Summary and itinerary

Since the last glacial maximum, the West Antarctic Ice-Sheet (WAIS) has experienced dramatic volume changes within short periods of time. The WAIS has the potential to increase the global sea-level by 3 to 5 meters. Hence, studies are urgently required to show if these short-term variations can be compared to volume changes in the older and younger geological past which will provide parameters for prediction models. With this high-priority objective in mind, we will begin the cruise leg ANT-XXVI/III of RV Polarstern in Wellington (New Zealand) on 30 January 2010. The expedition has primarily geophysical and geological objectives with the goal to decipher the pre-glacial and glacial development of West Antarctica. An oceanographic and a biogeochemistry program are also planned, and a marine mammal surveillance project will be conducted during the entire cruise.

The research program will begin with a geophysical and geological pre-site survey on proposed sites for an IODP drill proposal on the transit from Wellington to the eastern Ross Sea. From the eastern Ross Sea and along the continental margin off Marie Byrd Land, geophysical profiling will connect the existing data grid of the Ross Sea to the profiles in the Amundsen Sea and Bellingshausen Sea. Filling this large data gap is an important prerequisite for the reconstruction of a circum-Antarctic paleobathymetry for paleoclimate simulations. Arriving in the main working area of the Amundsen Sea Embayment, geophysical profiling and bathymetric surveying will continue to reveal the characteristics of sediments and basement with the aim to reconstruct the glacial-interglacial cyclicity from earliest glaciation to the last glacial maximum. The Pine Island Bay area is known for the recently accelerated retreat of the Pine Island and Thwaites Glaciers. Geothermal heat-flow measurements are expected to provide an insight into recent volcanic activities which may have an influence on ice-sheet dynamics. Cores of sediments will be collected for dating past ice-shelf retreats. Recently discovered cold-water corals will be sampled from the Marie Byrd Seamounts. Geological sampling projects at outcropping rock sites along the Marie Byrd Land coast are aimed to revealing the timing of the latest glacial retreat via cosmogenic nuclide analysis and to reconstruct the erosional and uplift history of Marie Byrd Land via fission-track analysis. Repeated and new GPS measurements on rock outcrops as well as on ice-shelves will be used to derive horizontal and vertical crustal motion and the motion and tidal behaviour of the ice-shelves. Oceanographic processes have been debated as likely causes for accelerated ice-sheet variations in West Antarctica. An oceanographic program with CTD casts in the Amundsen Sea Embayment is aimed to study the distribution and impact of Circumpolar Deep Water on the continental shelf and at the glacier mouths. Methane production during the phytoplankton bloom is a process not well understood in the Southern Ocean. Water samples will be collected for methane gas analyses. The dissolved gases will be analysed on board. Samples of Antarctic phytoplankton will be used to study their climate induced changes and biodiversity. Furthermore, a marine mammal surveillance will be performed during this expedition, using a thermal imaging device.

The expedition will end in Punta Arenas (Chile) on 5 April 2010.