Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary
Mesoscale eddies are ubiquitous dynamical features that tend to propagate westward and disappear along ocean western boundaries. Using a multiscale observational study, we assess the extent to which eddies dissipate via a direct cascade of energy at a western boundary. We analyze data from a ship‐ba...
Published in: | Journal of Geophysical Research: Oceans |
---|---|
Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2020
|
Subjects: | |
Online Access: | https://eprints.soton.ac.uk/445140/ https://eprints.soton.ac.uk/445140/1/2020JC016246.pdf |
id |
ftsouthampton:oai:eprints.soton.ac.uk:445140 |
---|---|
record_format |
openpolar |
spelling |
ftsouthampton:oai:eprints.soton.ac.uk:445140 2023-08-27T04:10:57+02:00 Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary Evans, Dafydd Gwyn Frajka‐williams, Eleanor Naveira Garabato, Alberto C. Polzin, Kurt L. Forryan, Alexander 2020-11-21 text https://eprints.soton.ac.uk/445140/ https://eprints.soton.ac.uk/445140/1/2020JC016246.pdf en English eng https://eprints.soton.ac.uk/445140/1/2020JC016246.pdf Evans, Dafydd Gwyn, Frajka‐williams, Eleanor, Naveira Garabato, Alberto C., Polzin, Kurt L. and Forryan, Alexander (2020) Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary. Journal of Geophysical Research: Oceans, 125 (11), [e2020JC016246]. (doi:10.1029/2020JC016246 <http://dx.doi.org/10.1029/2020JC016246>). cc_by_4 Article PeerReviewed 2020 ftsouthampton https://doi.org/10.1029/2020JC016246 2023-08-03T22:24:55Z Mesoscale eddies are ubiquitous dynamical features that tend to propagate westward and disappear along ocean western boundaries. Using a multiscale observational study, we assess the extent to which eddies dissipate via a direct cascade of energy at a western boundary. We analyze data from a ship‐based microstructure and velocity survey, and an 18‐month mooring deployment, to document the dissipation of energy in anticyclonic and cyclonic eddies impinging on the topographic slope east of the Bahamas, in the North Atlantic Ocean. These observations reveal high levels of turbulence where the steep and rough topographic slope modified the intensified northward flow associated with, in particular, anticyclonic eddies. Elevated dissipation was observed both near‐bottom and at mid depths (200–800 m). Near‐bottom turbulence occurred in the lee of a protruding escarpment, where elevated Froude numbers suggest hydraulic control. Energy was also radiated in the form of upward‐propagating internal waves. Elevated dissipation at mid depths occurred in regions of strong vertical shear, where the topographic slope modified the vertical structure of the northward eddy flow. Here, low Richardson numbers and a local change in the isopycnal gradient of potential vorticity (PV) suggest that the elevated dissipation was associated with horizontal shear instability. Elevated mid‐depth dissipation was also induced by topographic steering of the flow. This led to large anticyclonic vorticity and negative PV adjacent to the topographic slope, suggesting that centrifugal instability underpinned the local enhancement in dissipation. Our results provide a mechanistic benchmark for the realistic representation of eddy dissipation in ocean models. Article in Journal/Newspaper North Atlantic University of Southampton: e-Prints Soton Journal of Geophysical Research: Oceans 125 11 |
institution |
Open Polar |
collection |
University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
English |
description |
Mesoscale eddies are ubiquitous dynamical features that tend to propagate westward and disappear along ocean western boundaries. Using a multiscale observational study, we assess the extent to which eddies dissipate via a direct cascade of energy at a western boundary. We analyze data from a ship‐based microstructure and velocity survey, and an 18‐month mooring deployment, to document the dissipation of energy in anticyclonic and cyclonic eddies impinging on the topographic slope east of the Bahamas, in the North Atlantic Ocean. These observations reveal high levels of turbulence where the steep and rough topographic slope modified the intensified northward flow associated with, in particular, anticyclonic eddies. Elevated dissipation was observed both near‐bottom and at mid depths (200–800 m). Near‐bottom turbulence occurred in the lee of a protruding escarpment, where elevated Froude numbers suggest hydraulic control. Energy was also radiated in the form of upward‐propagating internal waves. Elevated dissipation at mid depths occurred in regions of strong vertical shear, where the topographic slope modified the vertical structure of the northward eddy flow. Here, low Richardson numbers and a local change in the isopycnal gradient of potential vorticity (PV) suggest that the elevated dissipation was associated with horizontal shear instability. Elevated mid‐depth dissipation was also induced by topographic steering of the flow. This led to large anticyclonic vorticity and negative PV adjacent to the topographic slope, suggesting that centrifugal instability underpinned the local enhancement in dissipation. Our results provide a mechanistic benchmark for the realistic representation of eddy dissipation in ocean models. |
format |
Article in Journal/Newspaper |
author |
Evans, Dafydd Gwyn Frajka‐williams, Eleanor Naveira Garabato, Alberto C. Polzin, Kurt L. Forryan, Alexander |
spellingShingle |
Evans, Dafydd Gwyn Frajka‐williams, Eleanor Naveira Garabato, Alberto C. Polzin, Kurt L. Forryan, Alexander Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
author_facet |
Evans, Dafydd Gwyn Frajka‐williams, Eleanor Naveira Garabato, Alberto C. Polzin, Kurt L. Forryan, Alexander |
author_sort |
Evans, Dafydd Gwyn |
title |
Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
title_short |
Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
title_full |
Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
title_fullStr |
Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
title_full_unstemmed |
Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
title_sort |
mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary |
publishDate |
2020 |
url |
https://eprints.soton.ac.uk/445140/ https://eprints.soton.ac.uk/445140/1/2020JC016246.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://eprints.soton.ac.uk/445140/1/2020JC016246.pdf Evans, Dafydd Gwyn, Frajka‐williams, Eleanor, Naveira Garabato, Alberto C., Polzin, Kurt L. and Forryan, Alexander (2020) Mesoscale eddy dissipation by a “zoo” of submesoscale processes at a western boundary. Journal of Geophysical Research: Oceans, 125 (11), [e2020JC016246]. (doi:10.1029/2020JC016246 <http://dx.doi.org/10.1029/2020JC016246>). |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.1029/2020JC016246 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
125 |
container_issue |
11 |
_version_ |
1775353362420596736 |