Mid to late Holocene strengthening of the East Greenland Current linked to warm subsurface Atlantic water
Mid to late Holocene strengthening of the East Greenland Current linked to warm subsurface Atlantic water
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DOI：
10.1016/j.quascirev.2015.10.007
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发表时间：
2015-12
影响因子：
4
通讯作者：
K. Perner;M. Moros;J. Lloyd;E. Jansen;R. Stein
中科院分区：
文献类型：
--
作者：
K. Perner;M. Moros;J. Lloyd;E. Jansen;R. Stein
相对新鲜和寒冷的东格陵兰海流（EGC）将北极与副极地北大西洋连接起来。它的强度和对北大西洋淡水平衡的影响影响到拉布拉多海的副极地环流动力学和深层对流。加强淡水和海冰的扩张在北大西洋副极地的建议，以修改北大西洋电流内的向北的热输送。高分辨率的古海洋重建，南极和底栖有孔虫组合数据的基础上，从东格陵兰大陆架中部（福斯特湾）揭示了不同的百年到千年尺度的海洋变化，涉及到气候变化在全新世中期至晚期（最后c.6.3 ka BP）。我们的数据突出的冷却和清新的极地表面EGC沃茨，伴随着在地下大西洋沃茨，这是一个组合的冷却大西洋中层水（AIW）从北冰洋和返回大西洋电流（RAC）从西斯匹次卑尔根电流（WSC）变暖的间隔。全新世中期的热最佳条件一直持续到4.5 ka BP。一个薄/缺席的表面极地水层，低漂移/海冰发生和强大的贡献，再循环温暖的大西洋沃茨在次表层，建议在此期间相对较弱的EGC。随后，在1.4和4.5 ka BP之间，水柱变得分层良好的表面极地水层增厚和冷却，表明一个强大的EGC。这EGC加强平行增强的次表层冷却AIW的贡献，从北冰洋后。4.5 ka BP，达到高潮，从1.4到2.3 ka BP。这与北大西洋海流、伊明格海流和西格陵兰海流早期研究中发现的变暖相吻合。我们将这一时期寒冷的大西洋水的贡献增强与“罗马温暖期”的时间联系起来。所观察到的东格陵兰近海变暖，集中atc.1.8 ka BP，可能发生在响应的变化的相互作用，i）一个减弱的副极地环流; ii）增加向北的热平流在北大西洋电流，和iii）一个主要的积极的北大西洋和北极涛动模式，在罗马温暖期的时间盛行。
The relatively fresh and cold East Greenland Current (EGC) connects the Arctic with the subpolar North Atlantic Ocean. Its strength and influence on the freshwater balance in the North Atlantic affects both the Subpolar Gyre dynamics and deep convection in the Labrador Sea. Enhanced freshwater and sea-ice expansion in the subpolar North Atlantic is suggested to modify the northward heat transport within the North Atlantic Current. High-resolution palaeoceanographic reconstructions, based on planktic and benthic foraminifera assemblage data, from the central East Greenland shelf (Foster Bugt) reveal distinct centennial to millennial-scale oceanographic variability that relates to climatic changes during the mid to late Holocene (the lastc.6.3 ka BP). Our data highlight intervals of cooling and freshening of the polar surface EGC waters that accompany warming in the subsurface Atlantic waters, which are a combination of chilled Atlantic Intermediate Water (AIW) from the Arctic Ocean and of the Return Atlantic Current (RAC) from the West Spitsbergen Current (WSC). Mid Holocene thermal optimum conditions prevailed untilc.4.5 ka BP. A thin/absent surface Polar Water layer, low drift/sea-ice occurrence and strong contribution of recirculating warm Atlantic waters at the subsurface, suggest a relatively weak EGC during this period. Subsequently, between 1.4 and 4.5 ka BP, the water column became well stratified as the surface Polar Water layer thickened and cooled, indicating a strong EGC. This EGC strengthening parallelled enhanced subsurface chilled AIW contribution from the Arctic Ocean afterc.4.5 ka BP, which culminated from 1.4 to 2.3 ka BP. This coincides with warming identified in earlier work of the North Atlantic Current, the Irminger Current, and the West Greenland Current. We link the enhanced contribution of chilled Atlantic Water during this period to the time of the ‘Roman Warm Period’. The observed warming offshore East Greenland, centred atc.1.8 ka BP, likely occurred in response to changes in the interactions of i) a weakened Subpolar Gyre; ii) increased northward heat advection in the North Atlantic Current, and iii) a predominant positive North Atlantic and Arctic Oscillation mode, prevailing during the time of the Roman Warm Period.