Airborne geophysical survey of the GOCE polar gap in Antarctica
20/09/2016 | 14:00 | Session 2: New measurement techniques
Author(s): Rene Forsberg, Arne Olesen, Tom Jordan, Fausto Ferracioli and Kenichi Matsuoka
Rene Forsberg, Arne Olesen, Tom Jordan, Fausto Ferracioli and Kenichi Matsuoka
GOCE has mapped the global gravity field with hitherto unprecedented accuracy and resolution, except for the polar gaps north and south of latitude 83.3 degree. While the Arctic gap has been filled since long with data of the Arctic Gravity Project, the Antarctic polar gap has been a major challenge. Completing the gravity field coverage of Antarctica has global significance for earth geopotential models (e.g., EGM2020), geoid determination and satellite orbits; completing the coverage if the Antarctic GOCE gap, in order to obtain a truly global gravity field coverage of the planet, has therefore been an obvious, but challenging, task for precise geodetic aerogravity surveys.
Such surveys have now been carried out in a major airborne geophysics campaign – the 2015/16 “Polar Gap” project. The ESA-sponsored Polar Gap project used a Twin-Otter aircraft equipped with several gravity sensors (spring gravimeter and IMU sensors), magnetometers, ice penetrating radar, and scanning lidar to collect a complete suite of airborne remote sensing data over essentially unmapped regions of the polar gap, along with more detailed flights over the subglacial Recovery Lakes region, to follow up earlier 2013 flights over this region.
The operations took place from two deep interior field camps, as well as from the Amundsen-Scott South Pole station, thanks to a special arrangement with NSF. In addition to the airborne gravity and geophysics program, data with an ESA Ku-band radar were also acquired, to investigate anomalous elevation change patterns seen by the CryoSat mission. In the talk we outline the Antarctic field operations, and show first results of the campaign, including performance of the gravity sensors, the gravity reference network, and the comparison to the limited existing gravity data in the region. We also show first results of computed gravity field gradients at altitude, to be used for enhancing current GOCE models. Examples of other acquired geophysical and lidar data are also given. Newly discovered major features discovered include a major subglacial valley system close to the South Pole, with ice thickness in excess of 4 km, as well as extended mountain systems under the ice, both consistent with observed ice stream patterns in the region.