Preprints
https://doi.org/10.5194/egusphere-2022-1280
https://doi.org/10.5194/egusphere-2022-1280
 
25 Nov 2022
25 Nov 2022
Status: this preprint is open for discussion.

A numerical investigation on the energetics of a current along an ice-covered continental slope

Hengling Leng1, Hailun He1, and Michael A. Spall2 Hengling Leng et al.
  • 1State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China
  • 2Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

Abstract. The Chukchi Slope Current is a westward-flowing current along the Chukchi slope, which carries Pacific-origin water from the Chukchi shelf into the Canada Basin and helps set the regional hydrographic structure and ecosystem. Using a set of experiments with an idealized primitive equation numerical model, we investigate the energetics of the slope current during the ice-covered period. Numerical calculations show that the growth of surface eddies is suppressed by the ice friction, while perturbations at mid-depths can grow into eddies, consistent with linear instability analysis. However, because the ice stress is spatially variable, it is able to drive Ekman pumping to decrease the available potential energy (APE) and kinetic energy of both the mean flow and mesoscale eddies over a vertical scale of 100 m, well outside the frictional Ekman layer. The rate at which the APE changes is determined by the vertical buoyancy flux, which is negative as the ice-induced Ekman pumping advects lighter (denser) water upward (downward). A scaling analysis shows that Ekman pumping will dominate the release of APE for large scale flows, but the effect of baroclinic instability is also important when the horizontal scale of the mean flow is the baroclinic deformation radius and the eddy velocity is comparable to the mean flow velocity. Our numerical results highlight the importance of ice friction in the energetics of the slope current and eddies, and this may be relevant to other ice-covered regions.

Hengling Leng et al.

Status: open (until 20 Jan 2023)

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Hengling Leng et al.

Hengling Leng et al.

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Short summary
The Chukchi continental slope is one of the most energetic regions in the western Arctic Ocean as it is populated with strong boundary currents and mesoscale eddies. Using a set of experiments with an idealized primitive equation numerical model, we find that the ice friction can cause the loss of energy of both the Chukchi Slope Current and mesoscale eddies over a vertical scale of 100 m through Ekman pumping. Some scales for measuring the effects of ice friction are also provided.