VISA is a mutual scientific project of TU Dresden and AWI Bremerhaven, funded by the German Research Foundation.

Scientific goals:

The polar regions and especially Antarctica with its ice sheet play a key role in the complex system “Earth”. The interactions of the Antarctic ice sheet with the atmosphere, the world ocean and the solid earth significantly influence global processes like climate and changes of the global sea level. Therefore, the detailed knowledge of recent changes of the Antarctic ice sheet is of crucial, interdisciplinary importance. All changes of the ice sheet have also to be regarded as mass changes, which yield temporal changes of the gravity field of the Earth. Hereby, mass transfers between the ice and the ocean as well as mass changes of the solid Earth due to load changes are included.

Such temporal variations of the Earth’s gravity field should be determined by new satellite missions with a life time of up to five years. Hereby, one awaits also detailed statements on the status of the Antarctic ice sheet. The gravity field missions CHAMP (launched July 15, 2000), GRACE (launched March 17, 2002) and GOCE are capable to measure only an integrated gravity signal, which is also influenced by factors other than the mass balance of the ice sheet. Those factors are for example: changes in the lithosphere caused by postglacial rebound and tectonic processes as well as long-term changes in the atmospheric pressure variation. It is necessary to record and to quantify all gravimetric signals in order to determine mass-induced effects and thus to minimize errors while calculating the mass balance of the ice sheet. Therefore, the results of the CHAMP, GRACE and GOCE missions should be validated by repeated airborne and terrestrial observations. Only such additional and densifying measurements in Antarctica will allow to make scientifically proved statements on the topical mass balance of the Antarctic ice sheet.

Planned Work:

The region Schirmacher Oasis – Potsdam Glacier – Wohlthat Massif was the first test area in the season 2003/04 (see figure 1). During the VISA campaign 2004/05 fieldwork were done in the region Kottas camp / Heimefrontfjella (see figure 2). Besides the airborne measurements the following terrestrial observations were planned to be carried out, which will be used for the detailed investigation of height changes, gravity changes and mass changes (and especially of the ablation/accumulation pattern; in the test area Kottas, cf. Figure):

• Geodetic measurements (static and kinematic GPS, precise gravimetry)
• Glaciological measurements (shallow firn cores, snow pits)
• Geophysical measurements (EMR)

In order to investigate the dynamics of the lithosphere, the following techniques should be applied (locations A to E, cf. Figure):

• Geodetic measurements (GPS and gravimetry on bedrock: height and gravity changes)
• Geophysical measurements (seismology: estimation of the seismicity and focal mechanisms)

Figures: