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Title: A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity

Abstract

MPAS-Ocean is used to simulate an idealized, density-driven overflow using the dynamics of overflow mixing and entrainment (DOME) setup. Additionally, numerical simulations are carried out using three of the vertical coordinate types available in MPAS-Ocean, including z-star with partial bottom cells, z-star with full cells, and sigma coordinates. The results are first benchmarked against other models, including the MITgcm’s z-coordinate model and HIM’s isopycnal coordinate model, which are used to set the base case used for this work. A full parameter study is presented that looks at how sensitive overflow simulations are to vertical grid type, resolution, and viscosity. Horizontal resolutions with 50 km grid cells are under-resolved and produce poor results, regardless of other parameter settings. Vertical grids ranging in thickness from 15 m to 120 m were tested. A horizontal resolution of 10 km and a vertical resolution of 60 m are sufficient to resolve the mesoscale dynamics of the DOME configuration, which mimics real-world overflow parameters. Mixing and final buoyancy are least sensitive to horizontal viscosity, but strongly sensitive to vertical viscosity. This suggests that vertical viscosity could be adjusted in overflow water formation regions to influence mixing and product water characteristics. In conclusion, the study showsmore » that sigma coordinates produce much less mixing than z-type coordinates, resulting in heavier plumes that go further down slope. Sigma coordinates are less sensitive to changes in resolution but as sensitive to vertical viscosity compared to z-coordinates.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]
  1. Fairfield University School of Engineering, CT (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Brown Univ., Providence, RI (United States)
Publication Date:
Research Org.:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1492640
Alternate Identifier(s):
OSTI ID: 1263702
Report Number(s):
LA-UR-15-23609
Journal ID: ISSN 1463-5003
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Ocean Modelling
Additional Journal Information:
Journal Volume: 96; Journal Issue: P2; Journal ID: ISSN 1463-5003
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Dynamics of overflow mixing and entrainment (DOME); MPAS-Ocean; Sigma vertical coordinate; Z-star with partial bottom cells; Model resolution

Citation Formats

Reckinger, Shanon Marie, Petersen, Mark Roger, and Reckinger, Scott James. A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity. United States: N. p., 2015. Web. doi:10.1016/j.ocemod.2015.09.006.
Reckinger, Shanon Marie, Petersen, Mark Roger, & Reckinger, Scott James. A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity. United States. https://doi.org/10.1016/j.ocemod.2015.09.006
Reckinger, Shanon Marie, Petersen, Mark Roger, and Reckinger, Scott James. 2015. "A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity". United States. https://doi.org/10.1016/j.ocemod.2015.09.006. https://www.osti.gov/servlets/purl/1492640.
@article{osti_1492640,
title = {A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity},
author = {Reckinger, Shanon Marie and Petersen, Mark Roger and Reckinger, Scott James},
abstractNote = {MPAS-Ocean is used to simulate an idealized, density-driven overflow using the dynamics of overflow mixing and entrainment (DOME) setup. Additionally, numerical simulations are carried out using three of the vertical coordinate types available in MPAS-Ocean, including z-star with partial bottom cells, z-star with full cells, and sigma coordinates. The results are first benchmarked against other models, including the MITgcm’s z-coordinate model and HIM’s isopycnal coordinate model, which are used to set the base case used for this work. A full parameter study is presented that looks at how sensitive overflow simulations are to vertical grid type, resolution, and viscosity. Horizontal resolutions with 50 km grid cells are under-resolved and produce poor results, regardless of other parameter settings. Vertical grids ranging in thickness from 15 m to 120 m were tested. A horizontal resolution of 10 km and a vertical resolution of 60 m are sufficient to resolve the mesoscale dynamics of the DOME configuration, which mimics real-world overflow parameters. Mixing and final buoyancy are least sensitive to horizontal viscosity, but strongly sensitive to vertical viscosity. This suggests that vertical viscosity could be adjusted in overflow water formation regions to influence mixing and product water characteristics. In conclusion, the study shows that sigma coordinates produce much less mixing than z-type coordinates, resulting in heavier plumes that go further down slope. Sigma coordinates are less sensitive to changes in resolution but as sensitive to vertical viscosity compared to z-coordinates.},
doi = {10.1016/j.ocemod.2015.09.006},
url = {https://www.osti.gov/biblio/1492640}, journal = {Ocean Modelling},
issn = {1463-5003},
number = P2,
volume = 96,
place = {United States},
year = {Fri Oct 09 00:00:00 EDT 2015},
month = {Fri Oct 09 00:00:00 EDT 2015}
}

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Cited by: 19 works
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Works referenced in this record:

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Works referencing / citing this record:

The role of eddies on pathways, transports, and entrainment in dense water flows along a slope
journal, June 2019


Effects of the bottom boundary condition in numerical investigations of dense water cascading on a slope
journal, February 2018