Effect of global ocean temperature change on deep ocean ventilation
Effect of global ocean temperature change on deep ocean ventilation
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DOI：
10.1029/2005pa001242
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发表时间：
2007-05-09
期刊：
影响因子：
--
通讯作者：
Russell, J. L.
中科院分区：
文献类型：
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作者：
de Boer, A. M.;Sigman, D. M.;Russell, J. L.
越来越多的古海洋学观察表明，在温暖的气候中，海洋的深度通风比在寒冷的气候中更强。在这里，我们使用一个一般的海洋环流模式来检验这一假设，即这种关系是由于低平均温度下海水密度对温度的敏感性降低所致，即在较低温度下，表面冷却在增密淡水极地水域和引发对流方面不那么有效。为了将这一因素与其他与气候有关的反馈分离开来，我们只在模型海洋温度用于计算密度(以下我们将其称为“动态‘’温度变化”)时才更改该模型。我们发现，在全球范围内，动态寒冷的海洋比动态温暖的海洋通风更少。随着动力冷却，在盐跃层较强的地区(即南大洋和北太平洋)，对流明显减少，而在正盐度浮力最小的极地北大西洋，对流则反转增加。我们认为，北大西洋与南大洋和北太平洋的这种相反的行为是能量受限倾覆的结果。
A growing number of paleoceanographic observations suggest that the ocean's deep ventilation is stronger in warm climates than in cold climates. Here we use a general ocean circulation model to test the hypothesis that this relation is due to the reduced sensitivity of seawater density to temperature at low mean temperature; that is, at lower temperatures the surface cooling is not as effective at densifying fresh polar waters and initiating convection. In order to isolate this factor from other climate-related feedbacks we change the model ocean temperature only where it is used to calculate the density ( to which we refer below as "dynamic'' temperature change). We find that a dynamically cold ocean is globally less ventilated than a dynamically warm ocean. With dynamic cooling, convection decreases markedly in regions that have strong haloclines ( i.e., the Southern Ocean and the North Pacific), while overturning increases in the North Atlantic, where the positive salinity buoyancy is smallest among the polar regions. We propose that this opposite behavior of the North Atlantic to the Southern Ocean and North Pacific is the result of an energy-constrained overturning.