Our patience for the beginning of our main research program has been really tried on this expedition, even though we were prepared for the long transit throughout the early stages of the expedition planning. After departing from the Ekström Ice Shelf of Neumayer Station, it took another 10 days until we finally arrived in the Bellingshausen Sea a few days ago. The transit across the Weddell Sea went without much delay, although we had to break through patches of dense and thick ice. On 15 January, we saw rocky land for the first time after leaving Cape Town. It was the northern tip of the Antarctic Peninsula that separates the Atlantic from the Pacific sector of Antarctica. This day offered also an opportunity for the traditional southern polar baptism – a lot of fun for all.
For several days, our meteorologists Jens and Christian had been observing the passage of low pressure areas with strong storms along the Bellingshausen Sea and the Antarctic Peninsula. After some consideration, the captain and the chief-scientist decided for the inner route between the mainland and the islands of the Antarctic Peninsula which is better protected from the storms. The first stage was easy to follow. The high number of cruise ships we encountered that far south of this island world was remarkable, but the – by now – ice-free summer seasons along the entire western Antarctic Peninsula make it possible. Excitement grew in the southern stage of the Peninsula. This inner route by passing Adelaide Island along its eastern coast was never taken before by Polarstern and has been used only by very few ships. Sea charts is quite inaccurate here. We followed a narrow path between shallows which was mapped by another ship – an exhausting job for the captain and nautical officers. It turned out that this route has important advantages: It takes about the same time as the open-sea route, and one is better protected from the storms of the Southeast Pacific. Future Polarstern expeditions may use this option. We passed by the British Rothera Station, during which we had a cheerful radio exchange with the station crew, then sailed into the open sea, and one day later we arrived in our main research area of the Bellingshausen Sea continental shelf.
Image Gallery
Some of the sea-floor mapping in the region of Ronne Entrance on the eastern Bellingshausen Sea shelf. The morphological structures on the sea floor were formed by earlier glacier movements. Johanna, Kolja and Simon of the bathymetry team are intensively discussing these formations (Photo: Karsten Gohl).
West Antarctica – about half the size of Europe – poses a serious problem for the next generations: Large amounts of its ice sheet melts and contribute to the global sea level rise. In particular its Pacific sectors at the Amundsen Sea and Bellingshausen Sea are affected by this loss of ice masses. What is so dramatic about the retreat of this region’s glaciers? Their subglacial base in the hinterland of West Antarctica lies down to two kilometres beneath sea level, meaning that their bed deepens toward the hinterland. This causes the incursion of relatively warm water masses from the South Pacific beneath the ice shelves and their grounding zones, where these water masses melt the ice from below. The collapse of a major part of the West Antarctic Ice Sheet would contribute about three to five meters to the sea level rise.
Although the processes of present melting are largely understood, it remains unclear how rapid and to where this ice sheet retreat will occur further on. Indications on the behaviour of the ice sheet and its glaciers during naturally occurring warm time periods of the geological past, such as the last interglacial period at about 120 thousand years ago or the warm period at three to four million years ago in the Pliocene, which is comparable to the present climate, can be very helpful. Finding out about exactly these past processes and their comparison to the present, human-made rapid climate change is the main goal of our expedition. We began our work with detailed sea floor mapping of the size of London, using the multi-beam echosounding system, to map the glaciomorphological bedforms that were formed during the last advance and retreat of the ice sheet. The marine geologists identified suitable locations on this map from which they sampled sediments using a gravity corer and grab sampler. This material contains microfossils and minerals that are used to determine the age and origin of the sediments that were transported from earlier glaciers – allowing the reconstruction of the ice sheet dynamics.
Daniela and Anne, both land geologists, were sitting in the helicopter to be flown to the very few rock outcrops in the coastal region that are not covered by ice to collect rock samples rocks. Later in their labs, they will perform geochemical analyses of certain rock minerals and their elements from which it is possible to estimate the time these rocks were uncovered from ice, thus estimating the ice sheet retreat. While the seismic team still has to wait, the two geophysicists Mareen and Caroline are busy with measuring the geothermal heat flow by ramming a so-called temperature-gradient probe into the sea floor. The value of this heat flow from the Earth’s interior is one of the parameters affecting the flow of glaciers and ice streams over their bed.
The weather is currently quite favourable for our work progress so that one looks into happy faces in all groups.
Best regards and wishes
Karsten Gohl
(Chief Scientist)
Further information on PS134:
Frequent short blogs: https://follow-polarstern.awi.de/
125-year anniversary of Belgica expedition: https://125yearsbelgica.com/