Prolonged warming of the Brazil Current precedes deglaciations
Prolonged warming of the Brazil Current precedes deglaciations
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DOI：
10.1016/j.epsl.2017.01.014
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发表时间：
2017-04
影响因子：
5.3
通讯作者：
T. P. Santos;D. Lessa;I. Venancio;C. Chiessi;S. Mulitza;H. Kuhnert;A. Govin;Thiago Machado;K. B. Costa;F. Toledo;B. Dias;A. Albuquerque
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文献类型：
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作者：
T. P. Santos;D. Lessa;I. Venancio;C. Chiessi;S. Mulitza;H. Kuhnert;A. Govin;Thiago Machado;K. B. Costa;F. Toledo;B. Dias;A. Albuquerque
从巴西电流的古海洋重建是稀缺的，缺乏所需的时间分辨率，以适当地代表其在最后一次冰期-间冰期循环的关键时期的变化。在这里，我们提出了第一个高时间分辨率的多代理重建的巴西电流在24° S覆盖过去185 ka。在末次冰期和倒数第二次冰期，我们的Mg/Ca衍生的海表温度（SST）记录显示，在约100 ℃时有一个强烈的冷却。47、你156 ka，其次是一个变暖的趋势，从晚海洋同位素阶段（MIS）3到MIS 1和晚MIS 6到MIS 5e。重要的是，巴西海流在大约1000年的低SST之后不间断地向终端I（II）变暖。47、你156 ka，在末次盛冰期或倒数第二次盛冰期没有SST极小值。MIS 3晚期和MIS 6晚期的强降温和升温趋势可能与有利的水汽结构有关。然而，这一机制不足以维持末次冰期和倒数第二次冰期其余时间观察到的变暖。我们建议，在大西洋纬向翻转环流（AMOC）的变化，如文献中所述，从“暖”到“冷模式”的MIS 2和MIS 6是负责在南大西洋西部的亚热带温暖的沃茨的积累，防止SST最小值在该地区的最后一次和倒数第二次冰期最大。底栖δ 13 C的变化证实，AMOC模式的根本改变可能触发了热量积累。我们的数据还显示，SST和表面盐度在末次冰期下降（MIS 4）突然增加，表明西部分的副热带环流可能充当了热盐水库，而高纬度气候过渡到冰川背景。我们的研究结果意味着，AMOC“冷模式”诱导热储存在亚热带西南大西洋，正因为如此，最后两个区域SST极小值发生的相位与高纬度的冰川极大值。
Paleoceanographic reconstructions from the Brazil Current are scarce and lack the required temporal resolution to appropriately represent its variability during key periods of the last glacial–interglacial cycles. Here, we present the first high-temporal resolution multiproxy reconstruction of the Brazil Current at 24° S covering the last 185 ka. During the last and penultimate glacial periods, our Mg/Ca-derived sea surface temperature (SST) record shows a strong cooling at ca. 47 and ca. 156 ka, respectively, that is followed by a warming trend from late-Marine Isotope Stage (MIS) 3 to MIS 1 and from late-MIS 6 to MIS5e, respectively. Importantly, the Brazil Current warmed uninterruptedly towards Termination I (II) after the low SST at ca. 47 and ca. 156 ka, with no SST minima during the Last Glacial Maximum or penultimate glacial maximum. The reason for the strong cooling and the warming trend during late-MIS 3 and late-MIS 6 could reside in the favorable obliquity configuration. However, this mechanism is not sufficient to sustain the warming observed for the rest of the last and penultimate glacial periods. We propose that the change in the Atlantic meridional overturning circulation (AMOC), as described in the literature, from a “warm” to a “cold mode” for MIS 2 and MIS 6 is responsible for the accumulation of warm waters in the subtropical western South Atlantic, preventing SST minima during the last and penultimate glacial maxima in the region. Change in benthic δ 13 C corroborates that a fundamental modification in the AMOC mode might have triggered the heat accumulation. Our data also show a sudden increase in SST and surface salinity during the last glacial descent (MIS 4), indicating that the western portion of the subtropical gyres may have acted as a heat and salt reservoir, while higher latitude climates transited to a glacial background. Our findings imply that the AMOC “cold mode” induces heat storage in the subtropical western South Atlantic and, because of that, the last two regional SST minima occurred out-of-phase with the glacial maxima of higher latitudes.