South Atlantic intermediate water advances into the North-east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period
South Atlantic intermediate water advances into the North-east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period
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DOI：
10.1002/2016gc006281
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发表时间：
2016-06-01
影响因子：
3.5
通讯作者：
Frank, Norbert
中科院分区：
文献类型：
--
作者：
Dubois-Dauphin, Quentin;Bonneau, Lucile;Frank, Norbert
为了研究加迪斯湾近40 ka来的中层水动力学，对280-827 m深度的加迪斯湾和阿尔沃兰海海水和冷水珊瑚（CWC）样品的Nd同位素组成进行了研究。阿尔沃兰海和加迪斯湾北方冰川和全新世CWC的Nd值相对恒定（分别为-8.6至-9.0和-9.5至-10.4）。这些值与地中海外流水（MOW; Nd =-9.4）和地中海海水（MSW; Nd =-9.9）周围现今中层沃茨的值相似。相比之下，在加迪斯湾南部温跃层深度（550-827 m）收集的CWC的冰川Nd值显示出比现今值（-11.70.3）更高的平均值（-8.90.4）。这意味着地中海（MSW）或南大西洋起源（东南极中层水，EAAIW）的水团的相对贡献更高。我们的研究产生了第一个证据，显着的放射性成因Nd值（约-8）在19，23-24，和27 ka，这是同时代的冰山流量增加和大西洋经向翻转环流（AMOC）的减弱。由于MOW钕值保持稳定，在末次冰期，它建议，这些放射性成因钕值最有可能反映了增强向北传播的冰川EAAIW到大西洋盆地东部。
The Nd isotopic composition (epsilon Nd) of seawater and cold-water coral (CWC) samples from the Gulf of Cadiz and the Alboran Sea, at a depth of 280-827 m were investigated in order to constrain middepth water mass dynamics within the Gulf of Cadiz over the past 40 ka. epsilon Nd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cadiz reveals relatively constant values (-8.6 to -9.0 and -9.5 to -10.4, respectively). Such values are similar to those of the surrounding present-day middepth waters from the Mediterranean Outflow Water (MOW; epsilon Nd approximate to -9.4) and Mediterranean Sea Water (MSW; epsilon Nd approximate to -9.9). In contrast, glacial epsilon Nd values for CWC collected at thermocline depth (550-827 m) in the southern Gulf of Cadiz display a higher average value (-8.90.4) compared to the present-day value (-11.70.3). This implies a higher relative contribution of water masses of Mediterranean (MSW) or South Atlantic origin (East Antarctic Intermediate Water, EAAIW). Our study has produced the first evidence of significant radiogenic epsilon Nd values (approximate to -8) at 19, 23-24, and 27 ka, which are coeval with increasing iceberg discharges and a weakening of Atlantic Meridional Overturning Circulation (AMOC). Since MOW epsilon Nd values remained stable during the last glacial period, it is suggested that these radiogenic epsilon Nd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.