Vertical Variations of Submesoscale Motions Between New Jersey Shelf and Bermuda

Jianing Li,Xin Wang

doi:10.3389/feart.2022.848916

Abstract

Based on the measurements from the Oleander Project, the behaviors of submesoscale motions are examined in the area between New Jersey Shelf and Bermuda. The vertical variation of Rossby number, the kinetic energy in the submesoscale range, and the power law of kinetic energy spectra suggest that submesoscale motions are mainly confined within the surface mixed layer with seasonality that is strong in winter and weak in summer. Besides, submesoscale motions with no significant seasonality were also found beneath the surface mixed layer, which could reach 500 m depth. A possible explanation is that the drastically varying flows in the Gulf Stream and mesoscale eddy periphery could generate strong lateral shear throughout their influence depth, which is favorable for breaking the geostrophic balance and causing submesoscale motions beneath the surface mixed layer.

Highlights

The ocean dynamics vary in a wide range of spatial–temporal scales
Submesoscale Motions Within the Mixed Layer Revealed by Rossby Number
All these results indicate the ubiquity of energetic submesoscale motions within the surface mixed layer in case 201512, which was conducted in winter

Summary

Introduction

The planetary scale motions, including large-scale and mesoscale motions, are dominated by planetary rotation and density stratification (Mensa et al, 2013). The kinetic energy reaching here would be dissipated into heat eventually (Kolmogorov et al, 1991); the microscale motions are the main energy sink for the ocean. Between these two scales, there are motions called submesoscale motions, with spatial scale ranging from O(100) m to O(10) km and in the form of fronts, filaments, and eddies (Thomas et al, 2008; McWilliams, 2016). Planetary rotation and advection are important, resulting in Ro ~ O(1), implying submesoscale motions are ageostrophic

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Discussion

Conclusion