Sensitivity of modern climate to the presence, strength and salinity of Mediterranean-Atlantic exchange in a global general circulation model
Sensitivity of modern climate to the presence, strength and salinity of Mediterranean-Atlantic exchange in a global general circulation model
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DOI：
10.1007/s00382-013-1680-5
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发表时间：
2014-02-01
期刊：
影响因子：
4.6
通讯作者：
Gutjahr, Marcus
中科院分区：
文献类型：
--
作者：
Ivanovic, Ruza F.;Valdes, Paul J.;Gutjahr, Marcus
地中海流出水（MOW）被认为是大西洋经向翻转环流（AMOC）强度和稳定性的关键因素，但地中海-大西洋水交换的未来是不确定的。它主要取决于地中海和大西洋之间的温度和盐度特征的差异，作为一个半封闭的盆地，地中海特别容易受到未来气候和用水变化的影响。当然，有强有力的地质证据表明，地中海在过去经历了剧烈的盐度和海平面波动。在这里，我们使用一个完全耦合的大气-海洋环流模式来研究地中海-大西洋交换变化对全球海洋环流和气候的影响。我们的研究结果表明，MOW加强并可能稳定AMOC，不是通过任何对NADW形成的贡献，而是通过向800米以下的南向大西洋洋流输送相对温暖的咸水。然而，我们几乎没有发现与地中海-大西洋气流强度变化相关的气候信号。另一方面，地中海的盐度控制着大西洋的MOW浮力，因此影响其与控制地面气候的浅层-中层环流模式的相互作用。地中海盐度的两个变化因素重组了北大西洋浅层环流，导致北大西洋、拉布拉多海和格陵兰-冰岛-挪威海的区域气候异常为+/- 4摄氏度或更高。尽管人们认为过去曾发生过如此大的盐度变化，但在不久的将来不太可能发生。然而，我们的工作确实表明，地中海水文平衡的变化可以影响全球范围的气候。
Mediterranean Outflow Water (MOW) is thought to be a key contributor to the strength and stability of Atlantic Meridional Overturning Circulation (AMOC), but the future of Mediterranean-Atlantic water exchange is uncertain. It is chiefly dependent on the difference between Mediterranean and Atlantic temperature and salinity characteristics, and as a semi-enclosed basin, the Mediterranean is particularly vulnerable to future changes in climate and water usage. Certainly, there is strong geologic evidence that the Mediterranean underwent dramatic salinity and sea-level fluctuations in the past. Here, we use a fully coupled atmosphere-ocean General Circulation Model to examine the impact of changes in Mediterranean-Atlantic exchange on global ocean circulation and climate. Our results suggest that MOW strengthens and possibly stabilises the AMOC not through any contribution towards NADW formation, but by delivering relatively warm, saline water to southbound Atlantic currents below 800 m. However, we find almost no climate signal associated with changes in Mediterranean-Atlantic flow strength. Mediterranean salinity, on the other hand, controls MOW buoyancy in the Atlantic and therefore affects its interaction with the shallow-intermediate circulation patterns that govern surface climate. Changing Mediterranean salinity by a factor of two reorganises shallow North Atlantic circulation, resulting in regional climate anomalies in the North Atlantic, Labrador and Greenland-Iceland-Norwegian Seas of +/- 4 A degrees C or more. Although such major variations in salinity are believed to have occurred in the past, they are unlikely to occur in the near future. However, our work does suggest that changes in the Mediterranean's hydrological balance can impact global-scale climate.