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Water Mass Transformation in Salinity–Temperature Space
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2014 (English)In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 44, no 9, p. 2547-2568Article in journal (Refereed) Published
Abstract [en]

This article presents a new framework for studying water mass transformations in salinity–temperature space that can, with equal ease, be applied to study water mass transformation in spaces defined by any two conservative tracers. It is shown how the flow across isothermal and isohaline surfaces in the ocean can be quantified from knowledge of the nonadvective fluxes of heat and salt. It is also shown how these cross-isothermal and cross-isohaline flows can be used to form a continuity equation in salinity–temperature space. These flows are then quantified in a state-of-the-art ocean model. Two major transformation cells are found: a tropical cell driven primarily by surface fluxes and dianeutral diffusion and a conveyor belt cell where isoneutral diffusion is also important. Both cells are similar to cells found in earlier work on the thermohaline streamfunction. A key benefit with this framework over a streamfunction approach is that transformation due to different diabatic processes can be studied individually. The distributions of volume and surface area in ST space are found to be useful for determining how transformations due to these different processes affect the water masses in the model. The surface area distribution shows that the water mass transformations due to surface fluxes tend to be directed away from ST regions that occupy large areas at the sea surface.

Place, publisher, year, edition, pages
2014. Vol. 44, no 9, p. 2547-2568
Keywords [en]
Circulation/ Dynamics, Atmosphere-ocean interaction, Meridional overturning circulation, Mixing, Ocean circulation, Streamfunction, Thermocline circulation
National Category
Oceanography, Hydrology and Water Resources
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-103214DOI: 10.1175/JPO-D-13-0257.1ISI: 000341334300016OAI: oai:DiVA.org:su-103214DiVA, id: diva2:716397
Available from: 2014-05-09 Created: 2014-05-09 Last updated: 2018-04-16Bibliographically 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. p. 43
Keywords
Ocean thermodynamics, water-mass transformation, buoyancy
National Category
Oceanography, Hydrology and 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: 2018-01-11Bibliographically approved

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