High resolution reconstruction of Southwest Atlantic sea-ice and its role in the carbon cycle during marine isotope stages 3 and 2

摘要: [1] Recent modeling suggests that changes in Southern Ocean sea-ice extent potentially regulated the exchange of CO2release between ocean and atmosphere during glacials. Unfortunately, a lack high-resolution records from has prevented detailed testing these model-based hypotheses with field data. Here we present sea-ice, for period 35–15 cal ka BP, derived diatom assemblages measured three glacial sediment cores forming an ∼8° transect across Scotia Sea, southwest Atlantic. Chronological control was achieved through novel combination abundance stratigraphy, relative geomagnetic paleointensity data, down-core magnetic susceptibility ice core dust correlation. Results showed winter edge reached its maximum northward ∼53°S, at least 3° north modern limit, ∼25 ∼23.5 predating Last Glacial Maximum (LGM). expansion summer also pre-dated LGM, advancing to 61°S, possibly as far 55°S ∼31 ∼12° advance position. A clear shift seasonal zone is evident following retreat related austral insolation forcing. This resulted expanded ∼22.5 BP deglaciation. Our data confirm had physical potential influence carbon cycle both barrier more importantly suppression vertical mixing cycling pre-formed nutrients. indicates most effective mechanism capable reducing However, poor correlations atmospheric CO2 variability recorded cores, particularly CO2response rapid meltback event, our study sites same time Antarctic Isotopic 2, suggest Sea did not play controlling role variation glacial.