Improved geoid solution for the Weddell Sea region

We present a geoid solution for the Weddell Sea and adjacent continental Antarctic regions. There, a refined geoid is of interest, especially for oceanographic and glaciological applications. For example, to investigate the Weddell Gyre as a part of the Antarctic Circumpolar Current and, thus, of the global ocean circulation, the mean dynamic topography (MDT) is needed. These days, the marine gravity field can be inferred with high and homogeneous resolution from altimetric height profiles of the mean sea surface. However, in areas permanently covered by sea ice as well as in coastal regions, satellite altimetry features deficiencies. Focussing on the Weddell Sea, these aspects are investigated in detail. In these areas, ground-based data that have not been used for geoid computation so far provide additional information in comparison with the existing high-resolution global gravity field models such as EGM2008. The geoid computation is based on the remove-compute-restore approach making use of least-squares collocation. The residual geoid with respect to a release 4 GOCE model adds up to two meters and more in the near-coastal and continental areas of the Weddell Sea region, also in comparison with EGM2008. Consequently, the thus refined geoid serves to compute new estimates of the regional MDT and geostrophic currents.

Die Gletscher der bolivianischen Anden, Verbreitung von Gletschern und neuzeitlichen Moränen in der Cordillera Apolobamba Cololo Region (Ostkordillere)

The uniform triangulation of the whole glacierized area of the Eastern Cordillera of Bolivia provided the first comparable geometrie basis for an accurate photogrammetric height evaluation of glaciers in the mountain range from the far south up to the Peruvian border. A total of 1775 glaciers, larger than 0.1 ha, were recorded in 16 mountain ranges ofthe East- ern Cordillera. Snow lines in the outer tropics can now be analysed with an accuracy of European standards. In spite of the widemeshed network of meteorological stations this allows a more pre- eise climatic differentiation to be made, particularly at high altitude sites. The methods and results of the analysis are described. Because of these results it becomes necessary to revise and refine previous concepts of the spatial distribution of climatic phenomena. Characteristics of glaciers in the Bolivian Cordillera obviously depend on the NE to SW decline in precipitation. The snow lines which are found at an altitude of 4500 m on the north- eastern slope directed towards the Yungas climb up to 5200 m on the lee slope towards the Alti- plano. The N to S increase in snowline elevation is not as significant as expected. With some res- ervation a 100 m fall in the snowline elevation in the Bolivian Cordillera can be explained by an increase in precipitation of about 50 mm.