Temporal variability of diapycnal mixing in Shag Rocks Passage
Diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability, but the temporal variability has been little studied. Here we present results from a method developed to calculate diapycnal diffusivity from moored Acoustic Doppler Current Profiler (ADCP) velocity she...
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2012
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ftuniveastangl:oai:ueaeprints.uea.ac.uk:36934 2023-05-15T18:25:58+02:00 Temporal variability of diapycnal mixing in Shag Rocks Passage Damerell, Gillian M. Heywood, Karen J. Stevens, David P. Naveira Garabato, Alberto C. 2012 application/pdf https://ueaeprints.uea.ac.uk/id/eprint/36934/ https://ueaeprints.uea.ac.uk/id/eprint/36934/1/DS_58.pdf https://doi.org/10.1175/2011JPO4573.1 en eng https://ueaeprints.uea.ac.uk/id/eprint/36934/1/DS_58.pdf Damerell, Gillian M., Heywood, Karen J., Stevens, David P. and Naveira Garabato, Alberto C. (2012) Temporal variability of diapycnal mixing in Shag Rocks Passage. Journal of Physical Oceanography, 42 (3). pp. 370-385. ISSN 0022-3670 doi:10.1175/2011JPO4573.1 Article PeerReviewed 2012 ftuniveastangl https://doi.org/10.1175/2011JPO4573.1 2023-01-30T21:32:48Z Diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability, but the temporal variability has been little studied. Here we present results from a method developed to calculate diapycnal diffusivity from moored Acoustic Doppler Current Profiler (ADCP) velocity shear profiles. An 18-month time series of diffusivity is presented from data taken by a LongRanger ADCP moored at 2400 m depth, 600 m above the sea floor, in Shag Rocks Passage, a deep passage in the North Scotia Ridge (Southern Ocean). The Polar Front is constrained to pass through this passage, and the strong currents and complex topography are expected to result in enhanced mixing. The spatial distribution of diffusivity in Shag Rocks Passage deduced from lowered ADCP shear is consistent with published values for similar regions, with diffusivity possibly as large as 90 × 10-4 m2 s-1 near the sea floor, decreasing to the expected background level of ~ 0.1 × 10-4 m2 s-1 in areas away from topography. The moored ADCP profiles spanned a depth range of 2400 to 1800 m; thus the moored time series was obtained from a region of moderately enhanced diffusivity. The diffusivity time series has a median of 3.3 × 10-4 m2 s-1 and a range of 0.5 × 10-4 m2 s-1 to 57 × 10-4 m2 s-1. There is no significant signal at annual or semiannual periods, but there is evidence of signals at periods of approximately fourteen days (likely due to the spring-neaps tidal cycle), and at periods of 3.8 and 2.6 days most likely due to topographically-trapped waves propagating around the local seamount. Using the observed stratification and an axisymmetric seamount, of similar dimensions to the one west of the mooring, in a model of baroclinic topographically-trapped waves, produces periods of 3.8 and 2.6 days, in agreement with the signals observed. The diffusivity is anti-correlated with the rotary coefficient (indicating that stronger mixing occurs during times of upward energy propagation), which suggests that mixing occurs due to the breaking of ... Article in Journal/Newspaper Southern Ocean University of East Anglia: UEA Digital Repository Deep Passage ENVELOPE(-68.014,-68.014,63.467,63.467) North Scotia Ridge ENVELOPE(-51.431,-51.431,-53.581,-53.581) Shag Rocks ENVELOPE(-42.033,-42.033,-53.550,-53.550) Southern Ocean Journal of Physical Oceanography 42 3 370 385 |
institution |
Open Polar |
collection |
University of East Anglia: UEA Digital Repository |
op_collection_id |
ftuniveastangl |
language |
English |
description |
Diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability, but the temporal variability has been little studied. Here we present results from a method developed to calculate diapycnal diffusivity from moored Acoustic Doppler Current Profiler (ADCP) velocity shear profiles. An 18-month time series of diffusivity is presented from data taken by a LongRanger ADCP moored at 2400 m depth, 600 m above the sea floor, in Shag Rocks Passage, a deep passage in the North Scotia Ridge (Southern Ocean). The Polar Front is constrained to pass through this passage, and the strong currents and complex topography are expected to result in enhanced mixing. The spatial distribution of diffusivity in Shag Rocks Passage deduced from lowered ADCP shear is consistent with published values for similar regions, with diffusivity possibly as large as 90 × 10-4 m2 s-1 near the sea floor, decreasing to the expected background level of ~ 0.1 × 10-4 m2 s-1 in areas away from topography. The moored ADCP profiles spanned a depth range of 2400 to 1800 m; thus the moored time series was obtained from a region of moderately enhanced diffusivity. The diffusivity time series has a median of 3.3 × 10-4 m2 s-1 and a range of 0.5 × 10-4 m2 s-1 to 57 × 10-4 m2 s-1. There is no significant signal at annual or semiannual periods, but there is evidence of signals at periods of approximately fourteen days (likely due to the spring-neaps tidal cycle), and at periods of 3.8 and 2.6 days most likely due to topographically-trapped waves propagating around the local seamount. Using the observed stratification and an axisymmetric seamount, of similar dimensions to the one west of the mooring, in a model of baroclinic topographically-trapped waves, produces periods of 3.8 and 2.6 days, in agreement with the signals observed. The diffusivity is anti-correlated with the rotary coefficient (indicating that stronger mixing occurs during times of upward energy propagation), which suggests that mixing occurs due to the breaking of ... |
format |
Article in Journal/Newspaper |
author |
Damerell, Gillian M. Heywood, Karen J. Stevens, David P. Naveira Garabato, Alberto C. |
spellingShingle |
Damerell, Gillian M. Heywood, Karen J. Stevens, David P. Naveira Garabato, Alberto C. Temporal variability of diapycnal mixing in Shag Rocks Passage |
author_facet |
Damerell, Gillian M. Heywood, Karen J. Stevens, David P. Naveira Garabato, Alberto C. |
author_sort |
Damerell, Gillian M. |
title |
Temporal variability of diapycnal mixing in Shag Rocks Passage |
title_short |
Temporal variability of diapycnal mixing in Shag Rocks Passage |
title_full |
Temporal variability of diapycnal mixing in Shag Rocks Passage |
title_fullStr |
Temporal variability of diapycnal mixing in Shag Rocks Passage |
title_full_unstemmed |
Temporal variability of diapycnal mixing in Shag Rocks Passage |
title_sort |
temporal variability of diapycnal mixing in shag rocks passage |
publishDate |
2012 |
url |
https://ueaeprints.uea.ac.uk/id/eprint/36934/ https://ueaeprints.uea.ac.uk/id/eprint/36934/1/DS_58.pdf https://doi.org/10.1175/2011JPO4573.1 |
long_lat |
ENVELOPE(-68.014,-68.014,63.467,63.467) ENVELOPE(-51.431,-51.431,-53.581,-53.581) ENVELOPE(-42.033,-42.033,-53.550,-53.550) |
geographic |
Deep Passage North Scotia Ridge Shag Rocks Southern Ocean |
geographic_facet |
Deep Passage North Scotia Ridge Shag Rocks Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://ueaeprints.uea.ac.uk/id/eprint/36934/1/DS_58.pdf Damerell, Gillian M., Heywood, Karen J., Stevens, David P. and Naveira Garabato, Alberto C. (2012) Temporal variability of diapycnal mixing in Shag Rocks Passage. Journal of Physical Oceanography, 42 (3). pp. 370-385. ISSN 0022-3670 doi:10.1175/2011JPO4573.1 |
op_doi |
https://doi.org/10.1175/2011JPO4573.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
42 |
container_issue |
3 |
container_start_page |
370 |
op_container_end_page |
385 |
_version_ |
1766207720806940672 |