Thermohaline structure in the California Current System: Observations and modeling of spice variance
Thermohaline structure in the California Current System: Observations and modeling of spice variance
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DOI：
10.1029/2011jc007589
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发表时间：
2012-02
影响因子：
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通讯作者：
R. Todd;D. Rudnick;M. Mazloff;B. Cornuelle;R. Davis
中科院分区：
文献类型：
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作者：
R. Todd;D. Rudnick;M. Mazloff;B. Cornuelle;R. Davis
[1]利用自主水下滑翔机的持续观测和数值状态估计，研究了加利福尼亚洋流系统中的上层海洋温盐结构。观测和状态估计都显示，各层由等长线上的温度和盐度变化(即，香料变化)来区分。残留混合层的中、亚中尺度SPICE方差最大，在26.3 kg m−-3附近跃层以下降至最小，然后在26.6 kg m−-3附近再次增大。在大尺度SPICE梯度大(小)的等温线上出现高(低)中尺度SPICE方差，这与大尺度梯度的搅动产生较小的温盐结构相一致。状态估计中的被动示踪剂伴随计算用于研究SPICE变化层形成的可能机制。残留混合层中的高香料方差层具有明显的成因，并与命名水团有关；残留混合层中高香料方差层的水来自北方，为太平洋亚北极区水，而深层高香料方差层的水为南方水，为赤道太平洋水。26.3kgm−-3附近的低香料变异层位于命名水团之间，没有明确的来源。相对于数值模拟中设定的扩散系数，有效水平扩散系数κh和有效昼夜扩散系数κv都有所增加，但κh和κv随深度的变化不足以解释观测到的温盐结构分层。
[1] Upper ocean thermohaline structure in the California Current System is investigated using sustained observations from autonomous underwater gliders and a numerical state estimate. Both observations and the state estimate show layers distinguished by the temperature and salinity variability along isopycnals (i.e., spice variance). Mesoscale and submesoscale spice variance is largest in the remnant mixed layer, decreases to a minimum below the pycnocline near 26.3 kg m−3, and then increases again near 26.6 kg m−3. Layers of high (low) meso- and submesoscale spice variance are found on isopycnals where large-scale spice gradients are large (small), consistent with stirring of large-scale gradients to produce smaller scale thermohaline structure. Passive tracer adjoint calculations in the state estimate are used to investigate possible mechanisms for the formation of the layers of spice variance. Layers of high spice variance are found to have distinct origins and to be associated with named water masses; high spice variance water in the remnant mixed layer has northerly origin and is identified as Pacific Subarctic water, while the water in the deeper high spice variance layer has southerly origin and is identified as Equatorial Pacific water. The layer of low spice variance near 26.3 kg m−3 lies between the named water masses and does not have a clear origin. Both effective horizontal diffusivity, κh, and effective diapycnal diffusivity, κv, are elevated relative to the diffusion coefficients set in the numerical simulation, but changes in κh and κv with depth are not sufficient to explain the observed layering of thermohaline structure.