The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities
The evolution of upper-ocean potential vorticity (PV) over a full year in a typical midocean area of the northeast Atlantic is examined using submesoscale- and mesoscale-resolving hydrographic and velocity measurements from a mooring array. A PV budget framework is applied to quantitatively document...
Published in: | Journal of Physical Oceanography |
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2021
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Online Access: | https://eprints.soton.ac.uk/447456/ https://eprints.soton.ac.uk/447456/1/JPO_PV_budget_accepted_version_20201113.pdf https://eprints.soton.ac.uk/447456/2/_15200485_Journal_of_Physical_Oceanography_The_Annual_Cycle_of_Upper_Ocean_Potential_Vorticity_and_Its_Relationship_to_Submesoscale_Instabilities.pdf |
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ftsouthampton:oai:eprints.soton.ac.uk:447456 2023-12-03T10:27:42+01:00 The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities Yu, Xiaolong Naveira Garabato, Alberto Martin, Adrian Marshall, David P. 2021-02 text https://eprints.soton.ac.uk/447456/ https://eprints.soton.ac.uk/447456/1/JPO_PV_budget_accepted_version_20201113.pdf https://eprints.soton.ac.uk/447456/2/_15200485_Journal_of_Physical_Oceanography_The_Annual_Cycle_of_Upper_Ocean_Potential_Vorticity_and_Its_Relationship_to_Submesoscale_Instabilities.pdf en English eng https://eprints.soton.ac.uk/447456/1/JPO_PV_budget_accepted_version_20201113.pdf https://eprints.soton.ac.uk/447456/2/_15200485_Journal_of_Physical_Oceanography_The_Annual_Cycle_of_Upper_Ocean_Potential_Vorticity_and_Its_Relationship_to_Submesoscale_Instabilities.pdf Yu, Xiaolong, Naveira Garabato, Alberto, Martin, Adrian and Marshall, David P. (2021) The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities. Journal of Physical Oceanography, 51 (2), 385-402. (doi:10.1175/JPO-D-20-0099.1 <http://dx.doi.org/10.1175/JPO-D-20-0099.1>). cc_by_4 Article PeerReviewed 2021 ftsouthampton https://doi.org/10.1175/JPO-D-20-0099.1 2023-11-03T00:00:46Z The evolution of upper-ocean potential vorticity (PV) over a full year in a typical midocean area of the northeast Atlantic is examined using submesoscale- and mesoscale-resolving hydrographic and velocity measurements from a mooring array. A PV budget framework is applied to quantitatively document the competing physical processes responsible for deepening and shoaling the mixed layer. The observations reveal a distinct seasonal cycle in upper-ocean PV, characterized by frequent occurrences of negative PV within deep (up to about 350 m) mixed layers from winter to mid-spring, and positive PV beneath shallow (mostly less than 50 m) mixed layers during the remainder of the year. The cumulative positive and negative subinertial changes in the mixed layer depth, which are largely unaccounted for by advective contributions, exceed the deepest mixed layer by one order of magnitude, suggesting that mixed layer depth is shaped by the competing effects of destratifying and restratifying processes. Deep mixed layers are attributed to persistent atmospheric cooling from winter to mid-spring, which triggers gravitational instability leading to mixed layer deepening. However, on shorter time scales of days, conditions favorable to symmetric instability often occur as winds intermittently align with transient frontal flows. The ensuing submesoscale frontal instabilities are found to fundamentally alter upper-ocean turbulent convection, and limit the deepening of the mixed layer in the winter-to-mid-spring period. These results emphasize the key role of submesoscale frontal instabilities in determining the seasonal evolution of the mixed layer in the open ocean. Article in Journal/Newspaper Northeast Atlantic University of Southampton: e-Prints Soton Journal of Physical Oceanography 51 2 385 402 |
institution |
Open Polar |
collection |
University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
English |
description |
The evolution of upper-ocean potential vorticity (PV) over a full year in a typical midocean area of the northeast Atlantic is examined using submesoscale- and mesoscale-resolving hydrographic and velocity measurements from a mooring array. A PV budget framework is applied to quantitatively document the competing physical processes responsible for deepening and shoaling the mixed layer. The observations reveal a distinct seasonal cycle in upper-ocean PV, characterized by frequent occurrences of negative PV within deep (up to about 350 m) mixed layers from winter to mid-spring, and positive PV beneath shallow (mostly less than 50 m) mixed layers during the remainder of the year. The cumulative positive and negative subinertial changes in the mixed layer depth, which are largely unaccounted for by advective contributions, exceed the deepest mixed layer by one order of magnitude, suggesting that mixed layer depth is shaped by the competing effects of destratifying and restratifying processes. Deep mixed layers are attributed to persistent atmospheric cooling from winter to mid-spring, which triggers gravitational instability leading to mixed layer deepening. However, on shorter time scales of days, conditions favorable to symmetric instability often occur as winds intermittently align with transient frontal flows. The ensuing submesoscale frontal instabilities are found to fundamentally alter upper-ocean turbulent convection, and limit the deepening of the mixed layer in the winter-to-mid-spring period. These results emphasize the key role of submesoscale frontal instabilities in determining the seasonal evolution of the mixed layer in the open ocean. |
format |
Article in Journal/Newspaper |
author |
Yu, Xiaolong Naveira Garabato, Alberto Martin, Adrian Marshall, David P. |
spellingShingle |
Yu, Xiaolong Naveira Garabato, Alberto Martin, Adrian Marshall, David P. The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
author_facet |
Yu, Xiaolong Naveira Garabato, Alberto Martin, Adrian Marshall, David P. |
author_sort |
Yu, Xiaolong |
title |
The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
title_short |
The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
title_full |
The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
title_fullStr |
The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
title_full_unstemmed |
The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
title_sort |
annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities |
publishDate |
2021 |
url |
https://eprints.soton.ac.uk/447456/ https://eprints.soton.ac.uk/447456/1/JPO_PV_budget_accepted_version_20201113.pdf https://eprints.soton.ac.uk/447456/2/_15200485_Journal_of_Physical_Oceanography_The_Annual_Cycle_of_Upper_Ocean_Potential_Vorticity_and_Its_Relationship_to_Submesoscale_Instabilities.pdf |
genre |
Northeast Atlantic |
genre_facet |
Northeast Atlantic |
op_relation |
https://eprints.soton.ac.uk/447456/1/JPO_PV_budget_accepted_version_20201113.pdf https://eprints.soton.ac.uk/447456/2/_15200485_Journal_of_Physical_Oceanography_The_Annual_Cycle_of_Upper_Ocean_Potential_Vorticity_and_Its_Relationship_to_Submesoscale_Instabilities.pdf Yu, Xiaolong, Naveira Garabato, Alberto, Martin, Adrian and Marshall, David P. (2021) The annual cycle of upper-ocean potential vorticity and its relationship to submesoscale instabilities. Journal of Physical Oceanography, 51 (2), 385-402. (doi:10.1175/JPO-D-20-0099.1 <http://dx.doi.org/10.1175/JPO-D-20-0099.1>). |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.1175/JPO-D-20-0099.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
51 |
container_issue |
2 |
container_start_page |
385 |
op_container_end_page |
402 |
_version_ |
1784277554529566720 |