Paleoceanographic changes in the Drake Passage over the past 600 kyrs

Abstract

Oceanographic conditions in the Southern Ocean are closely associated with the oceanic frontal system. Glacial-interglacial changes in cryosphere influence variations in oceanic fronts in the Southern Ocean and vice versa, causing oceanographic changes from surface to bottom including surface water productivity, nutrient utilization, bottom water chemistry, and bottom current intensity and changes in sediment provenance and sediment transport mechanisms. Here, we documented various multi-proxy records over the past 600 kyrs from the Drake Passage with previously published data to compare between glacial and interglacial oceanic conditions from surface to bottom. Biogenic opal (diatom) and export productions were high during interglacial periods and low during glacial periods. Surface water production was dominated by open ocean diatom species during both glacial and interglacial periods without a clear glacial-interglacial change in sea ice species. From Marine Isotope Stage (MIS) 9, interglacial biogenic opal and diatom abundance increased with decreased terrestrial influence. Nutrient utilization increased (decreased) during interglacial (glacial) periods with increased (decreased) surface water production, particularly after MIS 9. This indicates that surface water production was regulated by light availability in association with mixed layer depth. Sortable silt mean grain size increased (decreased) bottom current during glacial (interglacial) periods. Increased glacial bottom current is likely associated with southwestward flowing bottom current. Interglacial bottom current intensity became significantly weakened after MIS 9. Distinct interglacial warmth in the Drake Passage occurred from MIS 9, not following the global trend to occur after MIS 11. This implies that more studies from the Southern Ocean in response to the MBE are required in the future.