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    Indonesian throughflow controlled the westward extent of the Indo-Pacific Warm Pool during glacial-interglacial intervals

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    Global_Planetary_Change_183_103031a.pdf (973.5Kb)
    Date
    2019
    Author
    Saraswat, R.
    Singh, D.P.
    Lea, D.W.
    Mackensen, A.
    Naik, D.K.
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    Abstract
    The tropical atmospheric circulation is strongly influenced by the sea surface temperature (SST) of the warmest region of the world ocean, the Indo-Pacific Warm Pool (IPWP). The effect of recent anomalous Indian Ocean warming on the extent of the IPWP remains uncertain. Past SST records from the tropical Indian Ocean, associated with different temporal boundary conditions, can help shed light on how climate change impacts the IPWP and associated monsoonal processes. Here, we reconstruct the seawater temperature and precipitation changes (from Mg/Ca and δ18O of surface-dwelling planktic foraminifera Globigerinoides ruber) of the last ~184 kyr BP from the westernmost margin of the IPWP. The data is then used to reconstruct the spatial extent and intensity of the IPWP structure as well as its relationship with other regional phenomena. A consistently warmer (>28 °C) central equatorial Pacific Ocean and significantly cooler equatorial western Pacific and the Indian Ocean suggests that the warm pool extent reduced considerably during MIS6 as well as the last glacial interval, leading to a strong La-Nina like condition. The most enriched seawater δ18O (δ18Osw) during MIS6, was in the westernmost IPWP, suggesting weakened precipitation, despite La-Lina like conditions. The westernmost part of the IPWP became warmer than the threshold 28 °C during MIS5e and the early Holocene, suggesting the westward extension of the IPWP. The eastern equatorial Pacific Ocean also warmed considerably during MIS5e, suggesting a weaker Walker Circulation and a stronger El-Nino. The difference in δ18Osw decreased considerably during MIS5e and is attributed to increased precipitation/freshwater runoff in the central equatorial Indian Ocean. The increase in δ18Osw (~1.5‰) between ~55 kyr until the last glacial maximum, in a majority of the Indian Ocean records, suggests progressively weakened precipitation. A majority of the records have a uniform SST anomaly throughout the Holocene. A warmer equatorial Indian Ocean during interglacials suggests a strong modulation of the IPWP extent by the transport of warm water through the Indonesian throughflow region. The large drop in δ18Osw despite the comparable change in SST during the last glacial interval suggests that monsoon forcing has been much stronger in altering the surface hydrography in the Indian Ocean than the central Pacific Ocean.
    URI
    https://doi.org/10.1016/j.gloplacha.2019.103031
    http://drs.nio.org/drs/handle/2264/8211
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