| XIA Ruibin,LIU Chengyan,CHENG Chen. 2018. On the subtropical Northeast Pacific mixed layer depth and its influence on the subduction. Acta Oceanologica Sinica, 37(3):51－62 |
| On the subtropical Northeast Pacific mixed layer depth and its influence on the subduction |
| 副热带东北太平洋混合层深度及其对潜沉的影响 |
| Received:June 04, 2017 |
| DOI：10.1007/s13131-017-1102-3 |
| Key words:mixed layer depth mixed layer depth front subduction horizontal temperature advection nonuniform |
| 中文关键词: 混合层深度 混合层深度锋面 潜沉 水平热平流 不均匀分布 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41606217, 41675064 and 41406214; the Scientific Research Foundation for the Talent Start-Up of University of Information Science and Technology under contract No. 2015r043; the Open Fund of the Key Laboratory of Research on Marine Hazards Forecasting under contract No. LOMF1702; the China Scholarship Council under contract No. 201708320046. |
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| Abstract: |
| The present climate simulations of the mixed layer depth (MLD) and the subduction rate in the subtropical Northeast Pacific are investigated based on nine of the CMIP5 models. Compared with the observation data, spatial patterns of the MLD and the subduction rate are well simulated in these models. The spatial pattern of the MLD is nonuniform, with a local maximum MLD (>140 m) region centered at (28°N, 135°W) in late winter. The nonuniform MLD pattern causes a strong MLD front on the south of the MLD maximum region, controls the lateral induction rate pattern, and then decides the nonuniform distribution of the subduction rate. Due to the inter-regional difference of the MLD, we divide this area into two regions. The relatively uniform Ekman pumping has little effect on the nonuniform subduction spatial pattern, though it is nearly equal to the lateral induction in values. In the south region, the northward warm Ekman advection (-1.75×10-7 K/s) controls the ocean horizontal temperature advection (-0.85×10-7 K/s), and prevents the deepening of the MLD. In the ensemble mean, the contribution of the ocean advection to the MLD is about -29.0 m/month, offsetting the sea surface net heat flux contribution (33.9 m/month). While in the north region, the southward cold advection deepens the MLD (21.4 m/month) as similar as the heat flux (30.4 m/month). In conclusion, the nonuniform MLD pattern is dominated by the nonuniform ocean horizontal temperature advection. This new finding indicates that the upper ocean current play an important role in the variability of the winter MLD and the subduction rate. |
| 中文摘要: |
| 本文利用九个CMIP5 模式的模拟结果对副热带东北太平洋混合层深度（MLD）和潜沉率在现在气候背景下的特征进行了探究。与观测数据相比，模式结果能够较好的模拟MLD 和潜沉率的空间分布结构。MLD 的空间分布是不均匀的，晚冬在（28°N, 135°W）存在一个局地大值区（>140 m）。MLD 的不均匀分布导致在局地最大值区域以南形成了强的MLD 锋面，控制了侧向潜沉率的分布，继而决定了潜沉率的不均匀分布特征。根据MLD 区域间差异性的特征，我们将该海区分成了两个区域。尽管在数值大小上与侧向潜沉率相当，相对均匀的艾克曼抽吸对潜沉率空间不均匀性的贡献非常小。在南区，向北的暖艾克曼平流(-1.75×10-7 K/s)控制了上层海洋热平流(-0.85×10-7 K/s)，阻碍着MLD 的加深。在模式集合平均结果中，该海洋平流对MLD 的贡献大约为-29.0 m/mon，导致了与热通量贡献（33.9 m/mon）的抵消。然而在北区，向南的冷平流有利于MLD 的加深（21.4 m/mon），与海表热通量的贡献（30.4 m/mon）接近。总之，MLD 不均匀分布是由海洋热平流的不均匀分布决定的。该发现暗示着上层海洋流动对冬季MLD 和潜沉的变化起到重要作用。 |
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