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North Atlantic climate responses to perturbations in Antarctic Intermediate Water

机译：北大西洋对南极中间水摄动的气候响应

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Recent observations suggest Antarctic Intermediate Water (AAIW) properties are changing. The impact of such variations is explored using idealised perturbation experiments with a coupled climate model, HadCM3. AAIW properties are altered between 10 and 20°S in the South Atlantic, maintaining constant potential density. The perturbed AAIW remains subsurface in the South Atlantic, but as it moves northwards, it surfaces and interacts with the atmosphere leading to density anomalies due to heat exchanges. For a cooler, fresher AAIW, there is a significant decrease in the mean North Atlantic sea surface temperature (SST), of up to 1°C, during years 51-100. In the North Atlantic Current region there are persistent cold anomalies from 2,000 m depth to the surface, and in the overlying atmosphere. Atmospheric surface pressure increases over the mid-latitude Atlantic, and precipitation decreases over northwest Africa and southwest Europe. Surface heat flux anomalies show that these impacts are caused by changes in the ocean rather than atmospheric forcing. The SST response is associated with significant changes in the Atlantic meridional overturning circulation (MOC). After 50 years there is a decrease in the MOC that persists for the remainder of the simulation, resulting from changes in the column-averaged density difference between 30°S and 60°N. Rather than showing a linear response, a warmer, saltier AAIW also leads to a decreased MOC strength for years 51-100 and resulting cooling in the North Atlantic. The non-linearity can be attributed to opposing density responses as the perturbed water masses interact with the atmosphere.
机译：最近的观察表明，南极中间水（AAIW）的性质正在发生变化。使用理想的摄动实验和耦合气候模型HadCM3，探索了这种变化的影响。南大西洋的AAIW特性在10至20°S之间改变，从而保持恒定的电位密度。扰动的AAIW仍在南大西洋的地下，但随着向北移动，它会与大气层接触并相互作用，从而由于热交换而导致密度异常。对于凉爽，新鲜的AAIW，在51至100年间，北大西洋平均海表温度（SST）显着下降，最高可达1°C。在北大西洋洋流地区，从地表到地面以及上层大气中，从2000 m深度一直存在持续的冷异常。在中纬度大西洋上，大气表面压力增加，而在西北非洲和西南欧洲，降水减少。地表热通量异常表明，这些影响是由海洋变化而不是大气强迫引起的。 SST响应与大西洋子午倾覆环流（MOC）的显着变化有关。 50年后，由于在30°S和60°N之间的列平均密度差的变化，MOC的下降在模拟的其余部分中持续存在。较温暖，更咸的AAIW并没有表现出线性响应，还导致51-100年间MOC强度降低，并导致北大西洋降温。当扰动的水团与大气相互作用时，非线性可归因于相反的密度响应。

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