PolarGAP

The main focus of the PolarGAP project is to provide new high-resolution gravity data for global gravity and geoid models (the Geoid is a model of the Earth’s surface that represents the mean global sea level).

These global geodetic models have been revolutionised in terms of resolution and coverage by satellite gravity data. However, the satellite orbits do not track over the poles, leading to significant gaps and potential errors in the global models. Airborne gravity data provide the key bridging dataset completing these global models. Improved geodetic models are critical for a number of applications ranging from improved planning of satellite orbits, to better definition of surveying datum’s.

Primary aims

• Fill the Antarctic polar gap in GOCE satellite gravity coverage through collection of new airborne gravity data and combination with data from existing surveys in the South Pole region.
• Validation of differences in surface elevation observed by CryoSat-2 when traveling in opposite directions, by using airborne Lidar and the the innovative ASIRAS Radar System to measure the ice sheet surface and structure of the shallow snow pack.

Additional aims

• Exploring the geological structure and evolution of East and West Antarctica in the South Pole region with new magnetic and gravity data
• Investigating Antarctic ice sheet dynamics around South Pole using airborne radar to map the sub-ice mountains and valleys, distribution of subglacial water and internal ice sheet structures.

Science challenges

During the PolarGAP survey we will be exploring one of the key frontier regions in Antarctica using a range of geophysical techniques. East Antarctica is a geological composite, made up of a mosaic of tectonic fragments scarred by ancient sutures and cut by rifts.

This survey will allow linking between the sparse rock outcrops towards the coast and previous geophysical surveys in the continental interior. The data will provide unique new insights into sub-ice geology and the evolution of the crustal architecture of East Antarctica, laying the foundations for future research.

The study area we are targeting includes the catchments of several massive glaciers which link the vast East Antarctic Ice sheet to the potentially less stable West Antarctic ice sheet. Our new radar measurements of ice thickness, subglacial topography, basal water and ice sheet structure will better constrain both the processes operating beneath the ice sheet interior today, and the past and possible future evolution of the ice sheet. This is particularly critical close to the subglacial Recovery Lakes, which could be a store of water capable of lubricating down-stream ice flow.

Our final science target relates to the processes operating on the ice sheet surface. Satellite data shows an unusual pattern of cross-over errors in surface elevation depending on the direction the satellite is orbiting. This pattern is hypothesised to reflect unusual shallow snow fabric developed due to the consistent prevailing wind direction. By flying the ASIRAS radar, an analogue of the space-borne system, over these anomalies we will test this hypothesis. Additional data from a scanning LIDAR system will provide new information about the ice sheet surface, unattainable by satellite observations.