Subduction in an eddy-resolving state estimate of the northeast Atlantic 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 2004 Relatively little is known about the role of eddies in controlling subduction in the eastern half of the sub...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/2068 2023-05-15T17:30:42+02:00 Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean Gebbie, Geoffrey A. Eastern North Atlantic Ocean 2004-06 application/pdf https://hdl.handle.net/1912/2068 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/2068 doi:10.1575/1912/2068 doi:10.1575/1912/2068 Subduction zones Seismic prospecting Marine sediments Beryllium Isotopes Radioisotopes in oceanography Thesis 2004 ftwhoas https://doi.org/10.1575/1912/2068 2022-05-28T22:57:28Z 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 2004 Relatively little is known about the role of eddies in controlling subduction in the eastern half of the subtropical gyre. Here, a new tool to study the eastern North Atlantic Ocean is created by combining a regional, eddy-resolving numerical model with observations to produce a state estimate of the ocean circulation. The estimate is a synthesis of a variety of in-situ observations from the Subduction Experiment, TOPEX/POSEIDON altimetry, and the MIT General Circulation Model. A novel aspect of this work is the search for an initial eddy field and eddy-scale open boundary conditions by the use of an adjoint model. The adjoint model for this region of the ocean is stable and yields useful information despite concerns about the chaotic nature of eddy-resolving models. The method is successful because the dynamics are only weakly nonlinear in the eastern region of the subtropical gyre. Therefore, no fundamental obstacle exists to constraining the model to both the large scale circulation and the eddy scale in this region of the ocean. Individual eddy trajectories can also be determined. The state estimate is consistent with observations, self-consistent with the equations of motion, and it explicitly resolves eddy-scale motions with a 1/6º grid. Therefore, subduction rates, volume budgets, and buoyancy budgets are readily diagnosed in a physically interpretable context. Estimates of eddy subduction for the eastern subtropical gyre of the North Atlantic are larger than previously calculated from parameterizations in coarse-resolution models. Eddies contribute up to 40 m/yr of subduction locally. Furthermore, eddy subduction rates have typical magnitudes of 15% of the total subduction rate. To evaluate the net effect of eddies on an individual density class, volume budgets are diagnosed. Eddies contribute as much as 1 Sv to ... Thesis North Atlantic Northeast Atlantic Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Woods Hole, MA |
institution |
Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Subduction zones Seismic prospecting Marine sediments Beryllium Isotopes Radioisotopes in oceanography |
spellingShingle |
Subduction zones Seismic prospecting Marine sediments Beryllium Isotopes Radioisotopes in oceanography Gebbie, Geoffrey A. Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
topic_facet |
Subduction zones Seismic prospecting Marine sediments Beryllium Isotopes Radioisotopes in oceanography |
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 2004 Relatively little is known about the role of eddies in controlling subduction in the eastern half of the subtropical gyre. Here, a new tool to study the eastern North Atlantic Ocean is created by combining a regional, eddy-resolving numerical model with observations to produce a state estimate of the ocean circulation. The estimate is a synthesis of a variety of in-situ observations from the Subduction Experiment, TOPEX/POSEIDON altimetry, and the MIT General Circulation Model. A novel aspect of this work is the search for an initial eddy field and eddy-scale open boundary conditions by the use of an adjoint model. The adjoint model for this region of the ocean is stable and yields useful information despite concerns about the chaotic nature of eddy-resolving models. The method is successful because the dynamics are only weakly nonlinear in the eastern region of the subtropical gyre. Therefore, no fundamental obstacle exists to constraining the model to both the large scale circulation and the eddy scale in this region of the ocean. Individual eddy trajectories can also be determined. The state estimate is consistent with observations, self-consistent with the equations of motion, and it explicitly resolves eddy-scale motions with a 1/6º grid. Therefore, subduction rates, volume budgets, and buoyancy budgets are readily diagnosed in a physically interpretable context. Estimates of eddy subduction for the eastern subtropical gyre of the North Atlantic are larger than previously calculated from parameterizations in coarse-resolution models. Eddies contribute up to 40 m/yr of subduction locally. Furthermore, eddy subduction rates have typical magnitudes of 15% of the total subduction rate. To evaluate the net effect of eddies on an individual density class, volume budgets are diagnosed. Eddies contribute as much as 1 Sv to ... |
format |
Thesis |
author |
Gebbie, Geoffrey A. |
author_facet |
Gebbie, Geoffrey A. |
author_sort |
Gebbie, Geoffrey A. |
title |
Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
title_short |
Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
title_full |
Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
title_fullStr |
Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
title_full_unstemmed |
Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean |
title_sort |
subduction in an eddy-resolving state estimate of the northeast atlantic ocean |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
2004 |
url |
https://hdl.handle.net/1912/2068 |
op_coverage |
Eastern North Atlantic Ocean |
genre |
North Atlantic Northeast Atlantic |
genre_facet |
North Atlantic Northeast Atlantic |
op_source |
doi:10.1575/1912/2068 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/2068 doi:10.1575/1912/2068 |
op_doi |
https://doi.org/10.1575/1912/2068 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766127595287478272 |