A multi-proxy investigation of sediment core GeoB7165-1 and AMS 14C dating points from sediment cores off Conceptión (~ 36°S)

A high-resolution sea surface temperature and paleoproductivity reconstruction on a sedimentary record collected at 36°S off central-south Chile (GeoB 7165-1, 36°33'S, 73°40'W, 797 m water depth, core length 750 cm) indicates that paleoceanographic conditions changed abruptly between 18 and 17 ka. Comparative analysis of several cores along the Chilean continental margin (30°-41°S) suggests that the onset and the pattern of deglacial warming was not uniform off central-south Chile due to the progressive southward migration of the Southern Westerlies and local variations in upwelling. Marine productivity augmented rather abruptly at 13-14 ka, well after the oceanographic changes.We suggest that the late deglacial increase in paleoproductivity off central-south Chile reflects the onset of an active upwelling system bringing nutrient-rich, oxygen-poor Equatorial SubsurfaceWater to the euphotic zone, and a relatively higher nutrient load of the Antarctic Circumpolar Current. During the Last Glacial Maximum, when the Southern Westerlies were located further north, productivity off central-south Chile, in contrast to off northern Chile, was reduced due to direct onshore-blowing winds that prevented coastal upwelling and export production.

对智利中南部外海36°S海域采集的沉积岩芯（GeoB 7165-1，站位坐标36°33'S、73°40'W，水深797米，岩芯总长750厘米）所获沉积记录开展的高分辨率海表温度（sea surface temperature）与古生产力（paleoproductivity）重建结果显示，古海洋环境在18~17 ka期间发生了突变。对智利大陆边缘（30°~41°S）多根岩芯的对比分析表明，受南西风带（Southern Westerlies）持续向南迁移以及局地上升流变化的影响，智利中南部外海的冰消期变暖起始过程与演化模式并不均一。海洋生产力在13~14 ka期间出现显著跃升，这一时间远晚于该区域海洋环境的突变时段。我们认为，智利中南部外海冰消期后期古生产力的提升，反映了活跃上升流系统的启动——该系统将富含营养盐且溶解氧匮乏的赤道次表层水（Equatorial Subsurface Water）输送至真光层（euphotic zone），同时南极绕极流（Antarctic Circumpolar Current）的营养盐负荷也相对更高。在末次冰盛期（Last Glacial Maximum），南西风带位置更偏北，与智利北部外海的情况相反，智利中南部外海的生产力因盛行向岸风抑制了沿岸上升流与生源物质输出而出现降低。