Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean
We test the use of a measure to diagnose a sub-mesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities. Specifically, the robustness of a ‘roughness’ measure to discriminate between tracer fields experienci...
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American Meteorological Society
2015
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Online Access: | http://nora.nerc.ac.uk/id/eprint/504873/ https://nora.nerc.ac.uk/id/eprint/504873/1/JPO-D-14-0047.pdf |
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ftnerc:oai:nora.nerc.ac.uk:504873 2023-05-15T16:02:33+02:00 Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean Boland, Emma J.D. Shuckburgh, Emily Haynes, Peter H. Ledwell, James R. Messias, Marie-José Watson, Andrew J. 2015-06-01 text http://nora.nerc.ac.uk/id/eprint/504873/ https://nora.nerc.ac.uk/id/eprint/504873/1/JPO-D-14-0047.pdf en eng American Meteorological Society https://nora.nerc.ac.uk/id/eprint/504873/1/JPO-D-14-0047.pdf Boland, Emma J.D. orcid:0000-0003-2430-7763 Shuckburgh, Emily orcid:0000-0001-9206-3444 Haynes, Peter H.; Ledwell, James R.; Messias, Marie-José; Watson, Andrew J. 2015 Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean. Journal of Physical Oceanography, 45 (6). 1610-1631. https://doi.org/10.1175/JPO-D-14-0047.1 <https://doi.org/10.1175/JPO-D-14-0047.1> Publication - Article PeerReviewed 2015 ftnerc https://doi.org/10.1175/JPO-D-14-0047.1 2023-02-04T19:38:38Z We test the use of a measure to diagnose a sub-mesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities. Specifically, the robustness of a ‘roughness’ measure to discriminate between tracer fields experiencing different sub-mesoscale isopycnal diffusivities and advected by scaled altimetric velocity fields is investigated. We use the measure to compare numerical simulations of the tracer released at a depth of about 1.5 km in the Pacific sector of the Southern Ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field campaign with observations of the tracer taken on DIMES cruises. We find that simulations with an isopycnal diffusivity of ~20 m2s−1 best match observations in the Pacific sector of the ACC, rising to ~20-50 m2s−1 through Drake Passage, representing sub-mesoscale processes and any mesoscale processes unresolved by the advecting altimetry fields. The roughness measure is demonstrated to be a statistically robust way to estimate a small-scale diffusivity when measurements are relatively sparse in space and time, although it does not work if there are too few measurements overall. The planning of tracer measurements during a cruise in order to maximise the robustness of the roughness measure is also considered. It is found that the robustness is increased if the spatial resolution of tracer measurements is increased with the time since tracer release. Article in Journal/Newspaper Drake Passage Southern Ocean Natural Environment Research Council: NERC Open Research Archive Southern Ocean Drake Passage Pacific Journal of Physical Oceanography 45 6 1610 1631 |
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Open Polar |
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Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
We test the use of a measure to diagnose a sub-mesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities. Specifically, the robustness of a ‘roughness’ measure to discriminate between tracer fields experiencing different sub-mesoscale isopycnal diffusivities and advected by scaled altimetric velocity fields is investigated. We use the measure to compare numerical simulations of the tracer released at a depth of about 1.5 km in the Pacific sector of the Southern Ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field campaign with observations of the tracer taken on DIMES cruises. We find that simulations with an isopycnal diffusivity of ~20 m2s−1 best match observations in the Pacific sector of the ACC, rising to ~20-50 m2s−1 through Drake Passage, representing sub-mesoscale processes and any mesoscale processes unresolved by the advecting altimetry fields. The roughness measure is demonstrated to be a statistically robust way to estimate a small-scale diffusivity when measurements are relatively sparse in space and time, although it does not work if there are too few measurements overall. The planning of tracer measurements during a cruise in order to maximise the robustness of the roughness measure is also considered. It is found that the robustness is increased if the spatial resolution of tracer measurements is increased with the time since tracer release. |
format |
Article in Journal/Newspaper |
author |
Boland, Emma J.D. Shuckburgh, Emily Haynes, Peter H. Ledwell, James R. Messias, Marie-José Watson, Andrew J. |
spellingShingle |
Boland, Emma J.D. Shuckburgh, Emily Haynes, Peter H. Ledwell, James R. Messias, Marie-José Watson, Andrew J. Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
author_facet |
Boland, Emma J.D. Shuckburgh, Emily Haynes, Peter H. Ledwell, James R. Messias, Marie-José Watson, Andrew J. |
author_sort |
Boland, Emma J.D. |
title |
Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
title_short |
Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
title_full |
Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
title_fullStr |
Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
title_full_unstemmed |
Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean |
title_sort |
estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the southern ocean |
publisher |
American Meteorological Society |
publishDate |
2015 |
url |
http://nora.nerc.ac.uk/id/eprint/504873/ https://nora.nerc.ac.uk/id/eprint/504873/1/JPO-D-14-0047.pdf |
geographic |
Southern Ocean Drake Passage Pacific |
geographic_facet |
Southern Ocean Drake Passage Pacific |
genre |
Drake Passage Southern Ocean |
genre_facet |
Drake Passage Southern Ocean |
op_relation |
https://nora.nerc.ac.uk/id/eprint/504873/1/JPO-D-14-0047.pdf Boland, Emma J.D. orcid:0000-0003-2430-7763 Shuckburgh, Emily orcid:0000-0001-9206-3444 Haynes, Peter H.; Ledwell, James R.; Messias, Marie-José; Watson, Andrew J. 2015 Estimating a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean. Journal of Physical Oceanography, 45 (6). 1610-1631. https://doi.org/10.1175/JPO-D-14-0047.1 <https://doi.org/10.1175/JPO-D-14-0047.1> |
op_doi |
https://doi.org/10.1175/JPO-D-14-0047.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
45 |
container_issue |
6 |
container_start_page |
1610 |
op_container_end_page |
1631 |
_version_ |
1766398218606739456 |