Our research time on the Bellingshausen Sea rapidly diminishes day by day. Only one week remains which we use to work entirely in the Eltanin Bay, located in the southernmost part of the Bellingshausen Sea continental shelf. Here, various ice streams flow into the few remaining ice shelves or directly into the ocean. In this letter we present the work of the geothermal heat flow team and that of the jellyfish group.
Parallel to the sediment coring stations of the marine geology group, Mareen and Caroline have been busy measuring the temperature of the sediments below the seafloor at various locations on the inner continental shelf. A lance of 5 m length onto which highly sensitive temperature sensors are connected (Figs. 1 and 2) is lowered to the seafloor and pushed into the sediments by its own weight. Similar to a thermometer, the sensors measure the temperatures of the surrounding sediment. The differences at various depths depict the prevailing geothermal heat flow. The magnitude of the geothermal heat flow is influenced by the geological setting and tectonic activity. Hence, high heat flow could indicate regions of tectonic rifting, such as supposedly in Eltanin Bay, where warm material from the Earth’s mantle was transported towards the surface. The geothermal heat flow plays a key role in the basal ice-sheet sliding and melting processes. Relatively warm areas of the Earth’s crustal surface of the present continental shelf could have had a significant influence on a rapid ice mass loss of past ice sheets covering this shelf in the Bellingshausen Sea. In order to improve predictions of potential global sea level changes, it is crucial to better understand such past and present basal ice-sheet sliding and melting processes.
Gerlien, Micaela and Joan of the “Southern Ocean Jellyfish” (SO-JELLY) team worked already along our transect from Cape Town to Neumayer Station in the Southern Atlantic. They have resumed their sampling work in the Bellingshausen Sea of the Antarctic Southern Pacific. Gelatinous zooplankton comprise jellyfish, comb jellies, and salps. Despite their importance in marine pelagic ecosystems being increasingly recognized, they are largely understudied in the Southern Ocean, even more so in the Bellingshausen Sea. By combining deployments of plankton nets to collect specimens and sampling water with a bottle sampling device at different water-depths for environmental DNA (so-called environmental or e-DNA), the group aims to get a full image on the jellies’ diversity, distribution, ecology, trophic role, and genetic connectivity. So far, they have collected over 1300 jellyfish samples ranging from a few millimetres to a few centimetres in size and filtrated over 700 liters of sea water from different locations and depths to collect such eDNA samples. This baseline knowledge will help predicting the effects of climate change on the ecosystem, and what the future Antarctic pelagic composition and food webs will look like.
We cannot repeat it often enough, but the support of the ship’s crew for our research work is simply phenomenal.
Best regards and wishes,
Mareen Lösing, Gerlien Verhaegen and Karsten Gohl
Further information on PS134:
Frequent short blogs: https://follow-polarstern.awi.de/
125-year anniversary of Belgica expedition: https://125yearsbelgica.com/