Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Douglas, Peter M. J., Affek, Hagit P., Ivany, Linda C., Houben, Alexander J. P., Sijp, Willem P., Sluijs, Appy, Schouten, Stefan, Pagani, Mark
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: National Academy of Sciences 2014
• Subjects: paleooceanography; clumped isotopes; organic geochemistry; climate modeling; high-latitude climate; Antarctic; The Antarctic; Antarctic Peninsula; Ross Sea; Pacific; Seymour; Seymour Island; Antarc*
• Online Access: https://doi.org/10.1073/pnas.1321441111; https://www.ncbi.nlm.nih.gov/pmc/PMC4020054

Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10–17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands. © 2014 National Academy of Sciences. Published online before print April 21, 2014. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved March 21, 2014 (received for review November 15, 2013). Gerard Olack, Dominic Colosi, and Glendon Hunsinger provided assistance with clumped isotope ...