Late Miocene Onset of Tasman Leakage and Southern Hemisphere Supergyre Ushers in Near‐Modern Circulation

This study provides a Miocene‐to‐recent history of Tasman Leakage (TL), driving surface‐to‐intermediate waters from the Pacific into the Indian Ocean. TL, in addition to Indonesian ThroughFlow (ITF), constitutes an important part of the Southern Hemisphere Supergyre. Here, we employ deep‐sea benthic δ 13 C timeseries from the southwestern Pacific and eastern Indian Oceans to identify the history of Tasman Leakage. The δ 13 C results combined with sedimentary evidence show that an inter‐ocean connection south of Australia existed from 7 Ma onward. A southward shift in Westerlies combined with a northward movement of Australia created the oceanic corridor necessary for Tasman Leakage (between Australia and the sub‐Antarctic Front) at this time. Furthermore, changes in the northern limb of the Supergyre (ITF) are evident in the sedimentary record on Broken Ridge from ∼3 to 2 Ma when Banda Sea intermediate waters started originating from the North Pacific.