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article imageMega-canyon bigger than Grand Canyon found below Greenland's ice

By Robert Myles     Aug 31, 2013 in Science
Scientists have mapped a previously unknown canyon entombed below two kilometers of ice in Greenland. The discovery was made by a group of scientists from Bristol University’s School of Geographical Sciences in the UK.
The newly-found mega-canyon has been measured as being at least 750 kilometers (469 miles) long and 800 metres (2625 feet) deep in places. That places the Greenland canyon in the same league as the Grand Canyon, but at 750 kilometres long, the hidden Greenland canyon comfortably exceeds the length of its Arizona rival which runs for a mere 446 kilometers.
The Bristol scientists believe the previously unknown geographical feature predates the Greenland ice sheet by several million years and report the Greenland canyon as having the characteristics of a meandering river channel.
Lead author of the study, Professor Jonathan Bamber of Bristol University's School of Geographical Sciences, 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.”
In their research, scientists used thousands of kilometers of airborne radar data, collected mainly by NASA and researchers from the UK and Germany over several decades. From that they pieced together the landscape lying beneath the ice sheet that covers most of Greenland, obscuring it from view.
Ice is transparent to radio waves at certain frequencies and effectively, by using radar, scientists were able to bounce signals off the bedrock underlying the swaddling ice-sheet and assemble their data. By analysing all the radar data consistently, the University of Bristol team put together a ‘picture’ of a continuous bedrock canyon extending from almost the centre of the island of Greenland, terminating at its northern extremity in the deep fjord of the Petermann Glacier connecting to the Arctic Ocean.
The mega-canyon is thought to play an important role in transporting sub-glacial meltwater produced at the bed from the interior to the edge of the ice sheet and ultimately into the Arctic Ocean.
Four million years ago, at a time before the ice sheet obscured most of the Greenland landmass as we know it today, scientists say the evidence suggests the canyon provided a pathway for water from the interior to the coast. In other words, it was at one time a significant fluvial or river system.
The research was funded jointly by a European Union program, ‘ice2sea’ and the UK’s Natural Environment Research Council (NERC). Ice2sea, funded by the European Commission, brings together scientific and operational expertise from 24 leading institutions across Europe and beyond. It aims to improve understanding and gain more accurate projections of the contribution melting ice makes to rising sea-levels. In 2007, the fourth Intergovernmental Panel on Climate Change (IPCC) report highlighted ice-sheets as the most significant remaining uncertainty in projections of sea-level rise.
Professor David Vaughan, ice2sea co-ordinator at the British Antarctic Survey in Cambridge said: “A discovery of this nature shows that the Earth has not yet given up all its secrets. A 750 km canyon preserved under the ice for millions of years is a breathtaking find in itself, but this research is also important in furthering our understanding of Greenland’s past. This area’s ice sheet contributes to sea-level rise and this work can help us put current changes in context.”
A significant proportion of the new study utilised data collected from 2009 through 2012 by NASA’s Operation IceBridge, an ongoing six-year mission and the most comprehensive airborne survey ever of Earth’s polar ice caps. One of IceBridge's scientific instruments, the Multichannel Coherent Radar Depth Sounder, can penetrate deep into the ice-sheet, measuring its thickness and contours of the bedrock below.
Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., said, “Two things helped lead to this discovery. It was the enormous amount of data collected by IceBridge and the work of combining it with other datasets into a Greenland-wide compilation of all existing data that makes this feature appear in front of our eyes.
“It is quite remarkable that a 750km-long channel the size of parts of the Grand Canyon is discovered in the 21st century below the Greenland Ice Sheet. It shows how little we still know about the bedrock below large continental ice sheets.”
The full research paper, published yesterday, is available from the journal, Science, entitled, ‘Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet’ by Jonathan Bamber, Martin Siegert, Jennifer Griggs, Shawn Marshall and Giorgio Spada.
More about Greenland, icesheet, Rising sea levels, NASA Icebridge, glacial research
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