Ice-rafted debris, geochemistry and stable oxygen isotope record of sediment core MD99-2277

Sediment proxy records from a continuous, 1.5 million year long deep-sea sediment core from a site in the western Norwegian Sea were used to obtain new insights into the nature of palaeoceanographic change in the northern North Atlantic (Nordic seas) during the climatic shift of the Mid-Pleistocene Revolution (MPR). Red-green sediment colour and magnetic susceptibility records both reveal significant differences in their mean values when comparing the intervals older than 700 000 yr (700 ka) with those from the past 500 kyr. The timing and duration of these changes indicates that the MPR in the Nordic seas is characterised by a gradual transition lasting about 200 kyr. Together with further sedimentological evidence this suggests that the mid-Pleistocene climate shift was accompanied by a general change in ice-drift pattern. It is further proposed that prior to the onset of the major late Pleistocene glaciations in the Northern Hemisphere a significant proportion of the ice in the eastern Nordic seas originated from a southern provenance, whereas later it dominantly came from the surrounding landmasses.本研究利用挪威海西部海域某站位获取的连续150万年深海沉积岩芯的沉积物代用指标记录（sediment proxy records），为解析北大西洋北部（挪威海）在中更新世革命（Mid-Pleistocene Revolution, MPR）气候转型期间的古海洋学变化本质提供了全新认知。红-绿沉积物颜色与磁化率（magnetic susceptibility）记录均显示，对比70万年（700 ka）之前与过去50万年（kyr）的沉积段，二者的平均值存在显著差异。上述变化的发生时间与持续时长表明，挪威海区域的中更新世革命以一段持续约20万年的渐进式转型为核心特征。结合进一步的沉积学（sedimentological）证据，该结果暗示中更新世气候转型伴随了冰运模式的全局性转变。研究还提出，在北半球晚更新世大规模冰川作用（glaciations）启动前，挪威海东部的相当比例冰体源自南部物源区；而在此之后，冰体则主要来源于周边陆块。