Using Legacy Data to Explore the Onset and Development of the Southern Hemisphere Supergyre

The Southern Hemisphere Supergyre refers to the strong connections and intertwining of the southern subtropical gyres. Tasman Leakage is a fundamental part of the supergyre, as well as of the  global thermohaline circulation, as it provides a return flow from the Pacific and Indian Oceans to the North Atlantic at intermediate depths.   However, both are only relatively recently documented, and the timing and conditions of onset are not well understood.This study characterizes the newly identified onset of Tasman Leakage in sedimentary records in and around the Indian Ocean using core descriptions and data derived from sediments.  Since much of this is legacy core material, core photographs were used to develop complementary and more continuous records to help refine the timing of onset.  These newly constructed time series based on core photographs are compared with X-ray Fluorescence time series based on core scanning provide both insight into onset of Tasman Leakage and a first test of the utility of time series based on core photos.This effort will focus on the intermediate water pathway associated with Tasman Leakage and identify conditions at critical around the basin from at least 8 Ma at Broken Ridge and Mascarene Plateau to understand the role of Indian Ocean intermediate waters in the Southern Hemisphere Supergyre in major climate events of the late Miocene. This proposed work provides the first synoptic view of SHS onset using intermediate depth cores, which in turn will provide an important framework for basin-wide synthesis of Indian Ocean drilling, much of which is outside of the main pathway of the SHS.  It will also serve as a test of the utility of legacy material as primary data.