Abstract
In areas with rough bathymetry, the vertical structure of ocean eddies can be decomposed into “surface modes,” which are surface intensified, and exhibit a velocity of nearly zero at the bottom . Furthermore, ocean surface modes are ubiquitous. Atlases of the first surface mode (SM1) deformation radius were computed on a global \(0.25 \times 0.25^{^\circ }\) grid using WOA2013 and the data from Generalized Digital Environment Model (GDEM). Monthly and seasonal changes were also analyzed. The annual average SM1 deformation radius was approximately 1.5 times larger than the Rossby radius of deformation; the main difference occurred in areas with rough bathymetry, including continental margins and mid-ocean ridges. The seasonal and monthly average SM1 deformation radius shows an evident annual cycle.
Highlights
Oceanography has developed rapidly since the appearance of satellites, which provide a means to observe the global ocean surface
Gridded sea surface height (SSH) data are available with a spatial resolution of 0.25° and a daily temporal scale
We can obtain traditional baroclinic modes; with steep or rough bathymetry, the solution will be another set of orthogonal basis functions “surface modes.”
Summary
Oceanography has developed rapidly since the appearance of satellites, which provide a means to observe the global ocean surface. We can obtain traditional baroclinic modes; with steep or rough bathymetry, the solution will be another set of orthogonal basis functions “surface modes.”. These modes are surface intensified with a velocity of nearly zero at the bottom. LaCase (2017) demonstrated that with realistic bathymetry and/or bottom friction, surface modes are ubiquitous in the ocean This would explain the EOF1 of Wunsch (1997) and de La Lama et al (2016) in many extratropical regions. Its global distribution is given and compared with that of the Rossby deformation radius
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