Pore Fluid Constraints on the Temperature and Oxygen Isotopic Composition of the Glacial Ocean

Pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical Atlantic indicate that the oxygen isotopic composition (δ18O) of seawater at this site during the last glacial maximum was 0.8 ± 0.1 per mil higher than it is today. Combined with the δ18O change in benthic foraminifera from this region, the elevated ratio indicates that the temperature of deep water in the tropical Atlantic Ocean was 4°C colder during the last glacial maximum. Extrapolation from this site to a global average suggests that the ice volume contribution to the change in δ18O of foraminifera is 1.0 per mil, which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from Barbados corals and terrestrial climate proxies.

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