Response of the northwestern Pacific upper water δ 13C to the last deglacial ventilation of the deep Southern Ocean

Abstract

The deglacial δ 13C minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad δ 13C minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of influence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054 from the KSR are well positioned to identify signals from the southern hemisphere in the northwestern Pacific. Planktonic foraminiferal tests from the upper 1030 cm of the core were subject to AMS 14C, carbon and oxygen isotopic measurements. A negative excursion was found to occur from about 20.0-6.0 ka BP in δ 13C records of both surface (Globigerinoides ruber) and subsurface (Pulleniatina obliquiloculata) dwellers, but the overall trends of the two curves have reversed since 26.5 ka BP. Moreover, the δ 13C record of G. ruber (the surface dweller) shows a robust link to the record of atmospheric CO 2, and its changes precede the records of P. obliquiloculata (the subsurface dweller). According to the hydrologic conditions, the broad δ 13C minimum event recorded in the KSR is also a response to the increasing ventilation of the deep Southern Ocean around Antarctica during the last deglaciation. The inconsistency between the records of the surface and subsurface dwellers was possibly caused by the ways that the low δ 13C signal was transmitted. Subsurface water primarily received the low δ 13C signal from the Antarctic Intermediate Water (AAIW), whereas the surface water was probably mainly impacted by atmospheric CO 2 in the KSR. The records from the KSR confirm the deduction that the broad δ 13C minimum event in the Okinawa Trough was due to the impact of tropical Pacific surface water during the last deglaciation, and suggest that signals from the southern high latitudes also can be delivered to the northern middle latitudes. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.