Late Holocene multi-decadal to centennial scale oceanic variability on the eastern Canadian shelf linked to North Atlantic climatic changes

在过去的3000年里，北大西洋地区发生了一系列明显的千年到百年尺度的海洋和气候振荡。越来越多的证据表明，北冰洋通过东格陵兰洋流路线的可变淡水平流和格陵兰冰盖的当地融水供应与这些振荡有关，并导致地表水和次表层水条件的广泛脱钩。特别是在亚极北大西洋，这种脱钩是沿着亚极环流的北/西北边界流，即东格陵兰流和西格陵兰流记录的。然而，关于晚全新世通过北冰洋第二条主要淡水外流路线--加拿大西部北极群岛的淡水平流，人们对此知之甚少，这对拉布拉多海流的性质有很大影响。拉布拉多海流与东、西格陵兰海流一起影响亚极地环流，从而调节北大西洋北部的热量平流，从而影响北半球的气候条件。由于有关通过加拿大北极群岛/拉布拉多海流路线的淡水外流变化的信息有限，我们对北大西洋千年至百年尺度气候变异性的理解受到限制。拟议的多代理研究结合了定性(有孔虫组合)和定量(稳定同位素和微量元素研究，烯酮)，首次以高分辨率重建了加拿大东部陆架的海洋沉积物岩心、地表(淡水)和地下水条件。在一项初步研究中获得的放射性碳测年和放射性核素测量证明，这些岩芯是在2015年MSM45和46航次期间收集的，解决了晚全新世几十年到百年尺度的海洋和气候变化。拟议对从哈德逊海峡到圣劳伦斯湾的加拿大东部大陆架的地表水和次表层水性质进行多代理调查，将能够评估海洋变化与北大西洋次极区域在全新世晚期数十年至百年尺度气候变化之间的联系。

A series of distinct millennial to centennial scale oceanic and climatic oscillations occurred in the North Atlantic region during the last 3000 years. There is increasing evidence that variable freshwater advection from the Arctic Ocean via the East Greenland Current route and local meltwater supply from the Greenland Ice sheet is linked to these oscillations and caused a widespread decoupling of surface and subsurface water conditions. Particularly within the subpolar North Atlantic this decoupling is documented along the N/NW boundary currents of the Subpolar Gyre, i.e. the East Greenland Current, and West Greenland Current. However, little is known concerning the late Holocene freshwater advection via the second major Arctic Ocean freshwater outflow route, the western Canadian Arctic Archipelago, which strongly influences the Labrador Current properties. The Labrador Current, in turn, together with the East and West Greenland Current affects the Subpolar Gyre circulation, which regulates the heat advection into the northern North Atlantic and thus, northern hemisphere climatic conditions. As only limited information on freshwater outflow changes via the Canadian Arctic Archipelago/Labrador Current route is available, our understanding of millennial to centennial scale North Atlantic climate variability is constrained. The proposed multi-proxy study combining qualitative (foraminifer assemblages) and quantitative (stable isotope and trace element studies, alkenones) reconstructs for the first time, from marine sediment cores, surface (freshwater) and subsurface water conditions on the eastern Canadian shelf at a high resolution. Radiocarbon dates and radionuclide measurements, obtained during a pilot study, prove that these cores, collected in 2015 during the MSM45 and 46 cruises, resolve late Holocene oceanic and climatic changes at a multi-decadal to centennial scale. The proposed multi-proxy investigations of surface and subsurface water properties, spanning the eastern Canadian shelf from Hudson Strait to the Gulf of St. Lawrence, will allow assessing the link between oceanic changes, and the subpolar North Atlantic multi-decadal to centennial scale climate variability during the late Holocene.