The amplifying effect of Indonesian Throughflow heat transport on Late Pliocene Southern Hemisphere climate cooling
The amplifying effect of Indonesian Throughflow heat transport on Late Pliocene Southern Hemisphere climate cooling
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DOI：
10.1016/j.epsl.2018.07.035
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发表时间：
2018-10-15
影响因子：
5.3
通讯作者：
Paelike, Heiko
中科院分区：
文献类型：
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作者：
De Vleeschouwer, David;Auer, Gerald;Paelike, Heiko
一个异常短暂的冰川中断了温暖的上新世约3.3马（海洋同位素阶段（MIS）M2）。有不同的假设来解释为什么这次冰川事件如此明显，以及为什么全球气候系统在之后相对较快地恢复到上新世温暖的条件。这些建议的机制之一是减少赤道到极点的热传递，在响应构造减少印尼的对流（ITF）。ITF是全球温盐海洋环流的重要组成部分，将热量从印度-太平洋暖池输送到印度洋。当ITF连通性降低时，沿着沿着澳大利亚西海岸向极地流动的Leeuwin海流的水和热供应也会减少。为了评估上新世中期冰川和纬度之间的关系，通过印度尼西亚的对流热输送，我们建立了一个多代理轨道尺度记录的3.7-2.8 Ma的间隔从国际海洋发现计划（IODP）网站U1463，澳大利亚西北部。站点U1463记录与附近站点763和西太平洋暖池站点806的古气候记录的比较允许上新世古海洋学的详细区域重建，从而用于测试所提出的假设。晚上新世U1463的钾含量以天文速度下降为特征，记录了澳大利亚西北部的干旱程度增加，并在夏季太阳辐射最大值下被加强的夏季季风降水周期性地缓解。3180记录的浮游有孔虫Globigerinoides sacculifer相关非常好的海表温度（SST）记录从网站806在西太平洋暖池，即使在MIS M2。因此，站点U1463即使在上新世冰期也保留了不间断的ITF信号。然而，U1463 delta O-18（G.sacculifer）记录与MIS M2附近的763 A站点记录显示出0.5ppm的偏移。这意味着在U1463以西约500公里处的763 A站点更密切地跟踪了MIS M2上的印度洋SST记录。U1463的数据显示，通过印尼对流的热量输送在MIS M2期间并没有完全停止，而是在MIS M2之前和期间强度下降，导致763 A站点暂时反映了印度洋，而不是ITF信号。我们的结论是ITF的变化显着影响纬向热量输送的Leeuwin电流的装置，因此有助于MIS M2的相对强度。我们提出的ITF阀之间的太平洋和印度洋作为一个正反馈机制，其中初始海平面下降减少ITF热传输，反过来放大全球冷却推进南极洲的热隔离。(C)2018 Elsevier B. V.版权所有。
An unusually short glaciation interrupted the warm Pliocene around 3.3 Ma (Marine Isotope Stage (MIS) M2). Different hypotheses exist to explain why this glaciation event was so pronounced, and why the global climate system returned to warm Pliocene conditions relatively quickly afterwards. One of these proposed mechanisms is a reduced equator-to-pole heat transfer, in response to a tectonically reduced Indonesian Throughflow (ITF). The ITF is a critical part of the global thermohaline ocean circulation, transporting heat from the Indo-Pacific Warm Pool to the Indian Ocean. When ITF connectivity is reduced, the water and heat supply for the Leeuwin Current, flowing poleward along Australia's west coast, is also diminished. To assess the possible relationship between mid-Pliocene glaciations and latitudinal heat transport through the Indonesian Throughflow, we constructed a multi-proxy orbital scale record for the 3.7-2.8 Ma interval from International Ocean Discovery Program (IODP) Site U1463, off northwest Australia. The comparison of the Site U1463 record with paleoclimate records from nearby Site 763 and West Pacific Warm Pool Site 806 allows for a detailed regional reconstruction of Pliocene paleoceanography and thus for testing the proposed hypothesis. An astronomically-paced decrease in potassium content characterizes the late Pliocene interval of U1463.This record documents the increasing aridity of northwest Australia, periodically alleviated by reinforced summer monsoon precipitation under summer insolation maxima. The 3180 record of the planktonic foraminifer Globigerinoides sacculifer correlates exceptionally well with the sea surface temperature (SST) record from Site 806 in the West Pacific Warm Pool, even during MIS M2. Hence, Site U1463 preserves an uninterrupted ITF signal even during Pliocene glaciations. However, the U1463 delta O-18(G.sacculifer) record exhibits a 0.5 parts per thousand offset with the nearby Site 763A record around MIS M2. This implies that Site 763A, about 500 km west of U1463, more closely tracks Indian Ocean SST records across MIS M2. The U1463 data reveal that heat-transport through the Indonesian Throughflow did not shut down completely during MIS M2, but rather its intensity decreased prior to and during MIS M2, causing Site 763A to temporarily reflect an Indian Ocean, rather than an ITF signal. We conclude that ITF variability significantly influenced latitudinal heat transport by means of the Leeuwin Current and hence contributed to the relative intensity of MIS M2. We propose the ITF valve between the Pacific and Indian Ocean as a positive feedback mechanism, in which an initial sea level lowering reduces ITF heat transport, in turn amplifying global cooling by advancing the thermal isolation of Antarctica. (C) 2018 Elsevier B.V. All rights reserved.