Compressibility effects in the Miami isopycnic coordinate ocean model
Potential density referenced to sea level pressure $(\sigma\sb0$) has shown its usefulness as vertical coordinate in ocean models in many ways, but there are problems with $\sigma\sb0$ (potential density referenced to sea level) coordinates in the deep ocean: $\sigma\sb0(z)$ can be multivalued, lead...
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ftunivmiamiir:oai:scholarlyrepository.miami.edu:dissertations-4461 2023-05-15T13:36:29+02:00 Compressibility effects in the Miami isopycnic coordinate ocean model Sun, Shan Rainer Bleck - Committee Chair 1997-01-01T08:00:00Z https://scholarlyrepository.miami.edu/dissertations/3462 unknown Scholarly Repository Dissertations from ProQuest Geophysics; Physical Oceanography; Engineering Marine and Ocean article 1997 ftunivmiamiir 2019-08-09T22:54:59Z Potential density referenced to sea level pressure $(\sigma\sb0$) has shown its usefulness as vertical coordinate in ocean models in many ways, but there are problems with $\sigma\sb0$ (potential density referenced to sea level) coordinates in the deep ocean: $\sigma\sb0(z)$ can be multivalued, leading to coordinate folding, and $\sigma\sb0$ surfaces can deviate from the so-called neutral surfaces, which are the surfaces along which turbulent lateral mixing takes place in a stratified medium. The reason for both of these problems is that most isopycnal models regard seawater as uniformly compressible. However, the effect of water temperature on compressibility cannot be ignored.In this study a two-pronged approach is taken to improve the model accuracy. First, since the effects of compressibility variation are proportional to the difference between the local and the reference pressure, we replace the model's traditional $\sigma\sb0$ coordinate by $\sigma\sb2$ (potential density referenced to 2000 dbar). This step eliminates many of the coordinate folding problems associated with $\sigma\sb0$ and generally reduces the difference between coordinate and neutrally buoyant surfaces. Second, we split the compressibility coefficient into a pressure- and a temperature-dependent part and, recognizing that the former is dynamically passive, retain only the effect of the latter in the governing equations. This is accomplished by introducing a new variable called "active density"--the density with the pressure-related compressibility removed. Therefore, $\sigma\sb2$ is adopted as vertical coordinate, but active density is used to express the seawater density within the layers.The above changes are applied in a near-global, 16-layer, 2$\sp\circ$ x 2$\sp\circ$cos (lat.) Miami Isopycnic Coordinate Ocean Model (MICOM). The model is driven by observed atmospheric conditions. MICOM modified in this fashion produces realistic meridional mass and associated heat fluxes in the three major ocean basins. A realistic formation rate of a few major water masses, including the North Atlantic Deep Water and the Antarctic Bottom Water, is also obtained. To summarize the various circulation features obtained by the model, a three-dimensional mass transport diagram spanning four density classes is constructed. Many features in it compare well with those revealed by observed hydrographic data. Article in Journal/Newspaper Antarc* Antarctic North Atlantic Deep Water North Atlantic University of Miami: Scholarly Repository Antarctic The Antarctic |
institution |
Open Polar |
collection |
University of Miami: Scholarly Repository |
op_collection_id |
ftunivmiamiir |
language |
unknown |
topic |
Geophysics; Physical Oceanography; Engineering Marine and Ocean |
spellingShingle |
Geophysics; Physical Oceanography; Engineering Marine and Ocean Sun, Shan Compressibility effects in the Miami isopycnic coordinate ocean model |
topic_facet |
Geophysics; Physical Oceanography; Engineering Marine and Ocean |
description |
Potential density referenced to sea level pressure $(\sigma\sb0$) has shown its usefulness as vertical coordinate in ocean models in many ways, but there are problems with $\sigma\sb0$ (potential density referenced to sea level) coordinates in the deep ocean: $\sigma\sb0(z)$ can be multivalued, leading to coordinate folding, and $\sigma\sb0$ surfaces can deviate from the so-called neutral surfaces, which are the surfaces along which turbulent lateral mixing takes place in a stratified medium. The reason for both of these problems is that most isopycnal models regard seawater as uniformly compressible. However, the effect of water temperature on compressibility cannot be ignored.In this study a two-pronged approach is taken to improve the model accuracy. First, since the effects of compressibility variation are proportional to the difference between the local and the reference pressure, we replace the model's traditional $\sigma\sb0$ coordinate by $\sigma\sb2$ (potential density referenced to 2000 dbar). This step eliminates many of the coordinate folding problems associated with $\sigma\sb0$ and generally reduces the difference between coordinate and neutrally buoyant surfaces. Second, we split the compressibility coefficient into a pressure- and a temperature-dependent part and, recognizing that the former is dynamically passive, retain only the effect of the latter in the governing equations. This is accomplished by introducing a new variable called "active density"--the density with the pressure-related compressibility removed. Therefore, $\sigma\sb2$ is adopted as vertical coordinate, but active density is used to express the seawater density within the layers.The above changes are applied in a near-global, 16-layer, 2$\sp\circ$ x 2$\sp\circ$cos (lat.) Miami Isopycnic Coordinate Ocean Model (MICOM). The model is driven by observed atmospheric conditions. MICOM modified in this fashion produces realistic meridional mass and associated heat fluxes in the three major ocean basins. A realistic formation rate of a few major water masses, including the North Atlantic Deep Water and the Antarctic Bottom Water, is also obtained. To summarize the various circulation features obtained by the model, a three-dimensional mass transport diagram spanning four density classes is constructed. Many features in it compare well with those revealed by observed hydrographic data. |
author2 |
Rainer Bleck - Committee Chair |
format |
Article in Journal/Newspaper |
author |
Sun, Shan |
author_facet |
Sun, Shan |
author_sort |
Sun, Shan |
title |
Compressibility effects in the Miami isopycnic coordinate ocean model |
title_short |
Compressibility effects in the Miami isopycnic coordinate ocean model |
title_full |
Compressibility effects in the Miami isopycnic coordinate ocean model |
title_fullStr |
Compressibility effects in the Miami isopycnic coordinate ocean model |
title_full_unstemmed |
Compressibility effects in the Miami isopycnic coordinate ocean model |
title_sort |
compressibility effects in the miami isopycnic coordinate ocean model |
publisher |
Scholarly Repository |
publishDate |
1997 |
url |
https://scholarlyrepository.miami.edu/dissertations/3462 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic North Atlantic Deep Water North Atlantic |
genre_facet |
Antarc* Antarctic North Atlantic Deep Water North Atlantic |
op_source |
Dissertations from ProQuest |
_version_ |
1766079164035629056 |