High Arabian Sea productivity conditions during MIS 13 - odd monsoon event or intensified overturning circulation at the end of the Mid-Pleistocene transition?
High Arabian Sea productivity conditions during MIS 13 - odd monsoon event or intensified overturning circulation at the end of the Mid-Pleistocene transition?
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DOI：
10.5194/cp-6-63-2010
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发表时间：
2010-01
影响因子：
4.3
通讯作者：
M. Ziegler;L. Lourens;E. Tuenter;G. Reichart
中科院分区：
文献类型：
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作者：
M. Ziegler;L. Lourens;E. Tuenter;G. Reichart
抽象的。海洋同位素第13阶段(距今约50万年)在许多古气候记录中被认为是非典型的，特别是与整个北半球异常强烈的夏季风有关。在这里，我们提出了一项多代理研究，取自阿拉伯海北部中等水深的墨累岭沉积岩芯，覆盖了过去75万年。我们的结果表明，在阿拉伯海MIS13期间，初级生产力条件异常高，导致深海沉积物中极端的碳酸盐溶解和海绿石化作用。这些观测结果可以解释为营养丰富的深水由风驱动的上升流增加，因此，正如早期研究所建议的那样，在MIS13期间发生了一次异常强烈的夏季风事件。然而，来自南极洲的冰芯记录表明，在此期间，与热带湿地范围有关的大气甲烷浓度相对较低。这是对MIS13期间极端增强的全球季风环流的有力反对，而且与瞬变气候模拟实验的结果形成了鲜明对比。作为阿拉伯海记录中异常情况的另一种解决方案，我们提出，高初级生产力可能与中更新世过渡末期大西洋开始密集的经向翻转环流有关。这可能导致进入印度洋真光带的营养丰富的深水供应增加，从而触发观测到的最大生产力。
Abstract. Marine isotope stage (MIS) 13 (~500 000 years ago) has been recognized as atypical in many paleoclimate records and, in particular, it has been connected to an exceptionally strong summer monsoon throughout the Northern Hemisphere. Here, we present a multi-proxy study of a sediment core taken from the Murray Ridge at an intermediate water depth in the northern Arabian Sea that covers the last 750 000 years. Our results indicate that primary productivity conditions were anomalously high during MIS 13 in the Arabian Sea and led to extreme carbonate dissolution and glauconitization in the deep-sea sediments. These observations could be explained by increased wind driven upwelling of nutrient-rich deep waters and, hence, by the occurrence of an exceptionally strong summer monsoon event during MIS 13, as it was suggested in earlier studies. However, ice core records from Antarctica demonstrate that atmospheric methane concentrations, which are linked to the extent of tropical wetlands, were relatively low during this period. This constitutes a strong argument against an extremely enhanced global monsoon circulation during MIS 13 which, moreover, is in contrast with results of transient climate modelling experiments. As an alternative solution for the aberrant conditions in the Arabian Sea record, we propose that the high primary productivity was probably related to the onset of an intensive meridional overturning circulation in the Atlantic Ocean at the end of the Mid-Pleistocene transition. This may have led to an increased supply of nutrient-rich deep waters into the Indian Ocean euphotic zone, thereby triggering the observed productivity maximum.