TEX86H proxy and BIT index of sediment core GeoB9528-3 and reconstructed temperature data from NW Africa surface sediments

Changes in the strength of Atlantic meridional overturning circulation (AMOC) are known to have profound impacts on global climate. Coupled modelling studies have suggested that, on annual to multi-decadal time scales, a slowdown of AMOC causes a deepening of the thermocline in the tropical Atlantic. However, this process has been poorly constrained by sedimentary geochemical records. Here, we reconstruct surface (UK'37 Index) and thermocline (TEX86H) water temperatures from the Guinea Plateau Margin (Eastern tropical Atlantic) over the last two glacial-interglacial cycles (~ 192 kyr). These paleotemperature records show that periods of reduced AMOC, as indicated by the d13 C benthic foraminiferal record from the same core, coincide with a reduction in the near-surface vertical temperature gradient, demonstrating for the first time that AMOC-induced tropical Atlantic thermocline adjustment exists on longer, millennial time scales. Modelling results support the interpretation of the geochemical records and show that thermocline adjustment is particularly pronounced in the eastern tropical Atlantic. Thus, variations in AMOC strength appear to be an important driver of the thermocline structure in the tropical Atlantic from annual to multi-millennial time scales.大西洋经向翻转环流（Atlantic meridional overturning circulation, AMOC）强度的变化，已知会对全球气候造成深远影响。耦合模式研究表明，在年际至数十年的时间尺度上，AMOC的减缓会导致热带大西洋温跃层加深。然而，这一过程此前鲜有沉积地球化学记录的有效约束。本研究基于东热带大西洋几内亚高原陆缘的沉积岩芯，重建了过去两个冰期-间冰期旋回（约192 kyr）内的表层水温（UK'37指标，UK'37 Index）与温跃层水温（TEX86H指标，TEX86H）记录。这些古温度记录显示，与同一岩芯的底栖有孔虫碳同位素（δ¹³C）记录所指示的AMOC减弱期相吻合的，是近表层垂直温度梯度的降低，这首次证实了AMOC驱动的热带大西洋温跃层调整存在于更长的千年时间尺度上。模式结果佐证了地球化学记录的解释，并表明温跃层调整在东热带大西洋区域尤为显著。因此，从年际至千年时间尺度来看，AMOC强度的变化似乎是热带大西洋温跃层结构的重要驱动因子。