气候变暖下全球大洋大、中尺度过程变化

Changes of the Global Oceanic Large-scale and Mesoscale Processes under GlobalWarming

【目的】研究大尺度海洋运动以及中尺度海洋过程受气候变暖影响所产生的变化。【方法】通过计算全球绝对动力高度(ADT)的方差确定海平面在1993-2014年振荡幅度的变化。【结果和结论】ADT方差的增加趋势表明全球海洋的波动和地转流的增强。将全球绝对动力高度(ADT)分为两个不同部分:全球3 a平均海表面高度(MSS)和残余绝对动力高度(RADT),以确定不断增加的波动在何种尺度上占主导地位。在全球变暖大背景下这两部分表现出不同的变化趋势。MSS方差的增加可归因于全球海平面的不均匀上升和太平洋海洋环流的增强,而RADT方差变化趋势接近于0,这表明海洋中尺度信号无明显增强或减弱。通过引入信息熵以及对全球ADT分布的研究,发现全球ADT呈类高斯分布,信息熵的增加趋势表明极端海平面的出现频率增加。

【Objective】To study global change of large-scale and mesoscale processes under global warming.【Method】ADT(absolute dynamic topography)Variance has been calculated to determine the magnitude of the sea level variation during two decades(from 1993 to 2014).【Result and Conclusion】Increasing trend of variance of ADT indicates the global oceanic fluctuation and geostrophic flow are intensified.To further determine the scale on which the increasing fluctuation dominates,the global ADT has been separated into two distinguished parts:the global three-year mean sea surface(MSS)and the residual absolute dynamic topography(RADT).Those two parts exhibit different variations.Increased variance of MSS can be ascribed to the non-uniform rising of global sea level and an enhancement of ocean gyres in the Pacific Ocean.While trend in the variance of RADT is found to be close to zero,which suggests an unchanged ocean mesoscale variability.Finally,by introducing the information entropy and analyzing the global ADT distributions,this study found a Gaussian-like distribution of global ADT,and increasing trend of information entropy means more frequent appearance of extreme sea level.