Marine isotope stage M2 (~3.3 Ma) in the southern hemisphere: constraining the climatic drivers of a short-term glaciation event during the mid-Pliocene warm Period.
Final Report Abstract
The movement of tectonic plates causes seaways to open and close throughout Earth’s geologic history. The Australian tectonic plate, for example, is moving north at a rate of several cm’s per year. On a million-year time scale, this movement induces the progressive restriction of the Indonesian Seaway and thus gradually restrains the flow of warm surface currents from the Pacific Ocean into the Indian Ocean. Previous research showed that a significant restructuring of the Indonesian seaway took place during the Pliocene (4 – 3 Ma). Interestingly, this period of Indonesian seaway reorganization and restriction coincides with a period of exceptional global climate variability: A brief (<100 kyr) but intense glaciation (Marine Isotope Stage (MIS) M2) interrupted the relatively warm climate of the Pliocene around 3.3 Ma. Different authors suggested a causal link between the restriction of the Indonesian seaway and global climate variability, and proposed that reduced heat transfer between the Pacific and Indian Oceans through the Indonesian seaway could contribute to global cooling. In this project, we evaluated this hypothesis by generating a ~2 kyr resolution planktonic δ18O record for the 3.7 - 2.8 Ma interval for Site U1463. Site U1463 was drilled during IODP Expedition 356 “Indonesian Throughflow” in September 2015 on the Northwestern Australian Shelf, and is located exactly at the outflow of the Indonesian seaway. When compared to the existing planktonic δ18O record from Site 806 in the eastern equatorial Pacific, the newly generated record for Site U1463 shows very similar values and patterns throughout the studied interval, both during warm and cold periods. This was rather surprising, as this result suggests no significant change in heat transfer between the Pacific and Indian Ocean during periods of global cooling, like MIS M2. However, when compared to the δ18O record from Site 763, just a few hundred kilometers further offshore than U1463, both records overlap throughout most of the studied interval, except for a ~130 kyr interval in the run-up to and during MIS M2. These patterns suggest that during this ~130 kyr interval, the warm Indonesian Throughflow waters were could still reach U1463, but no longer Site 763. In other words, we conclude that the Indonesian Throughflow was reduced in strength during MIS M2 but did not shut down completely. Our results thus support the hypothesis that a reduction in Pacific-to-Indian-Ocean heat transfer contributed to Pliocene glacial-interglacial variability on orbital timescales. IODP Expedition 356 “Indonesian Throughflow” yielded excellent and unique climate archives, providing a long-term history of how rainfall and aridity changed in Western Australia from 16 million years ago until today. This reconstruction of past climate change has been communicated to the wider public through MARUM’s press office (https://www.marum.de/Entdecken/Klimawandelverschiebt-Westwindzone.html), has been picked up by phys.org (https://phys.org/news/2017-05-shelf-sediments-reveal-climate-shifts.html), and was mentioned in 18 twitter messages (including ECORD, IODP at Texas A&M and University of Massachusetts Biogeochemistry department).
Publications
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(2017) Indonesian Throughflow drove Australian climate from humid Pliocene to arid Pleistocene. Geophysical Research Letters 44, 6914-6925
Christensen B.A., Renema W., Henderiks J., De Vleeschouwer D., Groeneveld J., Castañeda I.S., Reuning L., Bogus K., Auer G., Ishiwa T., McHugh C.M., Gallagher S.J., Fulthorpe C.S. and Expedition 356 scientists
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(2017). Australian shelf sediments reveal shifts in Miocene Southern Hemisphere Westerlies. Science Advances 3(5): e1602567
Groeneveld J., Hendriks J., Renema W., McHugh C.M., De Vleeschouwer D., Christensen B.A., Fulthorpe C.S., Reuning L., Gallagher S., Bogus K., Auer G., Ishiwa T. and Expedition 356 scientists
