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The vertical structure of open-ocean submesoscale variability during a full seasonal cycle

The vertical structure of open-ocean submesoscale variability during a full seasonal cycle
The vertical structure of open-ocean submesoscale variability during a full seasonal cycle
Submesoscale dynamics are typically intensified at boundaries and assumed to weaken below the mixed layer in the open ocean. Here, we assess both the seasonality and the vertical distribution of submesoscale motions in an open-ocean region of the northeast Atlantic. Second-order structure functions, or variance in properties separated by distance, are calculated from submesoscale-resolving ocean glider and mooring observations, as well as a 1/48° numerical ocean model. This dataset combines a temporal coverage that extends through a full seasonal cycle, a horizontal resolution that captures spatial scales as small as 1 km, and vertical sampling that provides near-continuous coverage over the upper 1000 m. While kinetic and potential energies undergo a seasonal cycle, being largest during the winter, structure function slopes, influenced by dynamical characteristics, do not exhibit a strong seasonality. Furthermore, structure function slopes show weak vertical variations; there is not a strong change in properties across the base of the mixed layer. Additionally, we compare the observations to output from a high-resolution numerical model. The model does not represent variability associated with superinertial motions and does not capture an observed reduction in submesoscale kinetic energy that occurs throughout the water column in spring. Overall, these results suggest that the transfer of mixed layer submesoscale variability down to depths below the traditionally defined mixed layer is important throughout the weakly stratified subpolar mode waters.
0022-3670
145-160
Erickson, Zachary K.
6462fd11-b00d-4ddb-ab92-9d0f31bbb73e
Thompson, Andrew F.
1d1c0c88-2326-4ab3-8d7d-e874cbca99e6
Callies, Jörn
d7d71837-daff-4e61-955c-1f8e50bd3d67
Yu, Xiaolong
98f7de9e-94ea-4e7c-9890-487f0ca1a878
Garabato, Alberto Naveira
97c0e923-f076-4b38-b89b-938e11cea7a6
Klein, Patrice
e391cce8-4760-459c-a9e7-e9dfe36a8156
Erickson, Zachary K.
6462fd11-b00d-4ddb-ab92-9d0f31bbb73e
Thompson, Andrew F.
1d1c0c88-2326-4ab3-8d7d-e874cbca99e6
Callies, Jörn
d7d71837-daff-4e61-955c-1f8e50bd3d67
Yu, Xiaolong
98f7de9e-94ea-4e7c-9890-487f0ca1a878
Garabato, Alberto Naveira
97c0e923-f076-4b38-b89b-938e11cea7a6
Klein, Patrice
e391cce8-4760-459c-a9e7-e9dfe36a8156

Erickson, Zachary K., Thompson, Andrew F., Callies, Jörn, Yu, Xiaolong, Garabato, Alberto Naveira and Klein, Patrice (2020) The vertical structure of open-ocean submesoscale variability during a full seasonal cycle. Journal of Physical Oceanography, 50 (1), 145-160. (doi:10.1175/JPO-D-19-0030.1).

Record type: Article

Abstract

Submesoscale dynamics are typically intensified at boundaries and assumed to weaken below the mixed layer in the open ocean. Here, we assess both the seasonality and the vertical distribution of submesoscale motions in an open-ocean region of the northeast Atlantic. Second-order structure functions, or variance in properties separated by distance, are calculated from submesoscale-resolving ocean glider and mooring observations, as well as a 1/48° numerical ocean model. This dataset combines a temporal coverage that extends through a full seasonal cycle, a horizontal resolution that captures spatial scales as small as 1 km, and vertical sampling that provides near-continuous coverage over the upper 1000 m. While kinetic and potential energies undergo a seasonal cycle, being largest during the winter, structure function slopes, influenced by dynamical characteristics, do not exhibit a strong seasonality. Furthermore, structure function slopes show weak vertical variations; there is not a strong change in properties across the base of the mixed layer. Additionally, we compare the observations to output from a high-resolution numerical model. The model does not represent variability associated with superinertial motions and does not capture an observed reduction in submesoscale kinetic energy that occurs throughout the water column in spring. Overall, these results suggest that the transfer of mixed layer submesoscale variability down to depths below the traditionally defined mixed layer is important throughout the weakly stratified subpolar mode waters.

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Erickson_etal_JPO19_accepted - Accepted Manuscript
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e-pub ahead of print date: 10 January 2020
Published date: January 2020

Identifiers

Local EPrints ID: 437781
URI: http://eprints.soton.ac.uk/id/eprint/437781
ISSN: 0022-3670
PURE UUID: d5409640-28b5-43ee-8367-f67bc1030ad2

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Date deposited: 17 Feb 2020 17:30
Last modified: 10 Jul 2020 04:01

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