在大部分非热带海洋中，季节循环由太阳辐射的季节变化支配。但在热带，海洋表面温度存在一个强季节循环，尽管辐射输入相对来说保持不变。James Moum及其同事发表了多年份观测结果，它们表明：来自下面的湍流混合占140° W处赤道太平洋“冷舌”中海平面温度的季节循环幅度的大部分。这些发现应能提高我们对“厄尔尼诺/南方涛动”循环的认识，帮助提高很多海洋-大气耦合气候模型的准确性。（生物谷 Bioon.com）
生物谷推荐的英文摘要
Nature doi:10.1038/nature12363
Seasonal sea surface cooling in the equatorial Pacific cold tongue controlled by ocean mixing
James N. Moum, Alexander Perlin, Jonathan D. Nash & Michael J. McPhaden
Sea surface temperature (SST) is a critical control on the atmosphere1, and numerical models of atmosphere–ocean circulation emphasize its accurate prediction. Yet many models demonstrate large, systematic biases in simulated SST in the equatorial ‘cold tongues’ (expansive regions of net heat uptake from the atmosphere) of the Atlantic2 and Pacific3 oceans, particularly with regard to a central but little-understood feature of tropical oceans: a strong seasonal cycle. The biases may be related to the inability of models to constrain turbulent mixing realistically4, given that turbulent mixing, combined with seasonal variations in atmospheric heating, determines SST. In temperate oceans, the seasonal SST cycle is clearly related to varying solar heating5; in the tropics, however, SSTs vary seasonally in the absence of similar variations in solar inputs6. Turbulent mixing has long been a likely explanation, but firm, long-term observational evidence has been absent. Here we show the existence of a distinctive seasonal cycle of subsurface cooling via mixing in the equatorial Pacific cold tongue, using multi-year measurements of turbulence in the ocean. In boreal spring, SST rises by 2 kelvin when heating of the upper ocean by the atmosphere exceeds cooling by mixing from below. In boreal summer, SST decreases because cooling from below exceeds heating from above. When the effects of lateral advection are considered, the magnitude of summer cooling via mixing (4 kelvin per month) is equivalent to that required to counter the heating terms. These results provide quantitative assessment of how mixing varies on timescales longer than a few weeks, clearly showing its controlling influence on seasonal cooling of SST in a critical oceanic regime.
