| 摘要: |
| 使用一个全球海洋环流模式的18 a(1993～2010 年)数据, 对北太平洋副热带中部模态水(CMW)潜沉区混合层内热收支的空间分布状况及其季节和年际变率特征进行了分析, 并重点讨论了热收支与太平洋年代际震荡(PDO)之间的相互关联。结果表明, CMW 潜沉区的热收支是海表热力强迫与海洋动力过程之间的平衡。其中混合作用, 特别是湍流扩散是海洋动力过程的主要分量, 对该海区混合层内部的热量耗散起到关键的作用。该海区的热收支具有显著的季节变化信号, 在春夏季与秋冬季存在明显的差异。热收支的年际变化与PDO 的超前滞后相关性分析表明, 该海区的混合层温度(MLT)具有显著的PDO 信号, 同时 PDO 与 MLT 两者随时间的变化信号( ?[P]/?t 与?[T]/?t )之间也有强相关性。?[P]/?t与海表热力强迫项(SEF)显著的相关性表明, SEF 可能会对PDO信号的产生及变化过程产生重要的影响;?[P]/?t 与夹卷项的高相关性则间接证明潜沉的 CMW 的温度存在 PDO 信号; 作为海洋动力过程的主体, 扩散项和平流项均会对PDO 信号变化做出滞后响应。本研究增进了对CMW 潜沉区混合层内海水温度变化特征的认识。 |
| 关键词: 中部模态水(CMW) 北太平洋 潜沉 热收支 太平洋年代际震荡(PDO) |
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| 基金项目:国家重点基础研究发展计划(2012CB417402, 2012CB956001);国家自然科学基金(40876011) |
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| Heat budget in the subduction region of the North Pacific central mode water as revealed by a global general circulation model |
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| Abstract: |
| The mixed layer heat budget in the subduction region of the North Pacific mode water (CMW) was evaluated with 18 years (1993～2010) data obtained using a global general circulation model (GCM). The spatial distribution, seasonal cycle and annual variability of the CMW were investigated. The relationship between the heat budget and the Pacific Decadal Oscillation (PDO) was analyzed emphatically. The results demonstrated that the heat budget in this region was a balance between surface heat forcing and ocean dynamic process. The mixing effect, especially the turbulent diffusion was the dominant component of ocean dynamic process, which played the key role in the dissipation of heat in this region. There was strong seasonal cycle in the temperature and heat budget of this region, which was driven by seasonality in heat flux and mixed layer depth. During the spring and summer, the mixed layer depth (MLD) became very shallow and stable, and the surface forcing was the main factor in controlling the temporal variability of mixed layer temperature (MLT). Meanwhile the ocean dynamic process was relatively weak, of which the mixing was the main component. During the autumn and winter, a dramatic cooling effect on surface leaded to the quick deepening of MLD and subduction, making the vertical entrainment into the principal component of ocean dynamic process. On the contrary, although the mixing effect was still very important, its proportion becomes much smaller than that in spring and summer. The lagged correlation between PDO and heat budget in this region indicated that the MLT contained significant PDO signal. The correlation coefficient between the annual variability of heat budget and the temporal tendency of PDO was ?0.84. The temporal tendency of PDO was also found to be highly correlated to most components of the heat budget. It was shown from the high correlation to the surface forcing that the surface forcing might have important effect on the evolution of PDO. It was suggested from the high correlation to the vertical entrainment that the subducted CMW was very possible to carry the PDO signal. As the main ocean dynamic processes, the mixing and advection seemed to be passively reacted to the variability of PDO. |
| Key words: central mode water the North Pacific subduction heat budget PDO(the Pacific Decadal Osciuation) |
