The seasonal cycle of submesoscale flows
The seasonal cycle of submesoscale flows
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DOI：
10.1016/j.ocemod.2015.05.002
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发表时间：
2015-08-01
期刊：
影响因子：
3.2
通讯作者：
Nurser, A. J. George
中科院分区：
文献类型：
--
作者：
Brannigan, Liam;Marshall, David P.;Nurser, A. J. George
在一个理想化的模式域类似于中纬度开放的海洋地区的季节循环的次中尺度流在上层海洋进行了研究。次中尺度过程变得更强的分辨率增加，但有限的证据收敛的解决方案。锋生过程增加水平浮力梯度时，混合层在夏季较浅，而翻转不稳定性减弱的水平浮力梯度的混合层加深在冬季。地面温度和速度的水平波数谱斜率夏季较陡，冬季较浅。这是一致的，随着混合层的加深和次中尺度的能量化，混合层的不稳定性增强。随着分辨率的提高，地转平衡的程度福尔斯下降，随着混合层的加深，更强的非线性和高频过程的证据变得更加重要。Ekman浮力通量可以比地面冷却强得多，并且在设置层结和锋的位涡方面是局部主导的，特别是在初冬。在冬季，高达30%的混合层体积具有负位涡和对称不稳定的预测内的中尺度涡以及在锋面区域外的涡。(C)2015作者由爱思唯尔有限公司发布
The seasonal cycle of submesoscale flows in the upper ocean is investigated in an idealised model domain analogous to mid-latitude open ocean regions. Submesoscale processes become much stronger as the resolution is increased, though with limited evidence for convergence of the solutions. Frontogenetical processes increase horizontal buoyancy gradients when the mixed layer is shallow in summer, while overturning instabilities weaken the horizontal buoyancy gradients as the mixed layer deepens in winter. The horizontal wavenumber spectral slopes of surface temperature and velocity are steep in summer and then shallow in winter. This is consistent with stronger mixed layer instabilities developing as the mixed layer deepens and energising the submesoscale. The degree of geostrophic balance falls as the resolution is made finer, with evidence for stronger non-linear and high-frequency processes becoming more important as the mixed layer deepens. Ekman buoyancy fluxes can be much stronger than surface cooling and are locally dominant in setting the stratification and the potential vorticity at fronts, particularly in the early winter. Up to 30% of the mixed layer volume in winter has negative potential vorticity and symmetric instability is predicted inside mesoscale eddies as well as in the frontal regions outside of the vortices. (C) 2015 The Authors. Published by Elsevier Ltd.