Observational validation of the diffusive convection flux laws in the Amundsen Basin, Arctic Ocean
Observational validation of the diffusive convection flux laws in the Amundsen Basin, Arctic Ocean
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DOI：
10.1002/2015jc010884
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发表时间：
2015-12-01
影响因子：
3.6
通讯作者：
Morison, James
中科院分区：
文献类型：
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作者：
Guthrie, John D.;Fer, Ilker;Morison, James
在北冰洋的许多地区，低水平的机械驱动混合使得双扩散对流实际上成为将热量从大西洋水的核心向上移动到表面的唯一机制。为了量化北冰洋的双扩散热通量，作为北极环境观测站（NPEO） 2013年野外季节的一部分，在位于罗蒙诺索夫海岭附近的阿蒙森盆地（北纬89.5度，西经75度）的漂流冰站Barneo进行了温度微观结构实验。在150 ~ 250 m之间，几乎所有剖面都存在扩散对流温盐阶梯。高梯度界面的典型垂直热通量一直很小，为0(10(-1))W（-2）。我们的实验旨在解决阶梯问题，与早期使用不充分的仪器或采样的北极研究不同。与以前的研究相比，我们从温度微观结构中测量到的通量与实验室推导的通量定律吻合得很好，而以前的研究只能在2到4的范围内找到一致性。当使用最近的Flanagan等人[2013]的实验室推导时，测量和参数化热通量之间的相关性略高于Kelley[1990]中提出的更常用的推导。Nusselt与Rayleigh数标度表明，对流指数更接近于最近单组分对流数值模拟预测的0.29，而不是双组分扩散假设的典型1/3。然而，指数似乎对如何定义对流层高度很敏感。
The low levels of mechanically driven mixing in many regions of the Arctic Ocean make double diffusive convection virtually the only mechanism for moving heat up from the core of Atlantic Water towards the surface. In an attempt to quantify double diffusive heat fluxes in the Arctic Ocean, a temperature microstructure experiment was performed as a part of the North Pole Environmental Observatory (NPEO) 2013 field season from the drifting ice station Barneo located in the Amundsen Basin near the Lomonosov Ridge (89.5 degrees N, 75 degrees W). A diffusive convective thermohaline staircase was present between 150 and 250 m in nearly all of the profiles. Typical vertical heat fluxes across the high-gradient interfaces were consistently small, O(10(-1)) W m(-2). Our experiment was designed to resolve the staircase and differed from earlier Arctic studies that utilized inadequate instrumentation or sampling. Our measured fluxes from temperature microstructure agree well with the laboratory derived flux laws compared to previous studies, which could find agreement only to within a factor of two to four. Correlations between measured and parameterized heat fluxes are slightly higher when using the more recent Flanagan et al. [2013] laboratory derivation than the more commonly used derivation presented in Kelley [1990]. Nusselt versus Rayleigh number scaling reveals the convective exponent, , to be closer to 0.29 as predicted by recent numerical simulations of single-component convection rather than the canonical 1/3 assumed for double diffusion. However, the exponent appears to be sensitive to how convective layer height is defined.