California Current System During the Last Six Centuries: Response to Abrupt Climatic Changes

圣巴巴拉盆地的各种沉积物是温带-亚北极和亚热带动植物的独特记录器，它通过厌氧沉积保存了年度信号。地表水生产力和海底养护的波动极大地放大了气候变化的影响。例如，在强厄尔尼诺事件期间引入亚热带生物群的同时，光带的生物生产力下降，而其他情况下缺氧的底层水的含氧量增加。在这个跨学科的研究项目中，首先将对加利福尼亚州圣巴巴拉盆地的沉积物岩心进行物理和化学研究，以确定过去600年内气候变化迅速或剧烈波动的时期。然后将详细研究这些突然变化，以确定硅藻植物群和有孔虫动物群的变化，包括浮游和底栖动物的变化，以及地球化学和同位素参数的变化。由此产生的多学科时间序列将根据加州洋流海洋条件的变化进行解释，使用先前计算出的校准。结果将与来自北美和北半球其他地区的树木年轮和冰层记录的信息进行比较。其目的是评估过去不寻常事件的频率，它们在加州海流中的表现，就其多样的记录而言，以及与其他地方气候变化的遥相关(如果有的话)。

Varved sediment in the Santa Barbara Basin is a unique recorder of temperate-subarctic and subtropical flora and fauna which preserves an annual signal through anaerobic deposition. Effects of climatic change are greatly magnified by fluctuations in the productivity of surface waters and of preservation at the seafloor. For example, the introduction of subtropic biota during strong El Nino events coincides with decreased bioproductivity in the photic zone and with increases oxygenation of the otherwise anoxic bottom waters. In this interdisciplinary research project sediment cores from Santa Barbara Basin off California will first be studied by physical and chemical means to identify periods, within the last 600 years, when climate changed rapidly of fluctuated strongly. These abrupt changes will then be scrutinized in detail, for changes in diatom flora and foraminiferal fauna, both planktonic and benthic, and for shifts in geochemical and isotopic parameters. The resulting multidisciplinary time series are to be interpreted in terms of changes in the oceanographic conditions of the California Current, using calibrations worked out previously. The results are to be compared with information from tree rings and ice records from North America and other regions of the Northern hemisphere. The aim is to assess the frequency of unusual events in the past, their expression in the California Current as far as it can be read from its varved record, and the teleconnections, if any, with climatic changes elsewhere.