Marine ice-rafted debris records and age determinations along the northern Eurasian margin

Ice-rafted debris (IRD) (>2 mm), input in eight sediment cores along the Eurasian continental margin (Arctic Ocean), have been studied over the last two glacial/interglacial cycles. Together with the revised chronologies and new micropaleontological data of two cores from the northern Barents Sea (PS2138) and northeastern Kara Sea (PS2741) spanning Marine Isotope Stages (MIS) 6 to 1, the IRD data give new insights into the glacial history of northern Eurasian ice-sheets over the last 150 ka. The chronologies of the cores are based on stable isotope records, AMS 14C datings, paleomagnetic and biostratigraphic data.
Extensive episodes of northern Barents Sea ice-sheet growth, probably to the shelf edge, occurred during the late Weichselian (MIS 2) and the Saalian (MIS 6). Major IRD discharge at the MIS 4/3-transition hints to another severe glaciation, probably onto the outer shelf, during MIS 4. IRD-based instabilities of the marine-based ice margin along the northern Barents Sea between MIS 4 and 2 are similar in timing with North Atlantic Heinrich events and Nordic Seas IRD events, suggesting similar atmospheric cooling over a broad region or linkage of ice-sheet fluctuations through small sea-level events.
In the relatively low-precipitation areas of eastern Eurasia, IRD peak values during Termination II and MIS 4/3-transition suggest a Kara Sea ice-sheet advance onto the outer shelf, probably to the shelf edge, during glacial MIS 6 and 4. This suggests that during the initial cooling following the interglacials MIS 5, and possibly MIS 7, the combined effect of sustained inflow of Atlantic water into the Arctic Ocean and penetration of moisture-bearing cyclones into easterly direction supported major ice build-up during Saalian (MIS 6) and Mid-Weichselian (MIS 4) glaciation. IRD peak values in MIS 5 indicate at least two advances of the Severnaya Semlya ice-sheet to the coast line during the Early Weichselian. In contrast, a distinct Kara Sea ice advance during the Late Weichselian (MIS 2) is not documented by the IRD records along the northeastern Kara Sea margin.

针对北冰洋欧亚大陆边缘的8个沉积物岩芯中的>2 mm冰筏碎屑（Ice-rafted debris, IRD），研究人员已针对过去两个冰期-间冰期旋回开展了系统分析。结合巴伦支海北部（PS2138）与喀拉海东北部（PS2741）两个覆盖海洋同位素阶段（Marine Isotope Stages, MIS）6至1的岩芯的校正年代框架与新获取的微古生物数据，这套IRD数据为过去150 ka以来欧亚北部冰盖的冰期历史提供了全新认知。该批岩芯的年代框架基于稳定同位素记录、加速器质谱14C测年（AMS 14C datings）、古地磁与生物地层数据构建。

巴伦支海北部冰盖的大规模扩张（可能推进至陆架边缘）发生于晚威斯康星冰期（MIS 2）与萨勒冰期（MIS 6）。在MIS 4/3转换期出现的大规模IRD释放事件，指示了MIS 4时期又一次波及外陆架的严重冰川作用。巴伦支海北部海域在MIS 4至2期间的海基冰缘基于IRD识别出的不稳定性事件，其发生时间与北大西洋海因里希事件、北欧海IRD事件高度吻合，这表明该区域曾经历大范围同步大气降温，或是冰盖波动通过小型海平面事件实现了区域联动。

在欧亚大陆东部降水相对匮乏的区域，冰期终止II与MIS 4/3转换期出现的IRD峰值，表明在MIS 6与MIS 4冰期阶段，喀拉海冰盖曾推进至外陆架，甚至可能抵达陆架边缘。这一结果说明，在间冰期MIS 5（或还包括MIS 7）后的初始降温阶段，大西洋水持续注入北冰洋与携带水汽的气旋向东渗透的共同作用，支撑了萨勒冰期（MIS 6）与中威斯康星冰期（MIS 4）的大规模冰体堆积。MIS 5时期的IRD峰值则表明，早威斯康星冰期期间，谢韦尔纳亚谢姆利亚冰盖（Severnaya Semlya ice-sheet）至少两次推进至海岸线附近。与之形成对比的是，喀拉海东北部边缘的IRD记录并未显示晚威斯康星冰期（MIS 2）存在显著的喀拉海冰进事件。