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The buoyancy budget with a nonlinear equation of state
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2013 (English)In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 43, no 1, 176-186 p.Article in journal (Refereed) Published
Abstract [en]

The nonlinear equation of state of seawater introduces a sink or source of buoyancy when water parcels of unequal salinities and temperatures are mixed. This article contains quantitative estimates of these nonlinear effects on the buoyancy budget of the global ocean. It is shown that the interior buoyancy sink can be determined from surface buoyancy fluxes. These surface buoyancy fluxes are calculated using two surface heat flux climatologies, one based on in situ measurements and the other on a reanalysis, in both cases using a nonlinear equation of state. It is also found that the buoyancy budget in the ocean general circulation model Nucleus for European Modeling of the Ocean (NEMO) is in good agreement with the buoyancy budgets based on the heat flux climatologies. Moreover, an examination of the vertically resolved buoyancy budget in NEMO shows that in large parts of the ocean the nonlinear buoyancy sink gives the largest contribution to this budget.

Place, publisher, year, edition, pages
2013. Vol. 43, no 1, 176-186 p.
National Category
Oceanography, Hydrology, Water Resources
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-88327DOI: 10.1175/JPO-D-12-063.1ISI: 000314179300013OAI: oai:DiVA.org:su-88327DiVA: diva2:611794
Funder
Swedish Research Council, 2008-4400
Note

AuthorCount:2;

Available from: 2013-03-18 Created: 2013-03-12 Last updated: 2017-12-06Bibliographically approved
In thesis
1. An investigation into ocean thermodynamics and water-mass transformation
Open this publication in new window or tab >>An investigation into ocean thermodynamics and water-mass transformation
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents oceanic budgets of potential temperature, salinity and buoyancy as well as a novel way of diagnosing water-mass transformation in salinity-temperature space. The buoyancy of seawater is given by a nonlinear function of temperature, salinity and pressure and much of the work in this thesis revolves around how fluxes of heat and salinity influence the buoyancy of seawater through these nonlinearities.

Another large part of the material in this thesis is aimed at quantifying the relative importance of different processes for the vertical transport of heat and salinity in the ocean. Careful analysis of those fluxes in an ocean model reveal the different effects of e.g. advection, diffusion and penetrative shortwave radiation. An interesting finding is that the diffusive fluxes due to isoneutral diffusion (diffusion along density surfaces) and dianeutral diffusion (diffusion across density surfaces) have opposing effects on the oceanic heat and salinity budgets.

The final major topic of this thesis is water-mass transformation. A quantitative framework for the study of water-mass transformation in salinity-temperature space is introduced. A continuity equation is also derived for salinity-temperature space, which can be used to calculate the time rate of change of volume in a small salinity-temperature interval. The water-mass transformation framework is applied in an ocean general circulation model, and it is shown how the volume distribution in salinity-temperature space is affected by the different tracer fluxes in the model. It is also shown how the transformation framework is related to earlier work on thermohaline streamfunctions.

Place, publisher, year, edition, pages
Stockhom: Department of Meteorology, Stockholm University, 2014. 43 p.
Keyword
Ocean thermodynamics, water-mass transformation, buoyancy
National Category
Oceanography, Hydrology, Water Resources
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-103040 (URN)978-91-7447-919-5 (ISBN)
Public defence
2014-06-03, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2014-05-12 Created: 2014-04-29 Last updated: 2014-05-13Bibliographically approved

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