Carbon Exchange and Ocean Ventilation along the East Antarctic Margin

The Southern Ocean (SO) plays a crucial role in regulating the Earth’s climate by absorbing atmospheric carbon and storing it in the deep ocean. (Brovkin et al., 2012). Past studies reported a reduction in this uptake capacity over the last few decades. However, the temporal and spatial variability of the Southern Ocean’s carbon pump appears to be more complex  (Landschützer et al., 2015), with the Indian sector arguably being the least explored and understood region. A key objective of this PhD is to use radiocarbon signatures of dissolved inorganic carbon (DI¹⁴C), combined with stable carbon isotopes to quantify exchange processes between the ocean, atmosphere and sediments along the East Antarctic margin. A comprehensive sample set of sea water, sediment pore water and sediment surface samples was collected during three expeditions (2022 - 2024) on R/V Polarstern from more than 50 stations. Several sites from key locations will be selected to study ocean ventilation, water mass alterations and exchanges, and bottom water formation in the region. In addition, we will perform analyses in high spatial resolution to target more specific research questions, in particular ocean – ice shelf interactions. The East Antarctic coast from Prydz Bay to Vincennes Bay lends itself as case study area for tracing the inflow of Circumpolar Deep Water onto the continental shelf and its interaction with the marine-based portions of the Amery and Shackleton Ice Shelves, as well as Totten Glacier. Sections sampled along meridional transects further offshore and to the west allow to differentiate between regional varieties of Antarctic Bottom Water formation. Comparing water column data with ¹⁴C signals recorded in surface sediment benthic foraminifera will contribute to an improved understanding of the use of radiocarbon as a ventilation age proxy. Initial analyses are being conducted at the radiocarbon laboratory at Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, equipped with an accelerator mass spectrometer (AMS) Mini Carbon Dating System (MICADAS). Next steps involve method development, focusing on optimizing the graphitization process of DIC samples prior to radiocarbon analysis.

Brovkin, V., Ganopolski, A., Archer, D., & Munhoven, G. (2012). Glacial CO 2 cycle as a succession of key physical and biogeochemical processes. Climate of the Past, 8(1), 251-264.

Landschützer, P., Gruber, N., Haumann, F. A., Rödenbeck, C., Bakker, D. C., Van Heuven, S., ... & Wanninkhof, R. (2015). The reinvigoration of the Southern Ocean carbon sink. Science, 349(6253), 1221-1224.