Reconstructing Front system movement for the Southern Ocean during the mid-Pleistocene transition using palynology

Abstract

Reconstructing the front system movement during the mid-Pleistocene transition (MPT) will give understanding for the regional climate for the Southern Ocean (SO). The front movement will provide insight for the climatic conditions of the SO and the Antarctic continent during the MPT. The MD 218 Crotale expedition recovered multiple piston cores from the Del Caño Rise in 2019. These cores contained new climate data for the Pleistocene. Palynology was used to determine and count the dinoflagellate cysts present in the samples. The abundance percentage for each species was calculated and linked to a specific cluster determined by Thöle et al (2023). These clusters correspond to specific oceanographic conditions and allow for the reconstruction of the front movement trough time. This was done using a age model that was constructed based on a peak to peak comparison between the LR04 Benthic δ18O record, the L*color record and the δ18O stack of the MD19-3576 core. Samples form 860 to 740 ka were used and 6 different clusters were present in the core that determined the front movement of the SO front systems. During the glacials the fronts expended to the north, while the movement during the interglacials was to the south. The trend of the front movement generally followed the Marine Isotope Stages (MIS) determined by (Lisiecki & Raymo, 2005). The Del Caño Rise area was located close to the south side of the Polar Front (PF) for most of the MPT but the Subtropical Front and the Subantarctic Front have also been present at the Del Caño Rise area. On a more regional scale we find more variation showing that there is a difference between the regional and global climate for the SO. This difference helps us in understanding more about the intricacies of Antarctica and the Southern Ocean