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.