Mixed layer instabilities and restratification
Mixed layer instabilities and restratification
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DOI：
10.1175/jpo3101.1
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发表时间：
2007-09-01
影响因子：
3.5
通讯作者：
Fox-Kemper, Baylor
中科院分区：
文献类型：
--
作者：
Boccaletti, Giulio;Ferrari, Raffaele;Fox-Kemper, Baylor
研究了由表面密度场横向梯度引起的海洋表面混合层的重新分层。横向梯度显示出对地转斜压不稳定性和从水平到垂直的坍落不稳定。这些不稳定性被称为混合层不稳定性 (MLI)，由于表面分层较弱，因此与海洋内部的不稳定性不同。空间尺度为O(1-10)km，生长时间尺度为一天量级。线性稳定性分析和全非线性模拟用于研究 MLI 及其对混合层再分层的影响。主要结果是 MLI 是 ML 热预算中的一个主序过程，用于不断重新分层表面海洋。气候和区域海洋模型无法解析与 MLI 相关的尺度，并且可能低估 ML 重新分层的速率，从而导致海面温度和 ML 深度出现偏差。在即将发表的论文中，作者讨论了一种参数化方案，以将 MLI 的影响纳入海洋模型中。
The restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied. The lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical. These instabilities, which are referred to as mixed layer instabilities (MLIs), differ from instabilities in the ocean interior because of the weak surface stratification. Spatial scales are O(1-10) km, and growth time scales are on the order of a day. Linear stability analysis and fully nonlinear simulations are used to study MLIs and their impact on mixed layer restratification. The main result is that MLIs are a leading-order process in the ML heat budget acting to constantly restratify the surface ocean. Climate and regional ocean models do not resolve the scales associated with MLIs and are likely to underestimate the rate of ML restratification and consequently suffer from a bias in sea surface temperatures and ML depths. In a forthcoming paper, the authors discuss a parameterization scheme to include the effect of MLIs in ocean models.