Newly discovered subglacial Antarctic mountains and valleys could impact sea level rise
The South Pole may seem like a flat desert of ice, but a recent international survey has discovered that there's a complex topography under the surface that could have a major effect on the Earth's sea levels. Using data collected by an extensive aerogeographic survey conducted as part of ESA's PolarGAP project, the new subglacial map of the Antarctic high latitudes reveals mountain ranges buried beneath the ice and three gigantic valleys that could control how the southern ice cap flows into the sea.
Modern satellites have revolutionized geo-surveying by not only allowing researchers to take images from hundreds of miles up using wide-spectrum cameras and radar, but by also probing the interior of the Earth using gravitational mapping. But according to the British Antarctic Survey (BAS), the South Pole is an area that gets overlooked. This is because the inclinations of most survey satellites are too low to pass over the poles, so data in general and gravity surveys in particular are a bit thin on the ground.
To make up for this, PolarGAP equipped de Havilland Canada Twin Otter aircraft with airborne, ice-penetrating radar to map the world beneath the ice south of latitude 83.5° and learn more about how the ice flows between the East and West Antarctic ice sheets.
BAS says that one of the most important subglacial features in the South Polar region is the presence of three huge valleys. These range in size from the Offset Rift Basin that is 150 km (93 mi) long and 30 km (19 mi) wide, to the Patuxent Trough that is over 300 km (186 mi) long and over 15 km (9 mi) wide, up to the Foundation Trough at more than 350 km (217 mi) long and 35 km (22 mi) wide. That makes the latter the equivalent length of the distance from London to Manchester and half again as wide as the length of Manhattan Island.
These chasms are of interest because, with the mountain ranges damming the ice in one direction, they help the ice to flow from the pole to the sea. According to the team, it's feared that if the ice cap should thin markedly in the future, then the speed of this flow could dramatically increase. If that happens, then more fresh water will end up in the surrounding ocean and sea levels around the world will rise faster. However, the new survey data should help to better model and predict this flow.
"Remarkably the South Pole region is one of the least understood frontiers in the whole of Antarctica," says Dr Fausto Ferraccioli, Head of Airborne Geophysics at British Antarctic Survey and the Principal Investigator of the PolarGAP. "By mapping these deep troughs and mountain ranges we have therefore added a key piece of the puzzle to help understand how the East Antarctic Ice Sheet may have responded to past change and how it may do so in the future. Our new aerogeophysical data will also enable new research into the geological processes that created the mountains and basins before the Antarctic ice sheet itself was born."
The research was published in Geophysical Research Letters.
Source: British Antarctic Survey
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The not floating ice must be *above sea level*. Any part of grounded ice that's below sea level would *lower* sea level slightly upon melting.
So cut a virtual partial sphere across Antarctica at sea level. All the ice below that level is of null import to sea level, other than the small negative effect it would have on sea level if it melted. It could be calculated how much above sea level to raise the cut surface to have the non-floating ice beneath be neutral, just like floating ice.
The ice above that level is only of interest to sea level impact if the ice below it is in contact with the ground beneath.