An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean
Finescale estimates of diapycnal diffusivity κ are computed from CTD and expendable CTD (XCTD) data sampled in Drake Passage and in the eastern Pacific sector of the Southern Ocean and are compared against microstructure measurements from the same times and locations. The microstructure data show ve...
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ftcdlib:oai:escholarship.org:ark:/13030/qt3ns2x13q 2024-09-15T18:03:56+00:00 An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean Frants, Marina Damerell, Gillian M Gille, Sarah T Heywood, Karen J MacKinnon, Jennifer Sprintall, Janet 2647 - 2661 2013-11-01 application/pdf https://escholarship.org/uc/item/3ns2x13q https://escholarship.org/content/qt3ns2x13q/qt3ns2x13q.pdf https://doi.org/10.1175/jtech-d-12-00241.1 unknown eScholarship, University of California qt3ns2x13q https://escholarship.org/uc/item/3ns2x13q https://escholarship.org/content/qt3ns2x13q/qt3ns2x13q.pdf doi:10.1175/jtech-d-12-00241.1 public Journal of Atmospheric and Oceanic Technology, vol 30, iss 11 Diapycnal mixing Mixing In situ oceanic observations Ship observations Atmospheric Sciences Oceanography Maritime Engineering Meteorology & Atmospheric Sciences article 2013 ftcdlib https://doi.org/10.1175/jtech-d-12-00241.1 2024-06-28T06:28:20Z Finescale estimates of diapycnal diffusivity κ are computed from CTD and expendable CTD (XCTD) data sampled in Drake Passage and in the eastern Pacific sector of the Southern Ocean and are compared against microstructure measurements from the same times and locations. The microstructure data show vertical diffusivities that are one-third to one-fifth as large over the smooth abyssal plain in the southeastern Pacific as they are in Drake Passage, where diffusivities are thought to be enhanced by the flow of theAntarctic CircumpolarCurrent over rough topography. Finescalemethods based on vertical strain estimates are successful at capturing the spatial variability between the low-mixing regime in the southeastern Pacific and the high-mixing regime of Drake Passage. Thorpe-scale estimates for the same dataset fail to capture the differences between Drake Passage and eastern Pacific estimates. XCTD profiles have lower vertical resolution and higher noise levels after filtering than CTD profiles, resulting in XCTD κ estimates that are, on average, an order of magnitude higher than CTD estimates. Overall, microstructure diffusivity estimates are better matched by strain-based estimates than by estimates based on Thorpe scales, and CTD data appear to perform better than XCTD data. However, even the CTD-based strain diffusivity estimates can differ from microstructure diffusivities by nearly an order of magnitude, suggesting that density-based fine-structure methods of estimating mixing from CTD or XCTD data have real limitations in low-stratification regimes such as the Southern Ocean. © 2013 American Meteorological Society. Article in Journal/Newspaper Drake Passage Southern Ocean University of California: eScholarship Journal of Atmospheric and Oceanic Technology 30 11 2647 2661 |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Diapycnal mixing Mixing In situ oceanic observations Ship observations Atmospheric Sciences Oceanography Maritime Engineering Meteorology & Atmospheric Sciences |
spellingShingle |
Diapycnal mixing Mixing In situ oceanic observations Ship observations Atmospheric Sciences Oceanography Maritime Engineering Meteorology & Atmospheric Sciences Frants, Marina Damerell, Gillian M Gille, Sarah T Heywood, Karen J MacKinnon, Jennifer Sprintall, Janet An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
topic_facet |
Diapycnal mixing Mixing In situ oceanic observations Ship observations Atmospheric Sciences Oceanography Maritime Engineering Meteorology & Atmospheric Sciences |
description |
Finescale estimates of diapycnal diffusivity κ are computed from CTD and expendable CTD (XCTD) data sampled in Drake Passage and in the eastern Pacific sector of the Southern Ocean and are compared against microstructure measurements from the same times and locations. The microstructure data show vertical diffusivities that are one-third to one-fifth as large over the smooth abyssal plain in the southeastern Pacific as they are in Drake Passage, where diffusivities are thought to be enhanced by the flow of theAntarctic CircumpolarCurrent over rough topography. Finescalemethods based on vertical strain estimates are successful at capturing the spatial variability between the low-mixing regime in the southeastern Pacific and the high-mixing regime of Drake Passage. Thorpe-scale estimates for the same dataset fail to capture the differences between Drake Passage and eastern Pacific estimates. XCTD profiles have lower vertical resolution and higher noise levels after filtering than CTD profiles, resulting in XCTD κ estimates that are, on average, an order of magnitude higher than CTD estimates. Overall, microstructure diffusivity estimates are better matched by strain-based estimates than by estimates based on Thorpe scales, and CTD data appear to perform better than XCTD data. However, even the CTD-based strain diffusivity estimates can differ from microstructure diffusivities by nearly an order of magnitude, suggesting that density-based fine-structure methods of estimating mixing from CTD or XCTD data have real limitations in low-stratification regimes such as the Southern Ocean. © 2013 American Meteorological Society. |
format |
Article in Journal/Newspaper |
author |
Frants, Marina Damerell, Gillian M Gille, Sarah T Heywood, Karen J MacKinnon, Jennifer Sprintall, Janet |
author_facet |
Frants, Marina Damerell, Gillian M Gille, Sarah T Heywood, Karen J MacKinnon, Jennifer Sprintall, Janet |
author_sort |
Frants, Marina |
title |
An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
title_short |
An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
title_full |
An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
title_fullStr |
An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
title_full_unstemmed |
An Assessment of Density-Based Finescale Methods for Estimating Diapycnal Diffusivity in the Southern Ocean |
title_sort |
assessment of density-based finescale methods for estimating diapycnal diffusivity in the southern ocean |
publisher |
eScholarship, University of California |
publishDate |
2013 |
url |
https://escholarship.org/uc/item/3ns2x13q https://escholarship.org/content/qt3ns2x13q/qt3ns2x13q.pdf https://doi.org/10.1175/jtech-d-12-00241.1 |
op_coverage |
2647 - 2661 |
genre |
Drake Passage Southern Ocean |
genre_facet |
Drake Passage Southern Ocean |
op_source |
Journal of Atmospheric and Oceanic Technology, vol 30, iss 11 |
op_relation |
qt3ns2x13q https://escholarship.org/uc/item/3ns2x13q https://escholarship.org/content/qt3ns2x13q/qt3ns2x13q.pdf doi:10.1175/jtech-d-12-00241.1 |
op_rights |
public |
op_doi |
https://doi.org/10.1175/jtech-d-12-00241.1 |
container_title |
Journal of Atmospheric and Oceanic Technology |
container_volume |
30 |
container_issue |
11 |
container_start_page |
2647 |
op_container_end_page |
2661 |
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1810441385495494656 |