The western Weddell Sea is one of only a few regions of the southern Ocean covered by perennial sea ice. As such, it is of particular importance for atmosphere-ice-ocean processes and in particular for the oceanic freshwater balance. Therefore, the main objectives of the sea ice geophysical program were:

• Quantification of the regional variability of first- and second year sea ice and snow thickness in the north-western Weddell Sea, and observations of their interannual variability in comparison with earlier measurements of other researchers, obtained by drilling and upward-looking-sonar. In particular, we aimed at continuing observations performed during ISPOL (Ant XXII/2) in December 2005.

• Validation of satellite measurements of radar backscatter and surface temperature of different ice types and polynya processes by means of coincident real-time Envisat-SAR and NOAA-AVHRR imagery received on board, and in-situ measurements of ice and snow thickness and other physical properties. With an improved understanding of satellite signatures, the results of our in-situ measurements can be spatially extrapolated and extended to longer time periods.

• Investigation of physical and biological ice properties and processes and the fate of perennial ice after surviving one summer melt season. From earlier Polarstern cruises including ISPOL it is clear that the ice undergoes significant changes during the summer season. ANT XXIII/7 offered the opportunity to study the fate of this ice during the following winter, in particular the properties of remnant metamorphous snow, superimposed ice, and refrozen gap layers.

We performed one cruise:

• WWOS 2006