Sriver Ryan L, Huber Matthew
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Nature. 2007 May 31;447(7144):577-80. doi: 10.1038/nature05785.
Ocean mixing affects global climate and the marine biosphere because it is linked to the ocean's ability to store and transport heat and nutrients. Observations have constrained the magnitude of upper ocean mixing associated with certain processes, but mixing rates measured directly are significantly lower than those inferred from budget analyses, suggesting that other processes may play an important role. The winds associated with tropical cyclones are known to lead to localized mixing of the upper ocean, but the hypothesis that tropical cyclones are important mixing agents at the global scale has not been tested. Here we calculate the effect of tropical cyclones on surface ocean temperatures by comparing surface temperatures before and after storm passage, and use these results to calculate the vertical mixing induced by tropical cyclone activity. Our results indicate that tropical cyclones are responsible for significant cooling and vertical mixing of the surface ocean in tropical regions. Assuming that all the heat that is mixed downwards is balanced by heat transport towards the poles, we calculate that approximately 15 per cent of peak ocean heat transport may be associated with the vertical mixing induced by tropical cyclones. Furthermore, our analyses show that the magnitude of this mixing is strongly related to sea surface temperature, indicating that future changes in tropical sea surface temperatures may have significant effects on ocean circulation and ocean heat transport that are not currently accounted for in climate models.
海洋混合影响全球气候和海洋生物圈，因为它与海洋储存和传输热量及营养物质的能力相关。观测已经限制了与某些过程相关的上层海洋混合的程度，但直接测量的混合速率显著低于从收支分析推断出的速率，这表明其他过程可能起着重要作用。已知与热带气旋相关的风会导致上层海洋的局部混合，但热带气旋在全球尺度上是重要混合因子这一假设尚未得到验证。在这里，我们通过比较风暴经过前后的海面温度来计算热带气旋对海洋表面温度的影响，并利用这些结果计算热带气旋活动引起的垂直混合。我们的结果表明，热带气旋导致热带地区海洋表面显著降温及垂直混合。假设所有向下混合的热量由向极地的热量传输平衡，我们计算得出，海洋热量传输峰值的约15%可能与热带气旋引起的垂直混合有关。此外，我们的分析表明，这种混合的程度与海面温度密切相关，这表明热带海面温度未来的变化可能对海洋环流和海洋热量传输产生重大影响，而目前气候模型并未考虑这些影响。
