Vertical density gradient in the eastern North Atlantic during the last 30,000 years
Vertical density gradient in the eastern North Atlantic during the last 30,000 years
复制标题
DOI：
10.1007/s00382-011-1148-4
复制
发表时间：
2012-08
期刊：
影响因子：
4.6
通讯作者：
M. Rogerson;G. Bigg;E. Rohling;J. Ramirez
中科院分区：
文献类型：
--
作者：
M. Rogerson;G. Bigg;E. Rohling;J. Ramirez
过去海洋环流的密度和动量结构的变化是大西洋经向翻转环流和气候变化的一个重要方面。然而，人们对海洋垂直密度结构过去的变化知之甚少，即使是对北大西洋等系统进行了广泛研究。在这里，我们利用来自直布罗陀海峡的密集的地中海水羽沉降深度的物理控制，以获得第一个强大的，基于观测的，概率重建的垂直密度梯度在北大西洋东部在过去的30,000年。我们发现，这个梯度减弱了50%以上，相对于现在，在最后一次冰期最大，一般的变化与AMOC强度的减少。然而，我们发现只有一个小的变化，在海因里希事件1相对于末次冰期最大，尽管有强有力的证据表明，推翻了重大改变。这意味着，千年尺度的变化可能不会反映在海洋的垂直密度结构，这可能是有限的海洋翻转时间尺度或更长的响应。无论如何，我们的新的大西洋密度结构重建可以用作基于模型的AMOC重建验证的动力学措施的基础。此外，我们的一般方法是可转移到其他边缘海外流羽流，在其他位置提供海洋垂直密度梯度的估计。
Past changes in the density and momentum structure of oceanic circulation are an important aspect of changes in the Atlantic Meridional Overturning Circulation and consequently climate. However, very little is known about past changes in the vertical density structure of the ocean, even very extensively studied systems such as the North Atlantic. Here we exploit the physical controls on the settling depth of the dense Mediterranean water plume derived from the Strait of Gibraltar to obtain the first robust, observations-based, probabilistic reconstruction of the vertical density gradient in the eastern North Atlantic during the last 30,000 years. We find that this gradient was weakened by more than 50%, relative to the present, during the last Glacial Maximum, and that changes in general are associated with reductions in AMOC intensity. However, we find only a small change during Heinrich Event 1 relative to the Last Glacial Maximum, despite strong evidence that overturning was substantially altered. This implies that millennial-scale changes may not be reflected in vertical density structure of the ocean, which may be limited to responses on an ocean-overturning timescale or longer. Regardless, our novel reconstruction of Atlantic density structure can be used as the basis for a dynamical measure for validation of model-based AMOC reconstructions. In addition, our general approach is transferrable to other marginal sea outflow plumes, to provide estimates of oceanic vertical density gradients in other locations.