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首页> 外文期刊>Journal of oceanography >Interdecadal Temperature Variations in the North Pacific Central Mode Water Simulated by an OGCM
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Interdecadal Temperature Variations in the North Pacific Central Mode Water Simulated by an OGCM

机译：OGCM模拟的北太平洋中央模式水的年代际温度变化

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The North Pacific Central Mode Water (CMW) is a water mass that forms in the Kuroshio-Oyashio Extension (KOE) region with characteristic low potential vorticity. Recent studies have suggested that the CMW, as low potential vorticity water, plays an important role in the adjustment of the subtropical gyre and subsurface variability on decadal to interdecadal timescales. We have forced a realistic ocean general circulation model (OGCM) with observed wind stress and sea surface temperature (SST) forcing to investigate the decadal variations of the CMW. Associated with the large atmospheric changes after the mid-1970s climate regime shift, the upper thermocline experiences a cooling as negative SST anomalies in the central North Pacific are subducted and advected southward. In addition to this thermodynamic response, the CMW's path shifts anomalously eastward in response to anomalous Ekman pumping. This eastward shift of the core of the CMW produces a lowering of the isotherms, and a consequent warming, on the path of the CMW core. This warming partially counteracts the cooling associated with subducted surface anomalies, and it may be responsible for the reduced temperature variations at the climatological position of the CMW when both anomalous wind and heat fluxes are given. Lateral induction across the sloping bottom of the winter mixed layer in the KOE is critical to the formation of the low potential vorticity CMW. Coarse resolution models, which are widely used in climate modeling, underestimate the horizontal gradient of the mixed layer depth and form only a weak CMW or none at all. We have conducted a coarse resolution experiment with the same OGCM, showing that the subsurface response is much reduced. In particular, there is no dynamic warming in the CMW and the thermodynamic response to the SST cooling dominates. The resultant total response differs substantially from that in the finer resolution run where a strong CMW forms. This sensitivity to the model resolution corroborates the important dynamical role that the CMW may play with its distinctive low potential vorticity character and calls for its improved simulation.
机译：北太平洋中央模式水（CMW）是在黑潮-尾潮扩展区（KOE）地区形成的水团，具有低潜在涡度。最近的研究表明，作为低潜在涡度水的CMW，在年代际到年代际时间尺度的亚热带回旋和地下变率的调整中起着重要作用。我们已经通过观察风应力和海面温度（SST）强迫建立了逼真的海洋总体环流模型（OGCM），以研究CMW的年代际变化。与1970年代中期气候变化后的大气变化有关，由于北太平洋中部的负SST异常向南俯冲并向南平移，上层跃层正经历降温。除了这种热力学响应之外，CMW的路径还响应异常的Ekman泵送而异常向东移动。 CMW核芯的这种向东移动会降低CMW核芯路径上的等温线并因此变暖。这种变暖部分抵消了与俯冲的表面异常有关的冷却，并且当给出异常的风和热通量时，这可能是导致CMW气候位置温度变化减小的原因。在KOE中，冬季混合层倾斜底部的横向感应对于形成低潜在涡度CMW至关重要。在气候模拟中广泛使用的粗分辨率模型低估了混合层深度的水平梯度，并且仅形成了弱CMW或根本没有形成。我们使用相同的OGCM进行了粗分辨率实验，结果表明地下响应大大降低了。特别是，在CMW中没有动态升温，并且对SST冷却的热力学响应占主导地位。最终的总响应与形成强CMW的较高分辨率运行有很大不同。对模型分辨率的这种敏感性证实了CMW可能以其独特的低潜在涡度特性发挥重要的动力学作用，并呼吁对其进行改进的仿真。

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