Time to map the uncharted Antarctica

Tuesday 22 Dec 15


René Forsberg
DTU Space
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Two researchers from DTU Space are to collect data about Antarctica to reveal the uncharted landscape beneath the ice, and to help ensure accurate satellite trajectories at the same time.

The likelihood of a white Christmas this year is 100 per cent. Or at least it is for Arne Vestergaard Olesen, Senior Researcher at DTU Space, who will be travelling to Antarctica in early December to apply his expertise in the area of gravity and magnetic field measurements to charting the last blank spot on the world map: the uncharted landscape under the ice cap at the South Pole. In January 2016, he will be relieved by his colleague, Professor René Forsberg, Head of Geodynamics at DTU Space, who will continue collecting data for the next four weeks before concluding the mission.

“We know nothing at all about the landscape under the ice in the central part of Antarctica. The region is around the same size as central Western Europe, and it may contain mountains, valleys, and huge pools ... no-one knows,” says René Forsberg, pouring out a constant stream of words as if to remind you that time is precious, and that there is much to do before the researchers can start packing their Parkas and sturdy boots that can withstand temperatures down to -40°C.

It is no coincidence that researchers from DTU’s Division of Geodynamics have been awarded the prestigious assignment in partnership with colleagues from Britain and Norway as a part of the international PolarGap assignment devoted to measuring the gravity and magnetic fields in the central areas of Antarctica south of 83°S.

They were chosen because DTU Space has extensive experience with mapping the Earth—often under extreme conditions and in the most inaccessible areas, including the North Pole and Greenland. They know that they need to carry their laptops next to their stomachs to keep them warm enough to operate, and that they need to handle the cables with care because they can become as brittle as uncooked spaghetti when the temperature drops below -30°C.

Photo: private 

The mission’s three objectives
The first time René Forsberg and Arne Vestergaard Olesen travelled to Antarctica on a mapping mission was in 2010, at the request of the United States.

“In 2009, we received a call from the American military mapping institution, which had heard about our work at the North Pole and on Greenland. They were impressed that we know how to keep our equipment running so efficiently at temperatures as low as -40°C, so they invited us to take part in the mapping of Antarctica, where you also have to combat the effects of the cold on the instruments,” relates René Forsberg.

The mission to Antarctica has three scientific objectives: To find out more about the landscape beneath the ice, and to build up comprehensive knowledge about the continent’s gravity. This will be achieved by flying carefully planned routes across Antarctica and using radar to collect data about the local magnetic and gravity fields.

The third objective is to test new instruments and use the experience gathered to develop them, as well as to secure data for calibrating the ESA’s polar CryoSat mission, which has trouble measuring changes in the ice in a zone around the South Pole itself.

Photo: private 

Accurate satellite trajectories
The gravity data from Antarctica are to be used in global reference models of the planet’s gravity field to ensure better determination of heights using GPS, to improve the measurement of sea currents, and to boost understanding of the inner structure of the Earth. The data will form part of a global partnership devoted to charting the gravity field, where the central area of Antarctica is the final ‘blank spot’ on the map for this type of data.

“Gravity varies from place to place, depending on the composition of the subterranean layers. It is essential to have an accurate image of the Earth’s gravity field in order to be able to generate accurate satellite trajectories. In places where gravitational pull is a little weaker, satellites tend to perform a small ‘jump’. This means that we don’t know the precise position of the satellite, which naturally affects the measurements it’s taking. Even a tiny jump of a few centimetres can be unfortunate, if the satellite is measuring sea levels, for example,” explains René Forsberg.

When the mission draws to a close in February 2016, the researchers will spend a year on calculations designed to improve the global gravity field models. The radar and gravity measurements collected during the mission are to be used to interpret the landscape beneath the ice. They may also provide important information about whether and how Antarctica is melting.

“If there are large lakes and valleys below the ice, it may melt faster than we expect. Because if the sea level rises, sea water can force its way in under the ice through the valleys and lakes and boost the melting process from below. Serious melting is significant for Denmark as well, because it is in the Northern Hemisphere that the sea level will rise if Antarctical melts,” concludes René Forsberg.

Facts about PolarGap

The mission: The international PolarGap project is devoted to measuring the gravity and magnetic fields south of 83S. The recently completed European Space Agency GOCE satellite mission was unable to cover this area on account of limitations in the satellite trajectory.

Partners: The measurements are being performed by DTU Space, the British Antarctic Survey and the Norwegian Polar Institute. Logistics are being handled by the National Science Foundation (USARP) and commercial logistics companies.

Funding: The European Space Agency (ESA) is the principal sponsor of the PolarGap project.

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