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Pleistocene water cycle and eastern boundary current processes along the California continental margin

机译：加利福尼亚大陆边缘的更新世水循环和东部边界水流过程

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Coastal marine sediments contain mixtures of terrestrial and marine paleoclimate proxies that record how the coastal water cycle has behaved over long time frames. We explore a 600 kyr marine record from ODP Site 1018, located due west of Santa Cruz, California, to identify coastal wet and dry periods and to associate them with oceanographic processes. Wet periods in central California, identified by increased tree pollen relative to pollen from grasslands and scrublands, are found on every major deglaciation in the last 600 kyr. Sea surface temperature (SST) data were collected for the last two deglaciations. Wet periods are associated with a rapid rise in SST off central California. SST gradients along the California margin and changes in biogenic deposition show that wet periods in central California are associated with a weakening of the California Current and weakened coastal upwelling. High carbonate production suggests that there was significant curl-of-wind stress upwelling offshore. We propose that wet periods in central California are associated with a meteorological connection to the tropical Pacific and weakened southward flow in the California Current that shunted temperate Pacific water northward into the Alaska gyre. We do not observe evidence for a south-shifted westerly storm track at the last glacial maximum but find that wet periods are diachronous along the California margin. The wettest period around the Santa Barbara Basin peaked at 16 ka, preceding the wet peak in central and northern California by 4 kyr.
机译：沿海海洋沉积物包含陆地和海洋古气候代理的混合物，这些代理记录了沿海水循环长期以来的行为。我们从位于加利福尼亚州圣克鲁斯以西的ODP站点1018探索了600年的海洋记录，以识别沿海的干湿期并将其与海洋学过程联系起来。加利福尼亚中部的湿润时期被发现为相对于草地和灌丛的花粉而言，树木花粉相对增加，这是在过去600年来的每次主要冰消作用中发现的。收集了最后两次冰消的海面温度（SST）数据。湿润时期与加利福尼亚中部海域海温快速上升有关。沿着加利福尼亚边缘的海表温度梯度和生物成因的变化表明，加利福尼亚中部的湿润时期与加利福尼亚洋流减弱和沿海上升流减弱有关。较高的碳酸盐产量表明，海上有明显的风向弯曲应力。我们认为，加利福尼亚中部的湿润时期与与热带太平洋的气象联系有关，并且减弱了加利福尼亚洋流的向南流动，从而使温带太平洋水向北分流到阿拉斯加回旋处。我们没有观察到在最后一次冰川最大时出现南风西风风暴轨迹的证据，但发现沿加利福尼亚边缘的湿润时期是历时的。圣塔芭芭拉盆地周围最湿的时期达到16 ka，比加利福尼亚中部和北部的湿峰高出4年。

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