(Table S1) Age determination of sediment cores SK99_17 and MD76-131

Productivity in the Arabian Sea is one of the highest in the world. It is controlled by seasonally reversing monsoonal wind-driven upwelling of nutrient-rich deeper waters which fuel phytoplankton growth. The detailed history of upwelling-induced productivity in the eastern Arabian Sea is unknown. Here we present paleoproductivity records from a composite sediment core at the millennial scale during the last 80 kyr B.P. These records are based on relative abundance counts of planktonic foraminifera and organic carbon contents, which are shown to mainly vary in concert. The eastern Arabian Sea upwelling-induced productivity was higher in the glacial period than in the Holocene, but it fell repeatedly on millennial timescales. These productivity declines occurred during cold events in the North Atlantic region, with the most pronounced changes prevailing during the Heinrich events. Hence, seasonal monsoon winds that drive upwelling-induced productivity in the east were weak when the North Atlantic was cold. These weak winds resulted in stratification of the water column, comparable to today's Arabian Sea stratification in the intermonsoonal period. Combining the new eastern with published western Arabian Sea results shows that the entire biological factory was severely diminished during the North Atlantic Heinrich events, and the seasonal productivity change in the Arabian Sea monsoon system was reduced with year-round low productivity.阿拉伯海的海洋生产力位居全球前列，其驱动机制为季风驱动的季节性反向上升流——该过程将富含营养物质的深层海水带至表层，为浮游植物的生长提供充足养分。目前学界对阿拉伯海东部海域上升流驱动的海洋生产力的详细演化历史仍不明确。本研究基于末次冰期以来距今8万年（80 kyr B.P.）的复合沉积物岩心，构建了千年尺度的古生产力记录（paleoproductivity records）。该记录基于浮游有孔虫（planktonic foraminifera）相对丰度计数与有机碳含量分析，二者的变化趋势整体一致。研究显示，阿拉伯海东部海域冰期的上升流驱动生产力高于全新世（Holocene），但在千年时间尺度上多次出现生产力下降事件。这类生产力下降事件与北大西洋区域的冷期事件同步发生，其中以海因里希事件（Heinrich events）期间的变化最为显著。由此可见，当北大西洋处于冷期时，驱动阿拉伯海东部上升流的季节性季风环流偏弱。这种偏弱的季风会导致水体层化现象加剧，与现今阿拉伯海季风间歇期的水体层化特征相似。将本研究获得的阿拉伯海东部海域数据与已发表的西部海域研究结果相结合后可见，在北大西洋海因里希事件期间，整个阿拉伯海的生物生产系统均出现严重衰退，季风系统驱动的季节性生产力变化被显著削弱，整体呈现全年低生产力状态。