Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2016 The Southern Ocean is one of the most energetic regions of the world ocean due to intense winds and storm fo...
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/8079 2023-05-15T13:48:30+02:00 Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean Merrifield, Sophia T. Antarctic Ocean 2016-06 https://hdl.handle.net/1912/8079 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/8079 doi:10.1575/1912/8079 doi:10.1575/1912/8079 Oceanic mixing Mathematical models Thomas G. Thompson (Ship) Cruise US2 James Clark Ross (Ship) Cruise UK2 James Clark Ross (Ship) Cruise UK2.5 James Clark Ross (Ship) Cruise UK4 James Cook (Ship) Cruise UK3 Nathaniel B. Palmer (Ship) Cruise US5 Thesis 2016 ftwhoas https://doi.org/10.1575/1912/8079 2022-05-28T22:59:36Z Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2016 The Southern Ocean is one of the most energetic regions of the world ocean due to intense winds and storm forcing, strong currents in the form of the Antarctic Circumpolar Current (ACC) interacting with steep topography, and enhanced mesoscale activity. Consequently, the Southern Ocean is believed to be a hotspot for enhanced oceanic mixing. Due to the remote location and harsh conditions, few direct measurements of turbulence have been collected in the Southern Ocean. Previous studies have used indirect methods based on finestructure observations to suggest that strong mixing is ubiquitous below the mixed layer. Results from a US/UK field program, however, showed that enhanced internal wave finestructure and turbulence levels are not widespread, but limited to frontal zones where strong bottom currents collide with steep, large amplitude topography. This thesis studies the processes that support turbulence and mixing in the surface boundary layer and at intermediate depths in the Drake Passage region. Direct measurements of turbulence show that previous estimates of mixing rates in the upper 1km are biased high by up to two orders of magnitude. These biases are discussed in the context of the internal wave environment and enhanced thermohaline finestructure. The dissipation rate of thermal variance is enhanced in the upper 1000m, with the highest values found in northern Drake Passage where water mass variability is the most pronounced. Double diffusive processes and turbulence both contribute to buoyancy flux, elevating the effective mixing efficiency above the canonical value of 0.2 in the upper 1km. Despite the prevalence of energetic wind events, turbulence driven by downward propagating near-inertial wave shear is weak below the mixed layer. The results of this study inform large-scale modeling efforts through ... Thesis Antarc* Antarctic Antarctic Ocean Drake Passage Southern Ocean Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Antarctic Southern Ocean The Antarctic Drake Passage Antarctic Ocean Woods Hole, MA |
institution |
Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Oceanic mixing Mathematical models Thomas G. Thompson (Ship) Cruise US2 James Clark Ross (Ship) Cruise UK2 James Clark Ross (Ship) Cruise UK2.5 James Clark Ross (Ship) Cruise UK4 James Cook (Ship) Cruise UK3 Nathaniel B. Palmer (Ship) Cruise US5 |
spellingShingle |
Oceanic mixing Mathematical models Thomas G. Thompson (Ship) Cruise US2 James Clark Ross (Ship) Cruise UK2 James Clark Ross (Ship) Cruise UK2.5 James Clark Ross (Ship) Cruise UK4 James Cook (Ship) Cruise UK3 Nathaniel B. Palmer (Ship) Cruise US5 Merrifield, Sophia T. Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
topic_facet |
Oceanic mixing Mathematical models Thomas G. Thompson (Ship) Cruise US2 James Clark Ross (Ship) Cruise UK2 James Clark Ross (Ship) Cruise UK2.5 James Clark Ross (Ship) Cruise UK4 James Cook (Ship) Cruise UK3 Nathaniel B. Palmer (Ship) Cruise US5 |
description |
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2016 The Southern Ocean is one of the most energetic regions of the world ocean due to intense winds and storm forcing, strong currents in the form of the Antarctic Circumpolar Current (ACC) interacting with steep topography, and enhanced mesoscale activity. Consequently, the Southern Ocean is believed to be a hotspot for enhanced oceanic mixing. Due to the remote location and harsh conditions, few direct measurements of turbulence have been collected in the Southern Ocean. Previous studies have used indirect methods based on finestructure observations to suggest that strong mixing is ubiquitous below the mixed layer. Results from a US/UK field program, however, showed that enhanced internal wave finestructure and turbulence levels are not widespread, but limited to frontal zones where strong bottom currents collide with steep, large amplitude topography. This thesis studies the processes that support turbulence and mixing in the surface boundary layer and at intermediate depths in the Drake Passage region. Direct measurements of turbulence show that previous estimates of mixing rates in the upper 1km are biased high by up to two orders of magnitude. These biases are discussed in the context of the internal wave environment and enhanced thermohaline finestructure. The dissipation rate of thermal variance is enhanced in the upper 1000m, with the highest values found in northern Drake Passage where water mass variability is the most pronounced. Double diffusive processes and turbulence both contribute to buoyancy flux, elevating the effective mixing efficiency above the canonical value of 0.2 in the upper 1km. Despite the prevalence of energetic wind events, turbulence driven by downward propagating near-inertial wave shear is weak below the mixed layer. The results of this study inform large-scale modeling efforts through ... |
format |
Thesis |
author |
Merrifield, Sophia T. |
author_facet |
Merrifield, Sophia T. |
author_sort |
Merrifield, Sophia T. |
title |
Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
title_short |
Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
title_full |
Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
title_fullStr |
Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
title_full_unstemmed |
Mechanisms for enhanced turbulence in the Drake Passage region of the Southern Ocean |
title_sort |
mechanisms for enhanced turbulence in the drake passage region of the southern ocean |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
2016 |
url |
https://hdl.handle.net/1912/8079 |
op_coverage |
Antarctic Ocean |
geographic |
Antarctic Southern Ocean The Antarctic Drake Passage Antarctic Ocean |
geographic_facet |
Antarctic Southern Ocean The Antarctic Drake Passage Antarctic Ocean |
genre |
Antarc* Antarctic Antarctic Ocean Drake Passage Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Ocean Drake Passage Southern Ocean |
op_source |
doi:10.1575/1912/8079 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/8079 doi:10.1575/1912/8079 |
op_doi |
https://doi.org/10.1575/1912/8079 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766249336957566976 |