.

The Greenland Ice Sheet has seen record melting in recent years and would raise sea levels 6m were it all to vanish.

Details of the research are published in The Cryosphere journal.

Ian Joughin and Ben Smith of the University of Washington’s Polar Science Center in Seattle analysed pictures from the German TerraSAR-X satellites to measure the speed of the glacier.

“As the glacier moves we can track changes between images to produce maps of the ice flow velocity,” said Dr Joughin, the study’s lead author.

In the summer of 2012, the glacier reached a record speed of more than 17km per year – more than 46m per day.

“We are now seeing summer speeds more than four times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland,” Ian Joughin explained.

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National Geographic

A photo of the Jakobshavn Glacier.

Chunks of ice litter the ocean in front of Greenland’s Jakobshavn glacier.

PHOTOGRAPH BY PAUL SOUDERS

Jane J. Lee

National Geographic

Published February 4, 2014

A Greenland glacier named Jakobshavn Isbrae, which many believe spawned the iceberg that sank the Titanic, has hit record speeds in its race to the ocean. Some may be tempted to call it the king of the glacier world, but this speedy river of ice is nothing to crow about.

A new study published February 3 in the journal Cryosphere finds that Jakobshavn’s averaged annual speed in 2012 and 2013 was nearly three times its rate in the 1990s. Its flow rate during the summer months was even faster.

“We are now seeing summer speeds more than four times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glaciers in Greenland,” Ian Joughin, a researcher at the University of Washington in Seattle, told the BBC.

In summer 2012, Jakobshavn reached speeds of about 150 feet (46 meters) per day.

Other glaciers may periodically flow faster than Jakobshavn, but Greenland’s most well known glacier is the bellwether of climate change in the region and likely contributes more to sea-level rise than any other glacier in the Northern Hemisphere—as much as 4 percent of the global total, Joughin and his colleagues found in an earlier study. (Read about glacial meltdown in National Geographic magazine.)

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Climate change is taking a visible toll on Yosemite National Park, where the largest ice mass in the park is in a death spiral, geologists say.

During an annual trek to the glacier deep in Yosemite’s backcountry last month, Greg Stock, the park’s first full-time geologist, found that Lyell Glacier had shrunk visibly since his visit last year, continuing a trend that began more than a century ago.

Lyell has dropped 62% of its mass and lost 120 vertical feet of ice over the last 100 years. “We give it 20 years or so of existence — then it’ll vanish, leaving behind rocky debris,” Stock said.

The Sierra Nevada Mountains have roughly 100 remaining glaciers, two of them in Yosemite. The shrinkage of glaciers across the Sierra is also occurring around the world. Great ice sheets are dwindling, prompting concerns about what happens next to surrounding ecological systems after perennial rivulets of melted ice disappear.

“We’ve looked at glaciers in California, Colorado, Wyoming, Washington and elsewhere, and they’re all thinning because of warming temperatures and less precipitation,” said Andrew Fountain, professor of geology and geography at Portland State University in Oregon. “This is the beginning of the end of these things.”

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