| 副热带东北太平洋混合层深度及潜沉率季节循环对全球变暖的响应 |
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| 引用本文： | 王艺珊,夏瑞彬.副热带东北太平洋混合层深度及潜沉率季节循环对全球变暖的响应[J].海洋学报,2022,44(10):35-48. |
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| 作者姓名： | 王艺珊 夏瑞彬 |
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| 作者单位： | 1.南京信息工程大学 海洋科学学院，江苏 南京 210044 |
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| 基金项目： | 国家自然科学基金青年科学基金（41606217）；自然资源部海洋环境信息保障技术重点实验室开放基金。 |
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| 摘 要： | 本文利用第五次国际耦合模式比较计划（CMIP5）中的地球系统模式（ESM2M），结合Argo观测数据和由Ishii等整理的再分析数据集，分析现在气候背景和辐射强迫极端增强下副热带东北太平洋海域（10°～40°N，110°～160°W）混合层深度（MLD）和潜沉率的季节变化特征，研究其对全球变暖的响应。在现在气候背景下，二者最大值均出现在冬季。潜沉率的主要贡献项存在显著的季节变化差异，1?5月主要受侧向潜沉率的变化控制，6?12月则由风应力旋度导致的埃克曼抽吸速度变化主控。全球变暖后，季节循环信号的主控要素不变。但受风应力旋度等要素变化的影响，各季节的MLD减小，大值区范围收缩。由于冬季减小幅度远大于夏季，MLD季节波动幅度（振幅）显著变小。长期看，MLD呈现持续变浅的趋势，其空间不均匀性减弱引起的MLD锋面减弱是控制侧向潜沉率减弱，最终导致总潜沉率减弱的关键。由于埃克曼抽吸速度的季节变化信号对全球变暖的响应较小，因此总潜沉率在冬季受全球变暖的影响最为强烈。上述结果表明，构成潜沉率的两个关键要素对总潜沉率的贡献比例是随着季节变化而改变的:冬季MLD锋面强盛时期，侧向潜沉率的影响将显著增强。全球变暖前后二者截然不同的变化会显著改变潜沉率的季节循环振幅，可能对该区域模态水的形成和输运产生深远的影响。
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| 关 键 词： | 混合层深度 潜沉率 副热带东北太平洋 全球变暖 |
| 收稿时间： | 2021-12-04 |
Responses of seasonal cycles of the mixed layer depth and subduction rate to global warming in the subtropical Northeast Pacific |
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| Institution: | 1.School of Marine Science, Nanjing University of Information Science and Technology, Nanjing 210044, China2.Nanjing Xinda Institute of Safety and Emergency Management, Nanjing 210044, China |
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| Abstract: | Based on the Earth System Model (ESM2M) of the Coupled Model Intercomparison Project 5 (CMIP5), combined with Argo observation data and the reanalysis dataset compiled by Ishii et al., this paper presents the seasonal variation characteristics of mixed layer depth (MLD) and subduction process in the subtropical Northeast Pacific Ocean (10°?40°N, 110°?160°W) under the present climate background and extreme enhancement of radiative forcing are presented, to study its response to global warming. Under the current climate background, both of MLD and subduction rate reach their maximum values in winter. The main contribution items of subduction rate have significant seasonal variation. From January to May, the subduction rate is mainly controlled by the change of lateral induction rate, while from June to December, the main mechanism is the change of Ekman pumping velocity controlled by wind stress curl. After global warming, the main control elements of seasonal signals remain unchanged. However, under the influences of wind stress curl and other factors, the MLD in each season decreased and the range of the core maximum region shrinks. As the decrease in winter is much larger than that in summer, the seasonal fluctuation range (amplitude) of MLD is significantly smaller. In the long run, MLD shows a trend of continuous shallower, and the weakening of MLD front caused by the weakening of its spatial non-uniformity is the key to control the weakening of lateral induction rate and eventually lead to the weakening of the subduction rate. Since the seasonal variation signal of Ekman pumping velocity has little response to global warming, subduction rate is most strongly affected in winter. The results show that the contribution proportion of the two key factors to the subduction rate changes with the seasons: when the MLD front is strong in winter, the influence of the lateral induction rate will be significantly enhanced. The different variations of the two factors before and after global warming will significantly change the seasonal amplitude of the subduction rate, which may have a profound impact on the formation and transport of mode water in the region. |
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