Corals Reveal an Unprecedented Decrease of Arabian Sea Upwelling During the Current Warming Era

Upwelling in the Arabian Sea driven by the Indian summer monsoon pumps deep, cold, and eutrophic seawater to the sea surface every summer. The Indian summer monsoon and the Arabian Sea upwelling were expected to intensify with global warming, following the hypothesis that the Eurasian landmass would warm faster than the Indian Ocean. Contrary to expectations, the northern Indian Ocean currently warms faster than the Indian subcontinent. A weakening of the Indian summer monsoon circulation is reported, which possibly weakens the Arabian Sea upwelling. However, a lack of observations limits understanding of current and historical changes of the Arabian Sea upwelling. Here, we reconstruct the Arabian Sea upwelling over the past millennium using modern and fossil corals. Our coral records show that the Arabian Sea upwelling intensity was very stable over the last millennium and unprecedentedly declines at present. Our finding implies anthropogenic forcing likely weakens the Arabian Sea upwelling.

每年夏季，由印度夏季风驱动的阿拉伯海上涌将深层、寒冷且富营养的海水泵至海面。按照欧亚大陆比印度洋升温更快的假设，预计随着全球变暖，印度夏季风和阿拉伯海上涌会增强。与预期相反，目前印度洋北部比印度次大陆升温更快。据报道，印度夏季风环流减弱，这可能使阿拉伯海上涌减弱。然而，观测的缺乏限制了对阿拉伯海上涌当前和历史变化的理解。在此，我们利用现代和化石珊瑚重建了过去千年的阿拉伯海上涌情况。我们的珊瑚记录显示，阿拉伯海上涌强度在过去千年中非常稳定，而目前却出现了前所未有的下降。我们的发现意味着人为强迫可能使阿拉伯海上涌减弱。