Southern Hemisphere mid-latitude westerlies contribute to the ventilation of the deep Southern Ocean(SO),and drive changes in atmospheric carbon dioxide(CO2) and the global climate.As the westerlies control directly oceanic fronts,the movement of the subtropical front(STF) reflects the westerlies migration.Thus it is important to understand the relationships between STF movement and the weaterlies,ventilation of the deep SO,ice volume and atmospheric CO2.To this end,we use two new high-resolution records from early Marine Isotope Stage(MIS) 20(～800 ka) of sea surface temperature(SST) based on U k' 37 paleo-thermometer and benthic oxygen isotope(δ 18OB) at Ocean Drilling Program(ODP) Site 1170B in the southern Tasman Sea(STS),to construct linkages between the marine records and atmospheric proxies from Antarctic ice-cores.During the last 800 ka,the average SST(10.2℃) at Site 1170B is 1.8℃ lower than today(annual average 12℃).The highest average SST of 11.6℃ occurred during MIS 1,and the lowest average SST of 7.8℃ occurred during MIS 2.The warmest and coldest records of 14.7℃ and 6.2℃ occurred in the MIS 5 and MIS 2,respectively.In the glacial-interglacial cycles of the last 800 ka,variability of reconstructed SST shows that the STF moved northward or southward more than 3° of latitude compared with its present location.In the warmest stage MIS 5,the STF shifted to its southernmost location of ～49°S.In contrast,in the coldest stage MIS 2,the STF moved to its northernmost location of ～43°S.In response to orbital cycles,the westerlies movement led ice volume and atmospheric CO2 changes,but it was in phase with change in Antarctic atmospheric temperature.Ice volume only preceded atmospheric CO2 only a little at the 23-ka precession band,lagged the atmospheric CO2 at the 100-ka eccentricity band,and was in phase with atmospheric CO2 at the 40-ka obliquity band.
LI WenBaoWANG RuJianXIANG FeiDING XiaoHuiZHAO MeiXun
The late Quaternary ice rafted detritus (IRD) events in the Chukchi Basin, western Arctic Ocean are indications of the provenance of the coarser detritus and ice export events, and also document the evolutionary histories of Beaufort Gyre and the North American Ice Sheet (NAIS). The sediment of core M03 from the Chukchi Basin was selected to study the regional response to the ice export events and the NAIS variability. The stratigraphic framework of M03 was established by a combination of lithological features and downcore color change cycles, AMS14C dating with foraminifera abundance and IRD events. The core was also compared with the adjacent core NWR 5 from the Northwind Ridge area. The core extends back to Marine Isotope Stage (MIS) 7. A sedimentary hiatus of 10―20 ka might occur between 16 to 20 cm core depth. Seven IRD events are distinguished from the studied core and are presented during the early MIS 1, MIS 3, MIS 5 and late MIS 7. These IRD are transported by sea ice and icebergs, which were exported to the Beaufort Sea from the M'Clure Strait Ice Stream, Canadian Arctic Archipelago, and brought to the Chukchi Basin by the Beaufort Gyre.
