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Energetic Submesoscales Maintain Strong Mixed Layer Stratification during an Autumn Storm

Published version
Peer-reviewed

Type

Article

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Authors

Whitt, DB 
Taylor, JR 

Abstract

Atmospheric storms are an important driver of changes in upper-ocean stratification and small-scale (1-100 m) turbulence. Yet, the modifying effects of submesoscale (0.1-10 km) motions in the ocean mixed layer on stratification and small-scale turbulence during a storm are not well understood. Here, we use large-eddy simulations to study the coupled response of submesocales and small-scale turbulence to the passage of an idealized autumn storm, with a wind stress representative of a storm observed in the North Atlantic above the Porcupine Abyssal Plain. Due to a relatively shallow mixed layer and a strong down-front wind, existing scaling theory predicts that submesoscales should be unable to re-stratify the mixed layer during the storm. In contrast, our simulations reveal a persistent and strong mean stratification in the mixed layer both during and after the storm. In addition, we find that the mean dissipation rate remains elevated throughout the mixed layer during the storm, despite the strong mean stratification. These results are attributed to strong spatial variability in stratification and small-scale turbulence at the submesoscale and have important implications for sampling and modeling submesoscales and their effects on stratification and turbulence in the upper-ocean.

Description

Keywords

eddies, oceanic mixed layer, severe storms, large eddy simulations

Journal Title

Journal of Physical Oceanography

Conference Name

Journal ISSN

0022-3670
1520-0485

Volume Title

47

Publisher

American Meteorological Society
Sponsorship
Natural Environment Research Council (NE/J010472/1)
DBW was supported by the National Science Foundation via an NSF Postdoctoral Fellowship (1421125) and an NSF Polar Programs Grant (1501993). JRT was supported by the Natural Environment Research Council via Award NE/J010472/1.
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