Aspect Ratio of Eddies Inferred From Argo Floats and Satellite Altimeter Data in the Ocean

作者：Liu, ZhiYing; Liao, GuangHong^*; Hu, XiaoKai; Zhou, BeiFeng

来源：JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 2020, 125(1): e2019JC015555.

DOI：10.1029/2019JC015555

• UNIVERSAL ASPECT RATIO
• MESOSCALE EDDIES
• VERTICAL STRUCTURE
• INTERNAL WAVES
• VARIABILITY
• EVOLUTION
• VORTICES

Mesoscale eddies dominate the majority of oceanic kinetic energy. The size of eddies is one of the basic properties; however, little is known about it because of lack of observations. Especially, their global vertical extent has still not been well investigated. Here, a ratio relationship of height to length scale for an eddy is derived based on dynamical constraints. Global satellite altimetry data combined with Argo float observations are used to calculate the aspect ratios of mesoscale eddies in the global ocean, and then their vertical scale is inferred. Approximately 25% of the total identified eddies with lifetimes >= 16 weeks from January 2002 to December 2017 trapped at least an Argo float near the eddy center. The result shows that the size of eddies has an obvious latitudinal dependence. Eddies at middle-low latitudes tend to be "large and shallow" with small aspect ratios, and eddies at high latitudes tend to be "small and deep-reaching" with large aspect ratios. Such results are coarsely considered as a competition between rotation and stratification. Eddy aspect ratios in middle-high-latitude regions show enhanced variance compared to those in low-latitude regions. More than half of eddies have a vertical extent smaller than 400 m. The majority of eddies extend over the mixed layer depth and are instead situated in the pycnocline. Some eddies at the middle-high latitudes penetrate through the entire pycnocline and reach deep ocean; as such, these eddies may play an important role in linking the deep-sea circulations and the surface circulations.

• 单位
  河海大学; 国家海洋局第二海洋研究所; 卫星海洋环境动力学国家重点实验室