Abstract The western tropical Atlantic (WTA) supplies warm and saline waters to the upper-limb of the Atlantic Meridional Overturning Circulation (AMOC) and may store excess heat and salinity during periods of AMOC slowdown. Since previous sea surface temperature (SST) reconstructions from the WTA typically focus on the Last Glacial Maximum and the last deglaciation, additional long-term records spanning multiple glacial-interglacial transitions are needed in order to elucidate the drivers of long-term WTA SST variability. We performed Mg/Ca analyses on the surface-dwelling planktic foraminifera Globigerinoides ruber (pink) from a sediment core raised from the southern WTA to reconstruct SST changes over the past 322 kyr. We evaluate the relative importance of atmospheric pCO2, AMOC strength and trade-wind intensity in driving the thermal evolution of the WTA across three glacial-interglacial cycles. Our results indicate a lack of pronounced glacial-interglacial variability in the SST record, prompting us to exclude atmospheric pCO2 as a direct driver of SST variations in the southern WTA. Similarly, we conclude that variations in AMOC strength also likely did not have a strong influence on long-term WTA SST, based on the low and relatively stable interhemispheric SST gradient over the past 322 kyr. Our results reveal high-amplitude variability in zonal SST gradients within the (sub)tropical South Atlantic and similarities between the long-term patterns of the intrahemispheric meridional SST gradient and our SST record. Based on these findings, we propose that changes in the intrahemispheric meridional SST gradient modulate southeast trade wind intensity, which in turn drives variations in zonal SST gradients and southern WTA SSTs.

中文翻译：

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三个冰期-间冰期循环对西热带南大西洋海面温度的强迫

摘要 热带西部大西洋 (WTA) 向大西洋经向翻转环流 (AMOC) 的上肢提供温暖和咸水，并可能在 AMOC 减速期间储存过多的热量和盐分。由于之前 WTA 的海面温度 (SST) 重建通常侧重于末次盛冰期和末次冰消期，因此需要跨越多次冰期-间冰期过渡的额外长期记录，以阐明 WTA SST 长期变化的驱动因素. 我们对来自 WTA 南部的沉积岩心的表面居住的浮游有孔虫 Globigerinoides ruber（粉红色）进行了 Mg/Ca 分析，以重建过去 322 kyr 的 SST 变化。我们评估大气 pCO2 的相对重要性，AMOC 强度和信风强度在三个冰期-间冰期循环中驱动 WTA 热演化。我们的结果表明 SST 记录中缺乏明显的冰期-间冰期变化，这促使我们排除大气 pCO2 作为南 WTA 海温变化的直接驱动因素。同样，基于过去 322 kyr 的低且相对稳定的半球间 SST 梯度，我们得出结论，AMOC 强度的变化也可能对长期 WTA SST 没有强烈影响。我们的结果揭示了（亚）热带南大西洋内纬向 SST 梯度的高幅度变化，以及半球内经向 SST 梯度的长期模式与我们的 SST 记录之间的相似性。基于这些发现，