Evolution Of Glaciomarine Environment And Paleoproductivity Since 34 Ka BP In The Scotia Sea,Antarctica

History of glaciomarine environment and paleoproductivity since 34 ka BP in the Scotia Sea,Antarctica were discussed based on chronological analyses of grain size,elemental geochemistry,biogenic silica,organic nitrogen and nitrogen isotopes in Core DC-11.The results show that:Based on the proxies such as the weight percentage of > 63?m grains,8 obvious ice-rafted debris events?IRD?and ice sheet instabilities were identified,most of which happened during warm periods.Among them,these two IRD events in the last glacial period are relatively small in magnitude while the events durng the Last Deglaciation are large in magnitude.The IRD events are frequent in Holocene.Climate and sea surface temperature have a significant impact on ice-rafted debris deposition in study area.The sortable silt,sorting coefficient and end-element analysis suggested that the silt in sediments of Core DC-11 is complicated,which is not only affected by ice raft debris,but also reflects the changes in bottom current in the local time windows.During 18.4?17.6 ka BP and 12.5?10.5 ka BP,the better sorting and consistent increases in the average size and content of the sortable silt indicate that the bottom current is enhanced during these periods.Since 34 ka BP,changes in BSiO₂ and )N_org contents are basically consistent with the Antarctica temperature,being higher in warm times.?¹⁵N_org ratios are coincident with the Antarctica 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 Antarctica Cold Reversal?ACR?is prominent in the study area.We suggest sea ice play an important role in correlations between the climate,nutrients and paleoproductivity.The increase of sea ice and the related stratification of surface waters during the glacial or cold periods caused reduced upwelling of deep waters and their dissolved nutrients to the surface ocean,and then resulted in enhanced nitrate utilization and decreased 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 Sub Antarctica Zone.