RETREAT PROCESS OF ROSS ICE SHELF AND HYDRODYNAMIC CHANGES ON NORTHWESTERN ROSS CONTINENTAL SHELF SINCE THE LAST GLACIAL

The retreat process of Ross Ice Shelf (RIS) has important impact on the changes in global climate and ocean circulation. Analysis of Ice Rafted Debris (IRD) and grain size has been performed for the core ANT31-JB06 to reconstruct the process of RIS deglaciation since the last glacial. The core was retrieved from the JOIDES Trough on the northwest Ross Sea continental shelf during the 31th Chinese Antarctic Expedition. AMS ¹⁴C based chronology suggests a complete depositional sequence of the past 36.6 ka for the studied core. End Member Modelling of the grain size distribution suggests particle mode sizes of 15.1 μm and 18.9 μm representing weak and strong hydrodynamic environment, respectively, while particle mode sizes of 63.4 μm and 234.1 μm representing transportation by sea ice and iceberg, respectively. During the Last Glacial, RIS did not ground at our core site, while the RIS was at its maximum extent at 27~21 ka. The deglacial retreat of the RIS from the JIODES Trough was at about 21 ka. A major disintergration and retreat of the RIS marked the AIM1 warm interval (17~14 ka), followed by a slow down or cease of retreat during the Antarctica Cold Reversal (ACR) (14~12 ka). A second major retreat of the RIS occurred during the early-mid Holocene. The RIS stabilized after about 5 ka. Strong bottom currents characterized the cold intervals while weaker during the warm intervals, probably ascribed to stronger sea ice formation and/or bottom water production during cold intervals.