Abstract. We present downcore records of redox-sensitive authigenic uranium (U) and manganese (Mn) concentrations based on five marine sediment cores spanning a meridional transect encompassing the Subantarctic and Antarctic zones in
the southwestern Indian Ocean covering the last glacial cycle. These records
signal lower bottom water oxygenation during glacial climate intervals and
generally higher oxygenation during warm periods, consistent with
climate-related changes in deep-ocean remineralized carbon storage. Regional
changes in the export of siliceous phytoplankton to the deep sea may have
entailed a secondary influence on oxygen levels at the water–sediment
interface, especially in the Subantarctic Zone. The rapid reoxygenation
during the deglaciation is in line with increased ventilation and enhanced
upwelling after the Last Glacial Maximum (LGM), which in combination
conspired to transfer previously sequestered remineralized carbon to the
surface ocean and the atmosphere, contributing to propel the Earth's climate out of the last ice age. These records highlight the still insufficiently documented role that the Southern Indian Ocean played in the air–sea partitioning
of CO2 on glacial–interglacial timescales.
Abstract. We present downcore records of redox-sensitive authigenic uranium (U) and manganese (Mn) concentrations based on five marine sediment cores spanning a meridional transect encompassing the Subantarctic and the Antarctic zones in the Southwest Indian Ocean covering the last glacial cycle. These records signal lower bottom water oxygenation during glacial climate intervals and generally higher oxygenation during warm periods, consistent with climate-related changes in deep ocean remineralised carbon storage. Regional changes in the export of siliceous phytoplankton to the deep-sea may have entailed a secondary influence on oxygen levels at the water-sediment interface, especially in the Subantarctic Zone. The rapid reoxygenation during the deglaciation is in line with increased ventilation and enhanced upwelling after the Last Glacial Maximum (LGM), which, in combination, conspired to transfer previously sequestered remineralised carbon to the surface ocean and the atmosphere, contributing to propel the Earth’s climate out of the last ice age. These records highlight the yet insufficiently documented role the southern Indian Ocean played in the air-sea partitioning of CO2 on glacial-interglacial timescales.
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