Interaction between warm Atlantic-sourced waters and the East Greenland Current in northern Denmark Strait (68°N) during the last 10 600 cal a BP

Changes in the Holocene interaction of the (i) cold/fresh East Greenland Current (EGC) and (ii) warm/saline Irminger Current (IC) in northern Denmark Strait have been reconstructed from benthic and planktic foraminifera assemblages, ice-rafted debris, grain-size analyses and quantitative X-ray diffraction. During the time from c. 10 600 to 8000 cal a BP, palaeoceanographic reconstructions reveal waning deglacial influence from the receding Greenland Ice Sheet and presence of a strong EGC caused low surface water productivity. From c. 8000 cal a BP, a predominant influence of Atlantic-sourced IC waters on subsurface water conditions became established in northern Denmark Strait, which accompanied low surface water productivity. Relatively warm surface and subsurface water conditions, i.e. reduced EGC and strong IC influence, are found from c. 6500 to 4500 cal a BP, representing Holocene optimum-like conditions. A mid- to late Holocene EGC strengthening caused increased stratification and formation of a distinct halocline. However, we recognize millennial-scale periods of reduced stratification by an enhanced influence of Atlantic-sourced IC Water on surface water conditions: (i) at c. 2500–1400 cal a BP - the time of the Roman Warm Period and (ii) at c. 300 cal a BP - the later part of the Little Ice Age. These periods of oceanic warming probably relate to changes in the Subpolar Gyre dynamics that led to enhanced entrainment of Atlantic-sourced IC Water into northern Denmark Strait.

基于底栖与浮游有孔虫组合、冰筏碎屑、粒度分析及定量X射线衍射（quantitative X-ray diffraction）数据，研究重建了丹麦海峡北部全新世时期（i）冷淡型东格陵兰洋流（East Greenland Current, EGC）与（ii）暖盐型伊尔明厄洋流（Irminger Current, IC）的相互作用演化历史。
在约10600至8000校准距今年（cal a BP）时段，古海洋学重建结果显示，退缩的格陵兰冰盖（Greenland Ice Sheet）对研究区的冰消期影响逐渐减弱，且强盛的东格陵兰洋流导致表层水生产力低下。
自约8000校准距今年起，丹麦海峡北部次表层水状况开始主要受大西洋源伊尔明厄洋流水体影响，该时期表层水生产力同样偏低。
约6500至4500校准距今年时段，研究区表层与次表层水整体偏暖，即东格陵兰洋流影响减弱、伊尔明厄洋流影响增强，对应类似全新世适宜期的环境状态。
中晚全新世时期东格陵兰洋流增强，引发水体层化作用加剧并形成显著的盐跃层（halocline）。不过，研究识别出千年尺度的层化作用减弱时段，此时大西洋源伊尔明厄洋流对表层水的影响增强：其一为约2500至1400校准距今年——对应罗马暖期（Roman Warm Period）；其二为约300校准距今年——小冰期（Little Ice Age）后期。
这些海洋增温时段可能与副极地环流（Subpolar Gyre）动力变化相关，后者使得大西洋源伊尔明厄洋流更多卷挟进入丹麦海峡北部海域。