Intensification and poleward shift of subtropical western boundary currents in a warming climate
Intensification and poleward shift of subtropical western boundary currents in a warming climate
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DOI：
10.1002/2015jc011513
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发表时间：
2016-07
影响因子：
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通讯作者：
Hu Yang;G. Lohmann;Wei Wei-Wei;M. Dima;M. Ionita;Jiping Liu
中科院分区：
文献类型：
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作者：
Hu Yang;G. Lohmann;Wei Wei-Wei;M. Dima;M. Ionita;Jiping Liu
在过去的一个世纪里，在中纬度西部边界流(WBC)上观测到了海表面温度(SST)的显著升高。然而，由于观察有限，对这一现象的机制仍知之甚少。本文通过分析海表面温度(SST)、海面热通量、海水流速、海面风速和海平面气压(SLP)等几个耦合参数来识别WBCS的动态变化。使用了三种类型的独立数据集，包括再分析产品、卫星混合观测。和气候模型比较项目(CMIP5)第五阶段的气候模型产出。基于这些广泛的数据，我们发现，由于全球变暖的长期影响，WBC(墨西哥湾流除外)正在加强并向两极移动。近地表海风的加强和极移，归因于正的环状模式趋势，被认为是这种动态变化的强迫。与其他WBC相比，墨西哥湾流在全球变暖下预计会变弱，这很可能与大西洋子午线翻转环流(AMOC)的减弱有关。然而，我们也注意到，WBC的自然变化可能掩盖了现有观测数据集中全球变暖的长期影响，特别是在北半球。因此，长期观测或替代数据对于进一步评估WBCs的动态是必要的。
A significant increase in sea surface temperature (SST) is observed over the midlatitude western boundary currents (WBCs) during the past century. However, the mechanism for this phenomenon remains poorly understood due to limited observations. In the present paper, several coupled parameters (i.e., sea surface temperature (SST), ocean surface heat fluxes, ocean water velocity, ocean surface winds and sea level pressure (SLP)) are analyzed to identify the dynamic changes of the WBCs. Three types of independent data sets are used, including reanalysis products, satellite-blended observations. and climate model outputs from the fifth phase of the Climate Model Intercomparison Project (CMIP5). Based on these broad ranges of data, we find that the WBCs (except the Gulf Stream) are intensifying and shifting toward the poles as long-term effects of global warming. An intensification and poleward shift of near-surface ocean winds, attributed to positive annular mode-like trends, are proposed to be the forcing of such dynamic changes. In contrast to the other WBCs, the Gulf Stream is expected to be weaker under global warming, which is most likely related to a weakening of the Atlantic Meridional Overturning Circulation (AMOC). However, we also notice that the natural variations of WBCs might conceal the long-term effect of global warming in the available observational data sets, especially over the Northern Hemisphere. Therefore, long-term observations or proxy data are necessary to further evaluate the dynamics of the WBCs.