Reconstructing oceanographic changes and the evolution of the "cold water route" through glacial-interglacial variability of MIS 12-11 in the Falkland Region, Southern Atlantic Ocean

Abstract

The nature of palaeoceanographic changes has been reconstructed at the Falkland region (Atlantic sector of the Southern Ocean) during the glacial-interglacial transition of MIS 12-11 (~400,000 years ago). Organic proxies for the reconstruction of surface oceanographic conditions were used, notably organic-walled dinoflagellate cyst paleo-assemblages and biomarker proxy TEX86 for sea surface temperature reconstruction. This proxy-combination was applied on the sedimentary Core U1534 (IODP Expedition 382). The dinoflagellate cysts reflect a notable change from a S. antarctica- to N. labyrinthus-dominated assemblage, indicating a clear transition from glacial to interglacial conditions but with relative cold and dynamic waters related to the Subantarctic Front. However, the TEX86-based sea surface temperature reconstruction displays a mirrored trend to the general warming pattern of MIS 11, with a cooling trend (from ~13°C to 6-8°C) during the transition into MIS 11 and stable cool temperatures throughout most of the interglacial, but a sharp rise at the later stage of MIS 11 (ca. 30,000 years after the termination). A potential explanation is suggested by the enhanced transport of cold water via the Subantarctic Front into the Southwest Atlantic Ocean (commonly referred to as the cold water route). This appeared to subdue interglacial warming in the Falkland Region, until the cold water route weakened during the later stage of MIS 11, allowing a delayed warming of sea surface water in the region. The study helped to understand changes in the position and strength of the Antarctic Circumpolar Current and provided an insight into the connectivity of cold, pacific-sourced subantarctic water via the Subantarctic Front into the Southern Atlantic Ocean during and towards a previous warm climate interval.