白令海盆17ka以来的古海洋与古气候记录

PALEOCEANOGRAPHIC AND PALEOCLIMATIC RECORDS IN THE BERING BASIN OVER THE LAST 17 KA

通过白令海盆08BR02钻孔(57°0.06'N,174°29.97'E,水深3 805 m)的AMS14C测年数据、颜色反射率b*与NGRIP(North Greenland Ice Core Project)氧同位素曲线及白令海4个钻孔颜色反射率b*记录作对比,建立该孔的地层年代框架,顶、底部沉积物年龄分别为4.2 ka和17.0 ka。该孔自17 ka以来,IRD(ice-rafted detritus:冰筏碎屑)、粒度的砂组分以及敏感组分中的33—63μm组分百分含量在全球性冷事件H1(Heinrich event 1)、B/A(Blling/Allerd)中期和YD(Younger Dryas)期间明显增加。IRD和有孔虫丰度在H1、B/A和YD期间同步增加,可能反映海冰融化为表层水提供营养物质,促使表层钙质生产力勃发并将有机质进一步输送至海底,为底栖生物提供营养物质。

Investigations of the terrigenous and biogenic fractions have been performed on core 08BR02, which was collected from the Bering Basin, North Pacific Ocean, during the third Chinese National Arctic Expedition. The depth-age model for this core is based on age control points from AMS 14C dating of organic carbon and planktonic foraminifera, and correlation of the color b ＊ in this core with the NGRIP δ18O curve and color b ＊ of four sediment cores in the North Pacific Ocean and the Bering Sea. The sea ice extension history in the Bering Basin over the last 17 ka is reconstructed from the ice-rafted detritus （IRD）, the sand component and the sensitive grain size component （33--63 um in size）, which were carried by sea ice and icebergs, and increased during the H1, mid-B/A and YD periods. The IRD and the foraminiferal abundance in core 08BR02 increased simultaneously during the H1, mid-B/A and YD periods, indicating that input of meltwater enhanced the surface water nutrients, which then promoted blooms of planktonic foraminifera. The surface organic material that was deposited on the sea bottom provided nutrients for benthic foraminifera.