西北冰洋北风脊氧同位素5期以来的水体结构变化:来自有孔虫组合及其氧碳同位素的证据

WATER COLUMN STRUCTURE CHANGES ON THE NORTHWIND RIDGE,WESTERN ARCTIC OCEAN SINCE THE MARINE ISOTOPE STAGE 5:EVIDENCES FROM FORAMINIFERAL ASSEMBLAGES AND THEIR OXYGEN AND CARBON ISOTOPES

通过分析采集自北风脊的ARC3-P37岩心中有孔虫组合和浮游有孔虫氧碳同位素的变化,旨在反映深海氧同位素(MIS)5期以来西北冰洋水团和洋流系统对气候变化的响应。ARC3-P37中有孔虫丰度的大量增加可能反映了北太平洋水向西北冰洋的输入。有孔虫组合中浮游有孔虫Neogloboquadrina pachyderma(sin.)(Nps)占90%以上。底栖有孔虫组合以深水种Cibicidoides wuellerstorfi和Oridorsalis umbonatus为主,反映了主要受北极深层水和底层水影响的沉积环境,冷期大西洋水种Cassidulina neoteretis的出现反映了中层水下沉。Nps-δ13 C总体来说在暖期较重,反映较高生产力和海汽交换。而Nps-δ18 O受其生活习性迁移、水温变化、盐跃层深度变化、融冰作用的影响复杂多变,总体在冷期偏重,反映海冰环境,但在受融冰影响阶段反映为轻值。在MIS3期褐色层B2b之上,MIS1和MIS3期的Nps-δ18 O受到海水变暖和融冰水影响偏轻;而在B2b及其下部,暖期Nps-δ18 O偏重可能反映了盐跃层变浅和Nps生活习性向深部迁移。

Foraminifera assemblages and planktonic foraminiferal stable oxygen and carbon isotopes have been investigated for the core ARC3-P37,retrieved from the Northwind Ridge,Western Arctic Ocean,in order to decipher the water column structure and circulation changes in response to climate variations.The abrupt increase in foraminiferal abundance may indicate warm intervals with warm Pacific inflow to the Western Arctic Ocean.Planktonic species Neogloboquadrina pachyderma（sin.）（Nps）dominate the foraminiferal assemblage by over 90%.Benthic assemblage mainly comprises of deep water dwellers Cibicidoides wuellerstorfi and Oridorsalis umbonatus.The occurrence of Atlantic species Cassidulina neoteretis indicates the deepening of Arctic intermediate water.Nps-δ13C is generally heavy during warm intervals,reflecting good ventilation and high productivity.Nps-δ18 O variation is complicated and affected by the habitat of the species,water temperature,halocline depth,and meltwater etc.,generally showing heavy values during cold periods,while light values corresponding to meltwater input.Above the brown layer B2 bin MIS 3,light Nps-δ18 O is affected by warm sea water and meltwater discharge;while below B2 b,the heavy Nps-δ18 O during warm intervals may suggest shallowing of the halocline and the migration of Nps habitat to deeper layers.