Changes in low-latitude sea surface temperature (SST) has far reaching consequences on Earth’s radiative budget, hydrological cycle, and ecosystems. Yet records of low-latitude SST during warmer-than-modern climates across the Cenozoic (0 – 60 million years ago (Ma)) remain limited. Further, the acquisition of accurate SST estimates in the geological past has inherent weaknesses with traditionally applied proxies for temperature reconstruction subject to both biological and geochemical caveats. This has often resulted in diverging absolute and relative SSTs, impacting our ability to constrain changes in meridional and zonal temperature gradients and corresponding climate feedbacks fundamental to better understanding both the influence and sensitivity of the low-latitudes to changing boundary conditions and global climate change.
Across the past decade there has been a concentrated effort to develop and apply clumped isotope thermometry as a viable approach for ocean temperature reconstruction from foraminifera. This approach is thought to be outwith biological vital effects and the requisite assumptions regarding past seawater chemistry due to the clumping of 13C-18O bonds being dictated, in isolation of seawater chemistry, by thermodynamics. Thus, one of the aims of ELMO is to apply this proxy approach to provide additional constraints on reconstructing past SST from a low-latitude site across the Cenozoic. To complement and better understand proxy reconstruction methods, ELMO will reconstruct Mg/Ca-temperatures, the traditional approach to temperature reconstruction using foraminifera shell geochemistry, to provide a direct comparison between temperatures derived from clumped isotope analysis. In addition to reconstructing a long-term SST record, the oceanographic conditions of the targeted site (IODP U1443, southern Bay of Bengal) are influenced by monsoonal forcing from the Indian Monsoon system. A secondary aim of ELMO is thus, to identify if any changes in temperature variability gained from individual foraminifera trace element analysis (Mg/Ca) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) can provide additional insights on the onset and evolution of the modern Indian Monsoon system.
