全新世冲绳海槽北部表层海水温度和初级生产力对黑潮变迁的响应

在冲绳海槽北部B-3GC孔高分辨率地层年代框架的基础上,利用多种分子生物标志物和生源组分指标,重建了该地区全新世以来表层海水温度和生产力的变化历史.研究发现,U37K-表层海水温度和生产力的变化指示了全新世黑潮及对马暖流分支的变迁.10.6～7.3 ka BP期间,冲绳海槽北部主要受东海陆架冷水团影响,陆源物质输入量增加,初级生产力比较高,表层海水温度较低.7.3～4.6 ka BP期间,黑潮暖流对该区的影响迅速增强,表层海水快速增温,陆源物质输入减少,但是各种生产力指标显示出上升趋势,与该区上升流的出现和迅速发育有关.4.6～2.7 ka BP期间,即全新世普林虫低值事件(PME)期间,表层海水温度明显降低了0.8～1.4℃,陆源物质输入增加,初级生产力和各种生源组分的含量也达到较高水平,说明此时黑潮强度减弱,或者黑潮主流轴向太平洋方向发生偏移,该区再次受到陆架冲淡水的影响.2.7 ka BP以来,虽然黑潮暖流再次影响到该海区,但初级生产力和生源物质输出量继续大幅增高,可能与该地区上升流的持续发育有关.

Responses of Sea Surface Temperature and Productivity to the Changes of the Kuroshio Current in the Northern Okinawa Trough during the Holocene

Based upon a high resolution stratigraphic and chronologic framework of core B-3GC in the northern Okinawa Trough during the Holocene, multi-proxies, including a set of marine biomarkers, contents of total organic carbon, opal and CaCO₃, are used to reconstruct the past changes of sea surface temperature (SST) and productivity. Evident fluctuations of U^K′₃₇-SST and sea surface productivity records could indicate directly the variability of the Kuroshio-Tsushima Current. During 10.6~7.3 ka BP, when the northern Okinawa Trough was dominated by cold coastal water mass from the East China Sea, increasing terrigenous matter input enhanced the primary productivity, whereas the U^K′₃₇-SST remained lowering. During 7.3~4.6 ka BP, when the northern Okinawa Trough was abruptly influenced by the Kuroshio Current, the U^K′₃₇-SST increased and terrigenous matter input decreased. Although the Kuroshio Current prevented the intrusion from the coastal waters, contents of biomarkers and biogenic components still continuously increased, which was probably caused by the strengthened upwelling in this region. During 4.6~2.7 ka BP (Pulleniatina Minimum Event, PME), the U^K′₃₇-SST recorded an evident cooling signal of 0.8~1.4℃, meanwhile, terrigenous matter input, productivity as well as biogenic components all greatly increased. All these changes suggest that the influence of the Kuroshio Current sharply weakened or its main axis may shift to the open Pacific Ocean in this interval. The northern Okinawa Trough was again affected by the coastal waters. During 2.7 ka BP to the present, the Kuroshio Current probably reentered this region, resulting in a warm SST condition. However, primary productivity and biogenic components drastically increased, which may be induced by the persistently enhanced upwelling in the northern Okinawa Trough.