The amplifying effect of Indonesian Throughflow heat transport on Late Pliocene Southern Hemisphere climate cooling

Stepwise Weakening of the Pliocene Leeuwin Current

“…Here, we compare the high‐resolution δ 18 O G.sacculifer record of U1459 to its contemporaneous counterparts at Site 763 (Exmouth Plateau) and Site U1463 (Northwest Shelf) between 3.9 and 3.1 Ma. The latter two sites, both north of the Northwest Cape, have nearly identical isotopic signatures during the studied time slice (De Vleeschouwer et al, ). Their isotopic offset with U1459 ranges between 0.8‰ and 2‰ and is independent of global changes in ice volume, as the associated changes in the δ18O sw would affect all sites equally (Figures a and c).…”

Timing and Pacing of Indonesian Throughflow Restriction and Its Connection to Late Pliocene Climate Shifts

“…Modeling studies suggest that ITF variability has a major influence on ocean heat distribution (Brierley & Fedorov, ; Cane & Molnar, ; Di Nezio et al, ; Jochum et al, ), yet its contribution to the global climatic evolution is difficult to resolve due to the tectonic complexity of the Indonesian Archipelago (Brierley & Fedorov, ; Gordon et al, ; Gordon & Kamenkovich, ; Holbourn et al, ; Kuhnt et al, ; Spooner et al, ; Susanto & Song, ). Generally, ITF restriction is likely driven by two distinct mechanisms: (1) sea level‐driven restriction leading to the emergence of shelf areas restricting the ITF paths only to the deep marine troughs during glacial intervals (De Vleeschouwer et al, ; Di Nezio et al, ; Holbourn et al, ; Xu et al, , ; Zuraida et al, ); and (2) geometric reorganization of the Indonesian Gateway system caused by tectonic activity linked to the northward movement of the Australasian Plate and the related collision with the Eurasian Plate (Cane & Molnar, ; Christensen et al, ; Karas et al, ; Kuhnt et al, ; Molnar & Cronin, ; Sarnthein et al, ).…”

“…There is evidence suggesting that an important uplift phase began during the Late Miocene to Early Pliocene (Cane & Molnar, ; Hall, ; Hall et al, ; Kuhnt et al, ; Molnar & Cronin, ; Tate et al, ), with tectonic restriction of the ITF having a major effect on global thermohaline circulation by the late Early Pliocene (Cane & Molnar, ; Gallagher et al, ; Karas et al, , ; Karas et al, ). The ITF reorganization during the Pliocene has also been causally linked to the marine isotope stage (MIS) M2 glacial event at ~3.3 Ma (Brigham‐Grette et al, ; De Schepper et al, , ; Lisiecki & Raymo, ) with modeling and paleoceanographical studies showing that tectonic ITF restriction had major effects on global climate by changing the heat exchange between the Pacific and the Indian Oceans (Cane & Molnar, ; De Schepper et al, ; De Vleeschouwer et al, ; Gallagher et al, ; Gallagher et al, ; Karas et al, , ; Karas et al, ; Molnar & Cronin, ; Sarnthein et al, ). The MIS M2 event is of particular interest as it represents a well‐recognized feature of global benthic oxygen isotope records of both the LR04 stack (Lisiecki & Raymo, ) and DV17 mega splice (De Vleeschouwer et al, ).…”

“…In this study we present a multiproxy data set spanning the Early to Late Pliocene (~3.66 to 2.98 Ma) from International Ocean Discovery Program (IODP) Expedition 356 Site U1463 (Gallagher et al, ), situated on the Australian northwest shelf (NWS) within the path of the Leeuwin Current (LC), and directly influenced by the ITF (D'Adamo et al, ; Wijeratne et al, ). The high recovery of material at Site U1463 (Christensen et al, ; De Vleeschouwer et al, ; Gallagher et al, ) permits the reconstruction of high‐resolution record of Pliocene downstream ITF variability along the NWS. Geophysical borehole records and sedimentological data from Expedition 356 have already proven instrumental in detailing the long‐term climatic evolution of Australia throughout the Neogene (Christensen et al, ; Groeneveld et al, ).…”

“…Geophysical borehole records and sedimentological data from Expedition 356 have already proven instrumental in detailing the long‐term climatic evolution of Australia throughout the Neogene (Christensen et al, ; Groeneveld et al, ). Here we elucidate surface water conditions along the NWS in the critical Pliocene time interval between 3.5 and 3 Ma, when tectonic ITF restriction is proposed to have significantly altered the ITF (Cane & Molnar, ; Christensen et al, ; De Vleeschouwer et al, ; Gourlan et al, ; Karas et al, ; Le Houedec et al, ). We applied an integrated approach using paleobiological (calcareous nannofossil assemblages), geochemical (planktic foraminifer stable isotopes and bulk organic carbon, sulfur, and carbonate content), and geophysical data including calibrated spectral gamma ray and X‐ray fluorescence (XRF) elemental data (De Vleeschouwer et al, ) to reconstruct environmental changes along the NWS and link them to contemporary climatic records in the region (Karas et al, , ; Wara et al, ).…”