Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA.
Institute at Brown for Environment and Society, Brown University, Providence, RI, USA.
Sci Adv. 2023 Jan 4;9(1):eadd4909. doi: 10.1126/sciadv.add4909.
Abrupt changes in the Atlantic meridional overturning circulation (AMOC) are thought to affect tropical hydroclimate through adjustment of the latitudinal position of the intertropical convergence zone (ITCZ). Heinrich Stadial 1 (HS1) involves the largest AMOC reduction in recent geological time; however, over the tropical Indian Ocean (IO), proxy records suggest zonal anomalies featuring intense, widespread drought in tropical East Africa versus generally wet but heterogeneous conditions in the Maritime Continent. Here, we synthesize proxy data and an isotope-enabled transient deglacial simulation and show that the southward ITCZ shift over the eastern IO during HS1 strengthens IO Walker circulation, triggering an east-west precipitation dipole across the basin. This dipole reverses the zonal precipitation anomalies caused by the exposed Sunda and Sahul shelves due to glacial lower sea level. Our study illustrates how zonal modes of atmosphere-ocean circulation can amplify or reverse global climate anomalies, highlighting their importance for future climate change.
北大西洋经向翻转环流（AMOC）的突然变化被认为会通过调整热带辐合带（ITCZ）的纬度位置来影响热带气候。 Heinrich 盛冰期 1（HS1）涉及到最近地质时期 AMOC 的最大减少；然而，在热带印度洋（IO）上，代理记录表明，与海洋大陆普遍湿润但不均匀的条件相比，东非热带地区存在强烈、广泛干旱的纬向异常。在这里，我们综合了代理数据和同位素启用的瞬态去冰期模拟，表明在 HS1 期间，IO 东部的 ITCZ 南移加强了 IO 沃克环流，引发了整个盆地的东西向降水偶极子。这种偶极子逆转了由于冰期海平面降低而导致的苏门答腊和澳大利亚大陆暴露的赤道降水异常。我们的研究说明了大气-海洋环流的纬向模态如何放大或反转全球气候异常，突出了它们对未来气候变化的重要性。
