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Holocene shifts of the southern westerlies across the South Atlantic

机译：整个南大西洋南部西风的全新世转移

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摘要

The southern westerly winds (SWW) exert a crucial influence over the world ocean and climate. Nevertheless, a comprehensive understanding of the Holocene temporal and spatial evolution of the SWW remains a significant challenge due to the sparsity of high-resolution marine archives and appropriate SWW proxies. Here we present a north-south transect of high-resolution planktonic foraminiferal oxygen isotope records from the western South Atlantic. Our proxy records reveal Holocene migrations of the Brazil-Malvinas Confluence (BMC), a highly sensitive feature for changes in the position and strength of the northern portion of the SWW. Through the tight coupling of the BMC position to the large-scale wind field, the records allow a quantitative reconstruction of Holocene latitudinal displacements of the SWW across the South Atlantic. Our data reveal a gradual poleward movement of the SWW by about 1-1.5 degrees from the early to the mid-Holocene. Afterward, variability in the SWW is dominated by millennial scale displacements on the order of 1 degrees in latitude with no recognizable longer-term trend. These findings are confronted with results from a state-of-the-art transient Holocene climate simulation using a comprehensive coupled atmosphere-ocean general circulation model. Proxy-inferred and modeled SWW shifts compare qualitatively, but the model underestimates both orbitally forced multimillennial and internal millennial SWW variability by almost an order of magnitude. The underestimated natural variability implies a substantial uncertainty in model projections of future SWW shifts.
机译：南部的西风（SWW）对世界海洋和气候产生至关重要的影响。然而，由于高分辨率海洋档案的稀疏性和适当的SWW代理，对SWW的全新世时空演变的全面了解仍然是一个重大挑战。在这里，我们介绍了南大西洋西部的高分辨率浮游有孔虫氧同位素记录的南北横断面。我们的代理记录显示，巴西-马尔维纳斯汇合处（BMC）的全新世迁徙是SWW北部位置和强度变化的高度敏感特征。通过将BMC位置与大型风场紧密耦合，记录可以定量重建南大西洋上空SWW的全新世纬向位移。我们的数据显示，从全新世早期到中期，SWW逐渐向极移动约1-1.5度。之后，SWW的变化主要由千分之一度的纬度位移所控制，没有长期趋势可辨。这些发现与最新的瞬态全新世气候模拟结果相吻合，该模拟使用了全面的大气-海洋总体环流耦合模型。代理推断和模型化的SWW变化在质量上进行比较，但是该模型低估了轨道强迫的千禧世代和内部千禧世代SWW的变化近一个数量级。被低估的自然可变性意味着未来SWW转换的模型预测中存在很大的不确定性。

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