罗斯海西北陆架(JOIDES海槽)末次冰期以来冰架消融过程及水动力变化

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

罗斯冰架的消融过程对全球气候和大洋环流的变化都有重要影响。通过分析罗斯海西北陆架上中国第31次南极考察所采集的ANT31-JB06岩心重建末次冰期以来罗斯冰架的消融历史。通过AMS 14 C测年,建立了该岩心的地层年代框架,其沉积物被划分为末次冰期（36.6ka）以来到全新世的沉积序列,并对该岩心进行了粗组分含量分析、粒度组成及其端元模拟的综合研究。该岩心的粒度端元分析结果显示,峰态中值为15.1和18.9μm的组分端元的变化可分别代表弱和强水动力环境,而峰态中值为63.4和234.1μm的组分端元的变化可分别代表海冰和冰山搬运等沉积动力的变化。末次冰期罗斯冰架在研究站位并未触底,在27～21ka左右增长到最大位置,可能已经到达该岩心所在的位置。罗斯冰架在21ka左右开始退离JOIDES海槽,在AIM 1暖期（17～14ka）大规模崩塌消退;而在南极冷反转ACR时期（14～12ka）罗斯冰架消退缓慢;ACR之后冰架继续崩塌直到全新世中期,在5ka左右罗斯冰架基本达到稳定状态。该处水动力在冷气候时期较强,在暖气候时期较弱,可能是气候较冷时结冰过程形成的盐度较大的水下沉到底部促进了上下水体交换,使得沉积界面的水动力相对也比较强,沉降下来的颗粒相对偏粗。

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 31 th Chinese Antarctic Expedition.AMS 14 C based chronology suggests a complete depositional sequence of the past 36.6ka for the studied core.End Member Modelling of the grain size distribution suggests particle mode sizes of 15.1μm and 18.9μm representing weak and strong hydrodynamic environment,respectively,while particle mode sizes of 63.4μm and 234.1μm 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 27～21ka.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（17～14ka）,followed by a slow down or cease of retreat during the Antarctica Cold Reversal（ACR）（14～12ka）.A second major retreat of the RIS occurred during the early-mid Holocene.The RIS stabilized after about 5ka.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.