Enhanced Poleward Flux of Atmospheric Moisture to the Weddell Sea Region (ODP Site 690) During the Paleocene-Eocene Thermal Maximum

Earth's hydrological cycle was profoundly perturbed by massive carbon emissions during an ancient (56 Ma) global warming event referred to as the Paleocene-Eocene thermal maximum (PETM). One approach to gaining valuable insight into the response of the hydrological cycle is to construct sea-surface salinity (SSS) records that can he used to gauge changes in the rates of evaporation and precipitation during the PETM in such climatically sensitive areas as the circum-Antarctic region. Here, we pair oxygen isotope (delta O-18) and magnesium-calcium (Mg/Ca) measurements to reconstruct PETM sea-surface temperatures (SSTs) and delta O-18 composition of seawater (delta O-18(sw)) at austral Site 690 (Weddell Sea). Several discrepancies emerge between the delta O-18- and Mg/Ca-based SST records, with the latter indicating that the earliest PETM was punctuated by a short-lived similar to 4 degrees C increase in local SSTs. Conversion of the delta O-18(sw) values to SSS reveals a similar to 4 ppt decrease similar to 50 ka after peak PETM warming at Site 690. This negative SSS (delta O-18(sw)) anomaly coincides with a prominent minimum in the planktic foraminifer delta O-18 record published for the Site 690 PETM section. Thus, our revised interpretation posits that this delta O-18 minimum signals a decrease in surface-ocean delta O-18(sw) fostered by a transient increase in mean annual precipitation in the Weddell Sea region. The results of this study corroborate the view that the poleward flux of atmospheric moisture temporarily increased during a distinctive stage of the PETM.