Pliocene Indonesian Throughflow and Leeuwin Current dynamics: Implications for Indian Ocean polar heat flux
Pliocene Indonesian Throughflow and Leeuwin Current dynamics: Implications for Indian Ocean polar heat flux
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DOI：
10.1029/2010pa001949
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发表时间：
2011-06-01
期刊：
影响因子：
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通讯作者：
Garbe-Schoenberg, Dieter
中科院分区：
文献类型：
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作者：
Karas, Cyrus;Nuernberg, Dirk;Garbe-Schoenberg, Dieter
要理解上新世中期（3.5-2.5 Myr前）全球逐渐变冷，需要考虑热带海道的构造收缩，这影响了海洋环流和气候演变。本文通过对浮游有孔虫的δ O-18和Mg/Ca比值的成对测量，重建了热带印度洋西部（站点709C）上新世的水文特征，以及亚热带印度洋东部（站点763A） Leeuwin洋流对印度尼西亚门户动力学的响应。今天，印度尼西亚通流（ITF）和随后从西澳大利亚向南流动的温暖的Leeuwin洋流对印度洋的极地热输送至关重要。在3.5-3 Ma期间，Leeuwin海流区域的海表温度显著下降，大约3.3 Ma，比热带印度洋东部和西部的海表温度低2 -3℃。我们认为，海面温度的下降是由于构造性地表ITF减少导致的卢因流减弱，对西澳大利亚造成了严重的气候影响。我们认为，这种表面ITF的减少导致印度洋向极地热输送的减少，导致Leeuwin流减弱，并可能导致Benguela上升流系统的冷却。
To understand the gradual global cooling during the mid-Pliocene (3.5-2.5 Myr ago) one needs to consider the tectonical constriction of tropical seaways, which affected ocean circulation and the evolution of climate. Here we use paired measurements of delta O-18 and Mg/Ca ratios of planktonic foraminifera to reconstruct the Pliocene hydrography of the western tropical Indian Ocean (Site 709C) and changes in the Leeuwin Current in the eastern subtropical Indian Ocean (Site 763A) in response to Indonesian Gateway dynamics. Today, the Indonesian Throughflow (ITF) and, subsequently, the warm southward flowing Leeuwin Current off Western Australia are essential for the polar heat transport in the Indian Ocean. During 3.5-3 Ma, sea surface temperatures significantly dropped in the Leeuwin Current area, becoming since similar to 3.3 Ma 2 degrees C-3 degrees C cooler than the rather unchanged sea surface temperatures from the eastern and western tropical Indian Ocean. We refer this drop in sea surface temperatures to a weakened Leeuwin Current with severe climatic effects on Western Australia induced by a tectonically reduced surface ITF. We suggest that this reduced surface ITF led to a diminished poleward heat transport in the Indian Ocean resulting in a weakened Leeuwin Current and possibly to cooling of the Benguela upwelling system.