Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders
The importance of submesoscale instabilities, particularly mixed layer baroclinic instability and symmetric instability, on upper-ocean mixing and energetics is well documented in regions of strong, persistent fronts such as the Kuroshio and the Gulf Stream. Less attention has been devoted to studyi...
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ftuniveastangl:oai:ueaeprints.uea.ac.uk:57750 2023-05-15T17:41:37+02:00 Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders Thompson, Andrew Lazar, Ayah Buckingham, Christian Naveira Garabato, Alberto C. Damerell, Gillian Heywood, Karen 2016-04-05 application/pdf https://ueaeprints.uea.ac.uk/id/eprint/57750/ https://ueaeprints.uea.ac.uk/id/eprint/57750/4/JPO_D_15_0170.pdf https://doi.org/10.1175/JPO-D-15-0170.1 en eng https://ueaeprints.uea.ac.uk/id/eprint/57750/4/JPO_D_15_0170.pdf Thompson, Andrew, Lazar, Ayah, Buckingham, Christian, Naveira Garabato, Alberto C., Damerell, Gillian and Heywood, Karen (2016) Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders. Journal of Physical Oceanography, 46. 1285–1307. ISSN 0022-3670 doi:10.1175/JPO-D-15-0170.1 Article PeerReviewed 2016 ftuniveastangl https://doi.org/10.1175/JPO-D-15-0170.1 2023-03-23T23:32:12Z The importance of submesoscale instabilities, particularly mixed layer baroclinic instability and symmetric instability, on upper-ocean mixing and energetics is well documented in regions of strong, persistent fronts such as the Kuroshio and the Gulf Stream. Less attention has been devoted to studying submesoscale flows in the open ocean, far from long-term, mean geostrophic fronts, characteristic of a large proportion of the global ocean. This study presents a year-long, submesoscale-resolving time series of near-surface buoyancy gradients, potential vorticity, and instability characteristics, collected by ocean gliders, that provides insight into open-ocean submesoscale dynamics over a full annual cycle. The gliders continuously sampled a 225 km2 region in the subtropical northeast Atlantic, measuring temperature, salinity, and pressure along 292 short (~20 km) hydrographic sections. Glider observations show a seasonal cycle in near-surface stratification. Throughout the fall (September–November), the mixed layer deepens, predominantly through gravitational instability, indicating that surface cooling dominates submesoscale restratification processes. During winter (December–March), mixed layer depths are more variable, and estimates of the balanced Richardson number, which measures the relative importance of lateral and vertical buoyancy gradients, depict conditions favorable to symmetric instability. The importance of mixed layer instabilities on the restratification of the mixed layer, as compared with surface heating and cooling, shows that submesoscale processes can reverse the sign of an equivalent heat flux up to 25% of the time during winter. These results demonstrate that the open-ocean mixed layer hosts various forced and unforced instabilities, which become more prevalent during winter, and emphasize that accurate parameterizations of submesoscale processes are needed throughout the ocean. Article in Journal/Newspaper Northeast Atlantic University of East Anglia: UEA Digital Repository Journal of Physical Oceanography 46 4 1285 1307 |
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Open Polar |
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University of East Anglia: UEA Digital Repository |
op_collection_id |
ftuniveastangl |
language |
English |
description |
The importance of submesoscale instabilities, particularly mixed layer baroclinic instability and symmetric instability, on upper-ocean mixing and energetics is well documented in regions of strong, persistent fronts such as the Kuroshio and the Gulf Stream. Less attention has been devoted to studying submesoscale flows in the open ocean, far from long-term, mean geostrophic fronts, characteristic of a large proportion of the global ocean. This study presents a year-long, submesoscale-resolving time series of near-surface buoyancy gradients, potential vorticity, and instability characteristics, collected by ocean gliders, that provides insight into open-ocean submesoscale dynamics over a full annual cycle. The gliders continuously sampled a 225 km2 region in the subtropical northeast Atlantic, measuring temperature, salinity, and pressure along 292 short (~20 km) hydrographic sections. Glider observations show a seasonal cycle in near-surface stratification. Throughout the fall (September–November), the mixed layer deepens, predominantly through gravitational instability, indicating that surface cooling dominates submesoscale restratification processes. During winter (December–March), mixed layer depths are more variable, and estimates of the balanced Richardson number, which measures the relative importance of lateral and vertical buoyancy gradients, depict conditions favorable to symmetric instability. The importance of mixed layer instabilities on the restratification of the mixed layer, as compared with surface heating and cooling, shows that submesoscale processes can reverse the sign of an equivalent heat flux up to 25% of the time during winter. These results demonstrate that the open-ocean mixed layer hosts various forced and unforced instabilities, which become more prevalent during winter, and emphasize that accurate parameterizations of submesoscale processes are needed throughout the ocean. |
format |
Article in Journal/Newspaper |
author |
Thompson, Andrew Lazar, Ayah Buckingham, Christian Naveira Garabato, Alberto C. Damerell, Gillian Heywood, Karen |
spellingShingle |
Thompson, Andrew Lazar, Ayah Buckingham, Christian Naveira Garabato, Alberto C. Damerell, Gillian Heywood, Karen Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
author_facet |
Thompson, Andrew Lazar, Ayah Buckingham, Christian Naveira Garabato, Alberto C. Damerell, Gillian Heywood, Karen |
author_sort |
Thompson, Andrew |
title |
Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
title_short |
Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
title_full |
Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
title_fullStr |
Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
title_full_unstemmed |
Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders |
title_sort |
open-ocean submesoscale motions: a full seasonal cycle of mixed layer instabilities from gliders |
publishDate |
2016 |
url |
https://ueaeprints.uea.ac.uk/id/eprint/57750/ https://ueaeprints.uea.ac.uk/id/eprint/57750/4/JPO_D_15_0170.pdf https://doi.org/10.1175/JPO-D-15-0170.1 |
genre |
Northeast Atlantic |
genre_facet |
Northeast Atlantic |
op_relation |
https://ueaeprints.uea.ac.uk/id/eprint/57750/4/JPO_D_15_0170.pdf Thompson, Andrew, Lazar, Ayah, Buckingham, Christian, Naveira Garabato, Alberto C., Damerell, Gillian and Heywood, Karen (2016) Open-ocean submesoscale motions: A full seasonal cycle of mixed layer instabilities from gliders. Journal of Physical Oceanography, 46. 1285–1307. ISSN 0022-3670 doi:10.1175/JPO-D-15-0170.1 |
op_doi |
https://doi.org/10.1175/JPO-D-15-0170.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
46 |
container_issue |
4 |
container_start_page |
1285 |
op_container_end_page |
1307 |
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1766143268509188096 |