Coupled evolution of temperature and carbonate chemistry during the Paleocene-Eocene; new trace element records from the low latitude Indian Ocean
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The early Paleogene represents the most recent interval in Earth's history characterized by global greenhouse warmth on multi-million year timescales, yet our understanding of long-term climate and carbon cycle evolution in the low latitudes, and in particular the Indian Ocean, remains very poorly constrained. Here we present the first long-term sub-eccentricity-resolution stable isotope (δ13C and δ18O) and trace element (Mg/Ca and B/Ca) records spanning the late Paleocene-early Eocene (similar to 58-53 Ma) across a surface-deep hydrographic reconstruction of the northern Indian Ocean, resolving late Paleocene 405-kyr paced cyclicity and a portion of the PETM recovery. Our new records reveal a long-term warming of similar to 4-5 °C at all depths in the water column, with absolute surface ocean temperatures and magnitudes of warming comparable to the low latitude Pacific. As a result of warming, we observe a long-term increase in δ18Osw of the mixed layer, implying an increase in net evaporation. We also observe a collapse in the temperature gradient between mixed layer- and thermocline-dwelling species from similar to 57-54 Ma, potentially due to either the development of a more homogeneous water column with a thicker mixed layer, or depth migration of the Morozovellain response to warming. Synchronous warming at both low and high latitudes, along with decreasing B/Ca ratios in planktic foraminifera indicating a decrease in ocean pH and/or increasing dissolved inorganic carbon, suggest that global climate was forced by rising atmospheric CO2 concentrations during this time.
Barnet , J S K , Harper , D T , LeVay , L J , Edgar , K M , Henehan , M J , Babila , T L , Ullmann , C , Leng , M J , Kroon , D , Zachos , J C & Littler , K 2020 , ' Coupled evolution of temperature and carbonate chemistry during the Paleocene-Eocene; new trace element records from the low latitude Indian Ocean ' , Earth and Planetary Science Letters , vol. 545 , 116414 . https://doi.org/10.1016/j.epsl.2020.116414
Earth and Planetary Science Letters
DescriptionThis work was principally funded by a European Consortium for Ocean Research Drilling (ECORD) Research Grant, the International Association of Sedimentologists (IAS) Postgraduate Research Grant Scheme, and the Natural Environment Research Council (NERC) Isotope Geosciences Facility (IP-1581–1115), awarded to James Barnet and Kate Littler. LJL acknowledges funding from the IODP-JRSO (NSF grant 1326927), KME acknowledges funding from NERC grants NE/H016457/1 and NE/P013112/1, and CVU acknowledges funding via NERC grant NE/N018508/1.
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