In this last expedition letter of PS145, Klaus Lucke begins with a description of the work of the whale research group and their research project, which is linked to the seismic and hydroacoustic surveys of our expedition. I will then draw a summary and conclusion of this expedition.
The whale research team consists of three marine biologists, one veterinarian and two drone experts, who aim to learn more about the distribution and behavior of marine mammals in this Antarctic region and to validate the mitigation measures employed on board of Polarstern during operation of hydroacoustic methods in the Bellingshausen Sea. Such mitigation measures are required as the sound emitted by hydroacoustic surveys, performed by the multibeam echosounder, the sediment-echosounder and the seismic source, has the potential to affect the animals in various ways. Our main method to prevent this risk is the observation by professional marine mammal observers assisted by a group of trained observers, who monitor the area surrounding Polarstern for any occurrence of marine mammals. In total, about 400 whales and countless seals have been sighted with most of them identified according to their species. Several times the hydroacoustic sources had to be shut down when animals entered the safety zone around the ship. The whale research team used a drone equipped with a high-resolution video system (Fig. 1) and an underwater sound recorder to detect as many animals as possible visually and acoustically near and far from Polarstern. Unfortunately, the drone was severely damaged during a test flight in the beginning of the expedition, but with his talented skill and the support of the ship’s engine and deck workshops John was able to repair the drone, so that observation flights could be performed after all. As an additional opportunistic platform for studying marine mammal distribution over a larger range from the vessel, the team joined helicopter flights which were conducted for ice reconnaissance.
Monday was the last day of our research activities of this expedition, and the geologists Daniela and Anne tried to collect rock samples from volcanic Peter I Island. However, the selected outcrop area did not offer any suitable landing spots for the helicopter so that they had to give up. During the previous days, we worked on the westernmost shelf of the Bellingshausen Sea near the Abbot Ice Shelf, which is an area that had not been visited by ships before. The lack of sea-ice in this season made it possible that we were able to survey and take sediment samples from newly discovered glacial troughs along which former ice streams had flown. Also, the biologists were happy to collect jellyfish and other pelagic species for the first time in this region.
Currently, we are on our 6-day-long transit across the southeastern Pacific to Punta Arenas. We have spent almost 10 weeks on this ship with its fantastic crew and collected huge amounts of geophysical, geological and biological data and samples from a region that was previously difficult to access. The record sea-ice minimum in this Antarctic summer season made it possible to sail almost everywhere on the continental shelf of the Bellingshausen Sea to pursue our research objectives. More than 3700 km of seismic profiles of excellent data quality, densely spaced surveys of the seafloor in various areas with a total size of several large cities, 29 sediment coring stations with very good cored material, 20 measurement locations for geothermal heat flow, collection of rocks from 10 location on sparsely distributed outcrops on land and small islands, 16 sampling locations for jellyfish, and numerous observations of whales (Fig. 2) and seals make up the achievement of this expedition. The amount and quality of the data and samples raise the expectations for important new knowledge about the ice-sheet history and processes, as well as an improved understanding of the ecological system in the Bellingshausen Sea sector. A first glimpse of very dynamic former glacier and ice stream motions in this region can already be seen in the gridded maps of our new multibeam echosounding data of the seafloor (Fig. 3). All scientists will be busy to analyze and evaluate the data and samples in the labs of the AWI and cooperation partners in the next months and years for various publications.
In addition to the responsibility for the research program, as an expedition leader one is always concerned about the well-being of the participants and a good life and work atmosphere on board during such long expeditions on which, naturally, not everything goes according to plan. However, this wonderful scientific participant team of 49 persons from 13 nations has worked together in such a friendly and supporting spirit with mutual support for the successful deployment of equipment and in sampling work as well as in the daily life on board. For this I am very grateful.
Two support teams have also contributed to the success: The meteorologists Jens Kieser and Christian Rohleder of the German Weather Service (DWD) have predicted the daily weather with such an incredible accuracy that we were able to optimize our planning of equipment deployment from the ship and the helicopter operations. Our excellent helicopter crew with the pilots Lars Vaupel and Jens Brauer of NHC Northern Helicopter and their mechanics Gabriel Panter and Michael Seifert of DRF Luftrettung made every flight request for ice reconnaissance and science activities possible as long weather conditions did not place restrictions.
The most grateful thanks go to the unique and outstanding ship crew of Polarstern under leadership of Captain Moritz Langhinrichs. They wonderfully supported us with navigational route planning, with our deployment of various equipment from the deck, with assistance from the engine and deck workshops, and with their friendly kitchen and mess room service team. Dear crew, you are a dream team!
We are now looking forward to the impressive highlight of natural surroundings when we will pass through the western Strait of Magellan between Patagonia and Tierra del Fuego just before our arrival in Punta Arenas (Chile) on 6 March.
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/