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首页> 外文期刊>Journal of Physical Oceanography >Low-Frequency Pycnocline Variability in the Northeast Pacific
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Low-Frequency Pycnocline Variability in the Northeast Pacific

机译：东北太平洋低频台球菌的变异性

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摘要

The output from an ocean general circulation model (OGCM) driven by observed surface forcing is used in conjunction with simpler dynamical models to examine the physical mechanisms responsible for inter-annual to interdecadal pycnocline variability in the northeast Pacific Ocean during 1958-97, a period that includes the 1976-77 climate shift. After 1977 the pycnocline deepened in a broad band along the coast and shoaled in the central part of the Gulf of Alaska. The changes in pycnocline depth diagnosed from the model are in agreement with the pycnocline depth changes observed at two ocean stations in different areas of the Gulf of Alaska. A simple Ekman pumping model with linear damping explains a large fraction of pycnocline variability in the OGCM. The fit of the simple model to the OGCM is maximized in the central part of the Gulf of Alaska, where the pycnocline variability produced by the simple model can account for ～70%-90% of the pycnocline depth variance in the OGCM. Evidence of westward-propagating Rossby waves is found in the OGCM, but they are not the dominant signal. On the contrary, large-scale pycnocline depth anomalies have primarily a standing character, thus explaining the success of the local Ekman pumping model. The agreement between the Ekman pumping model and OGCM deteriorates in a large band along the coast, where propagating disturbances within the pycnocline, due to either mean flow advection or boundary waves, appear to play an important role in pycnocline variability. Coastal propagation of pycnocline depth anomalies is especially relevant in the western part of the Gulf of Alaska, where local Ekman pumping-induced changes are anticorrelated with the OGCM pycnocline depth variations. The pycnocline depth changes associated with the 1976-77 climate regime shift do not seem to be consistent with Sverdrup dynamics, raising questions about the nature of the adjustment of the Alaska Gyre to low-frequency wind stress variability.
机译：由观测到的表面强迫驱动的海洋总环流模型（OGCM）的输出与更简单的动力学模型一起使用，以检查造成1958-97年（东北）期间太平洋东北部年际至年代际线变化的物理机制。其中包括1976-77年的气候变化。 1977年以后，比考克林在沿海沿一条宽阔带加深，并在阿拉斯加海湾的中部浅滩。根据该模型诊断出的比考诺克深度变化与在阿拉斯加湾不同地区的两个海洋站观测到的比诺考克深度变化一致。具有线性阻尼的简单Ekman抽运模型解释了OGCM的比诺可林变化很大。简单模型对OGCM的拟合在阿拉斯加湾的中部达到最大，在该模型中，简单模型所产生的比索球面变异可占OGCM约比球面深度变化的70％-90％。在OGCM中发现了向西传播的Rossby波的证据，但它们不是主要信号。相反，大规模的比索斜线深度异常主要具有站立特征，因此可以解释局部埃克曼抽水模型的成功。 Ekman抽水模型与OGCM之间的一致性在沿海岸的一个大带中恶化，在该带中，由于平均流对流或边界波，在pyococline内传播的扰动似乎在pyocococline的变化中起重要作用。吡咯啉深度异常的沿海传播在阿拉斯加湾的西部尤为重要，那里的局部埃克曼抽水诱导的变化与OGCM吡咯啉深度的变化是反相关的。与1976-77年气候变化有关的台球深度变化似乎与Sverdrup动力学不一致，这引发了人们对阿拉斯加涡流向低频风应力变化的调节性质的质疑。

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