西北冰洋加拿大海盆MIS 8期以来的物源变化及其指示的北极冰盖和洋流的演化

SEDIMENT PROVENANCE VARIATIONS IN THE CANADA BASIN,WESTERN ARCTIC OCEAN SINCE MIS8:IMPLICATIONS ON ARCTIC ICE SHEET AND CIRCULATION CHANGES

基于对中国第七次北极考察在西北冰洋获得的ARC7-LIC岩芯上部1 m(加拿大海盆近阿尔法脊一侧)自MIS 8期(约300 ka)以来的粘土矿物和全样Sr-Nd-Pb同位素的分析,判断北冰洋中心沉积物源的变化及其所反映的冰盖和表层洋流的演化。结果显示:在MIS8、MIS5.4、MIS5.1、MIS3期中期冰筏事件以及末次冰消期,北美劳伦冰盖生长规模较大,研究区域的沉积被北美物源主导;相对地,MIS6、MIS4期的沉积由西伯利亚物源-穿极流模式主导,反映了欧亚大陆冰盖的大规模发育。同时,研究区域在MIS7、MIS5期的间冰期/间冰阶的沉积也与MIS3、MIS1期的沉积有所区别。MIS7、MIS5期的间冰期/间冰阶表现为西伯利亚物源以及穿极流控制下的沉积,而MIS3期和全新世则表现为北美物源以及波弗特环流作用下的沉积特征,这一差异说明中-晚第四纪间冰阶段北冰洋表层洋流的位置在晚更新世前后发生了变迁。

The advance and retreat of ice sheets around the Arctic Ocean during the Pleistocene drive the global climate variations through the glacial-interglacial cycles.However,detailed ice sheet development,and related Arctic Ocean circulation changes are poorly resolved due to the lack of stratigraphically well-constrained high resolution record.In this study,sediment provenance proxies including clay mineral composition and Sr-Nd-Pb radiogenic isotopes were analyzed from the upper section(1 m)of core ARC7-LIC(82°49’37″N,159°08’51″W;3018 m water depth),retrieved during the 7th Chinese National Arctic Research Expedition from the Canada Basin(off Alpha Ridge),western Arctic Ocean,in order to reveal the changes in the Arctic glaciation and surface ocean circulation since Marine Isotope Stage(MIS)8.The results show sediment provenances shifts at glacial-interglacial and stadialinterstadial time scales,indicating different configurations of Arctic ice sheets and circulation patterns over the last ca.300 ka in the Canada Basin.Strong influences of North American provenance were in MIS8,MIS5.4,MIS5.1,intra-MIS3 ice discharge events,and the last deglaciation,suggesting Laurentide Ice Sheet discharge during these periods.In comparison,the Eurasian provenance increases significantly during MIS6 and MIS4,indicating a dominance of a Transpolar Drift delivery and remarkable Ice Sheet enlargement on the Eurasian continent.Our data also suggests a major Siberian provenance and a Transpolar Drift input during interglacial/interstadial periods of MIS7 and MIS5,which is different from MIS3,MIS1 and the modern surface ocean circulation pattern in the Arctic Ocean.