3.4万年以来南极斯科舍海古生产力演变及其环境制约

本文通过对南极斯科舍海东南部DC-11岩芯生物硅、有机氮、TFe₂O₃与有机氮同位素的年代学分析，重建了该海区3.4万年以来古生产力与环境演变历史。研究结果表明，生物硅、有机氮含量与南极温度变化基本一致，暖期高、冷期低；有机氮同位素值与南大洋海冰变化相吻合，暖期小、冷期大，冷期硝酸盐利用率大于暖期。从末次冰期、末次冰消期至全新世，研究区古生产力与环境变化显著，南极冷倒转等千年尺度的变化明显；海冰在气候、营养盐与古生产力之间起着重要的关联作用。冰期或冷期海冰的加强导致表层水层化加强，深层水及其营养盐的上涌减弱，表层海洋硝酸盐等相对匮乏，生产力降低。研究区现代与全新世铁供应充足，在风尘盛行的末次冰期和冰消期呈过剩状态，明显不同于亚南极。

Paleoproductivity and its environmental constraints in the Scotia Sea,Antarctica since 34 ka BP

Paleoproductivity and environmental evolution since 34 ka BP in the southeastern Scotia Sea,Antarctica were reconstructed by the chronological analyses of biogenic opal(BSiO2),organic nitrogen(Norg),TFe₂O₃ and organic nitrogen isotopes(15^δN_org)in Core DC-11.Changes in BSiO₂and Norg contents are basically consistent with the Antarctic temperature,being higher in warm times.δ15Norg is coincident with the Antarctic sea ice,being greater and reflecting enhanced nitrate utilization in surface water during cold periods.From Last Glacial,Last Deglaciation to Holocene,paleoproductivity and environment changed significantly,and the millennial variability such as the Antarctic Cold Reversal(ACR)is prominent in the study area.Sea ice plays an important role in correlations between the climate,nutrients and paleoproductivity.The increase of sea ice during the glacial or cold periods caused stronger stratification of surface waters,weaker upwelling of deep waters and their dissolved nutrients to the surface ocean,and then resulted in enhanced nitrate utilization and lower paleoproductivity in surface water.Iron supply in the study area is sufficient in present-day and Holocene while it is excessive during Last Glacial and Last Deglaciation due to more developed dust,which is obviously different from that in the Subantarctic Zone.