Mid- to late-Holocene oceanographic variability on the Southeast Greenland shelf
Mid- to late-Holocene oceanographic variability on the Southeast Greenland shelf
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DOI：
10.1177/0959683612460789
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发表时间：
2013-02-01
期刊：
影响因子：
2.4
通讯作者：
Pearce, C.
中科院分区：
文献类型：
--
作者：
Andresen, C. S.;Hansen, M. J.;Pearce, C.
通过分析来自同一地点的两个岩心的综合海洋沉积物记录，可以重建格陵兰岛东南部大陆架过去5800年的海洋变化。Fox04G/05R岩芯来自北大西洋西北部连接900 m深的Sermilik Fjord和Irminger海的交叉架槽的侧盆。对记录进行了粒度分布、XRF、底栖和浮游有孔虫含量分析，并根据Pb-210和C-14定年得到了年代。记录中晚全新世古海洋学变化的特征是记录开始时（5800 cal. yr BP）的伊明格海流（IC）和区域全新世气候最佳期（5200 - 4200 cal. yr BP）的显著影响。在3600 cal. yr BP之后，东格陵兰洋流（EGC）极地水的影响增加，新冰期的冷却减弱了东格陵兰洋流的影响。在1500 - 700 cal. yr BP之间，环境高度由寒冷的低盐度水团主导，其特征是海冰在局部形成和/或随着EGC的增强而输送。在700 cal. yr BP，与“小冰期”的开始一致，IC水团的流入加强了，特别是在北大西洋洋流的短暂变暖期间，这很可能与收缩的次极环流有关。与此同时，EGC极地水输运也加剧，导致大陆架上形成分层水柱，这可能有利于温暖的地下IC水的夹带。另外，相对温暖的东部次极环流边缘可能在此时促进了延伸的东南格陵兰出口冰川的强烈海底融化，产生了增强的融水流出，这有利于河口环流过程，维持了IC水团的流入。
A reconstruction of oceanographic variability of the past 5800 years on the southeast Greenland shelf was obtained by analysing a combined marine sediment record based on two cores from the same site. Cores Fox04G/05R were retrieved from a side basin to a cross-shelf trough connecting the 900 m deep Sermilik Fjord with the Irminger Sea in the northwestern North Atlantic. The record was analysed in terms of grain size distribution, XRF and benthic and planktonic foraminiferal content and the chronology was obtained on the basis of Pb-210 and C-14 dating. The late-Holocene paleoceanographic variations in the record were characterised by a marked influence from the Irminger Current (IC) at the onset of the record at 5800 cal. yr BP and the regional Holocene Climatic Optimum between 5200 and 4200 cal. yr BP. After 3600 cal. yr BP Neoglacial cooling with increased influence of polar waters from the East Greenland Current (EGC) diminished the influence from the IC. Between 1500 and 700 cal. yr BP, the environment was highly dominated by cold low-salinity water masses characterised by sea ice forming locally and/or transported with an intensified EGC. At 700 cal. yr BP, concordant with the onset of the 'Little Ice Age', inflow of IC water masses intensified, notably during short-lived warming episodes of the North Atlantic Current most likely related to a contracted subpolar gyre. At the same time, the EGC polar water transport also intensified leading to a stratified water column on the shelf and this may have favoured entrainment of warm subsurface IC waters. Alternatively, the relatively warm rim of the eastern subpolar gyre may have promoted intense submarine melting of extended Southeast Greenland outlet glaciers at this time, producing enhanced meltwater outflow which favoured estuarine circulation processes maintaining the inflow of IC water masses.