Holocene shifts of the southern westerlies across the South Atlantic
Holocene shifts of the southern westerlies across the South Atlantic
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DOI：
10.1002/2014pa002677
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发表时间：
2015-02
期刊：
影响因子：
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通讯作者：
I. Voigt;C. Chiessi;M. Prange;S. Mulitza;J. Groeneveld;V. Varma;Ruediger Henrich
中科院分区：
文献类型：
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作者：
I. Voigt;C. Chiessi;M. Prange;S. Mulitza;J. Groeneveld;V. Varma;Ruediger Henrich
南方西风对世界海洋和气候产生了至关重要的影响。然而，由于高分辨率海洋档案和适当的海洋水资源替代资料稀少，全面了解海洋水资源的全新世时空演变仍然是一项重大挑战。在这里，我们展示了南大西洋西部高分辨率浮游有孔虫氧同位素记录的南北断面。我们的代理记录揭示了巴西-马尔维纳斯交汇处(BMC)的全新世迁移，这是一个对西南偏北部分位置和强度变化高度敏感的特征。通过BMC位置与大尺度风场的紧密耦合，这些记录可以定量重建南大西洋西南偏西全新世的纬向位移。我们的数据显示，从全新世早期到中期，西南向逐渐向极移动了约1-1.5°。此后，SWW的变化主要是由纬度约1°的千禧年尺度位移主导的，没有明显的长期趋势。这些发现与使用综合大气-海洋耦合环流模式进行的最先进的全新世气候瞬变模拟的结果相抵触。代理推断的和模拟的SWW漂移在定性上进行了比较，但该模型将轨道强迫的多年SWW变率和内部千禧年SWW变率低估了近一个数量级。被低估的自然变异性意味着对未来西南偏西变化的模型预测存在很大的不确定性。
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° from the early to the mid-Holocene. Afterward, variability in the SWW is dominated by millennial scale displacements on the order of 1° 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.