Persistent monsoonal forcing of Mediterranean Outflow Water dynamics during the late Pleistocene
Persistent monsoonal forcing of Mediterranean Outflow Water dynamics during the late Pleistocene
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DOI：
10.1130/g37013.1
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发表时间：
2015-11-01
期刊：
影响因子：
5.8
通讯作者：
Friedrich, O.
中科院分区：
文献类型：
--
作者：
Bahr, A.;Kaboth, S.;Friedrich, O.
全球海洋环流的模式和活力在很大程度上取决于平流到深水形成地点的(次)地表水的盐度。在大西洋子午线翻转环流(AMOC)内，高盐度水的一个重要供应者是地中海外流水(MOW)，它经由直布罗陀海峡排入北大西洋。尽管它对北大西洋盐度预算很重要，但对MOW产量的长期动态仍知之甚少。在这里，我们提供了来自加的斯湾内三个钻探地点的海底水流速度的高分辨率记录，这些记录记录了过去类似于150K.Y的持续低纬强迫MOW水流速度。我们证明，非洲季风通过其对地中海东部淡水收支的影响，是轨道尺度MOW变化的主要驱动因素。因此，MOW的形成与高纬度起源的百年尺度振荡叠加的轨道进动一致。我们进一步证明，北半球夏季日照极小值刺激了最大限度地将MOW衍生的盐分注入北大西洋，可能加强了AMOC的中间分支。MOW动力与低纬气候强迫的直接耦合代表了一个迄今被忽视的将热带气候信号传播(次)到北部高纬度的过程。
The mode and vigor of the global oceanic circulation critically depend on the salinity of (sub) surface water masses advected to the loci of deep-water formation. Within the Atlantic meridional overturning circulation (AMOC), an important supplier of high-salinity waters is the Mediterranean Outflow Water (MOW), discharging into the North Atlantic via the Strait of Gibraltar. Despite its importance for the North Atlantic salinity budget, the long-term dynamics of MOW production have remained poorly understood. Here we present high-resolution records of bottom-current velocity from three drill sites within the Gulf of Cadiz that document a persistent low-latitude forcing of MOW flow speed over the past similar to 150 k.y. We demonstrate that the African monsoon is the predominant driver of orbital-scale MOW variability via its influence on the freshwater budget of the eastern Mediterranean Sea. Consequently, MOW formation fluctuates in concert with orbital precession overprinted by centennial-scale oscillations of high-latitude origin. We further document that Northern Hemisphere summer insolation minima stimulate maximal injection of MOW-derived salt into the North Atlantic, likely strengthening the intermediate AMOC branch. The direct coupling of MOW dynamics to low-latitude climate forcing represents a hitherto neglected process for propagating (sub)tropical climate signals into the high northern latitudes.