楚科奇海中全新世以来的硅藻记录及古环境意义

DIATOMS AS INDICATORS OF THE MID-HOLOCENE ENVIRONMENTAL CHANGES IN THE CHUKCHI SEA

对楚科奇海中部沉积物岩芯中的硅藻进行鉴定,共发现52属97种。运用聚类分析方法可将该岩芯分为3个硅藻带。5-3.5 cal ka BP期间海冰硅藻含量较高但有明显的下降趋势,硅藻丰度不断上升并达到峰值,表明此期间太平洋暖水流入楚科奇海加速了海冰退缩,促进了楚科奇海中部海域海洋生产力的发展。淡水种含量在此阶段有所增加,表明阿拉斯加沿岸流对楚科奇海中部海域海洋环境的影响增强。3.5-1.3 cal ka BP时期硅藻丰度持续降低表明楚科奇海浮游生物生产力减弱,这与太平洋水流入减少、海冰覆盖增加有一定的关联。而来自于阿拉斯加沿岸流携带的淡水硅藻含量较低,表明此时阿拉斯加沿岸流势力减弱。1.3-0 cal ka BP期间,海冰硅藻含量波动上升,硅藻丰度处于较低水平,表明全新世晚期白令海入流减弱,海冰覆盖范围有所扩大。楚科奇海中部中全新世以来的沉积硅藻记录表明,太平洋暖水流入的强弱变化与研究区的海冰覆盖情况,共同控制着研究区的海洋生产力变化。

Total 97 species and varieties of diatoms from 52 genera were identified from Core R09 in the central Chukchi Sea.The cluster analysis result showed that the content of sea-ice diatoms was high during 5-3.5 cal ka BP,with an obvious decrease,but the total abundance of diatoms kept rising and reached the peak,indicating that the inflow of Pacific warm water into the Chukchi Sea accelerated the retreat of sea ice and promoted the development of Marine productivity in the central Chukchi Sea.The freshwater species content increased during this period,indicating that the influence of the Alaskan coastal current on the Marine environment in the central Chukchi Sea was enhanced.The continuous decrease of diatom abundance during 3.5-1.3 cal ka BP indicates that biological productivity was reduced,which was related to the decrease of Pacific warm water inflow and the increase of sea ice cover.At the same period,the content of freshwater diatoms carried by the Alaska coastal current was low,indicating that the Alaska coastal current was weakened.During 1.3-0 cal ka BP,the content of sea ice diatoms rose in fluctuation and diatoms abundance was at a low level,indicating that the Bering Sea inflow weakened and the coverage of sea ice expanded in the Late Holocene.The sedimentary diatoms recorded in the central Chukchi Sea since the Mid-Holocene show that the change of Pacific Ocean inflow and sea ice cover in the study area co-controlled the change of marine productivity.