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The representation of ocean circulation and variability in thermodynamic coordinates
journal contribution
posted on 2023-05-18, 04:42 authored by Groeskamp, S, Zika, JD, McDougall, TJ, Sloyan, BM, Laliberte, FThe ocean’s circulation is analyzed in Absolute Salinity SA and Conservative Temperature Θ coordinates. It is separated into 1) an advective component related to geographical displacements in the direction normal to SA and Θ isosurfaces and 2) into a local component, related to local changes in SA–Θ values, without a geographical displacement. In this decomposition, the sum of the advective and local components of the circulation is equivalent to the material derivative of SA and Θ. The sum is directly related to sources and sinks of salt and heat. The advective component is represented by the advective thermohaline streamfunction Ψadv SAΘ. After removing a trend, the local component can be represented by the local thermohaline streamfunction Ψloc SAΘ. Here, Ψloc SAΘ can be diagnosed using a monthly averaged time series of SA and Θ from an observational dataset. In addition, Ψadv SAΘ and Ψloc SAΘ are determined from a coupled climate model. The diathermohaline streamfunction Ψdia SAΘ is the sum of Ψadv SAΘ and Ψloc SAΘ and represents the nondivergent diathermohaline circulation in SA–Θ coordinates. The diathermohaline trend, resulting from the trend in the local changes of SA and Θ, quantifies the redistribution of the ocean’s volume in SA–Θ coordinates over time. It is argued that the diathermohaline streamfunction provides a powerful tool for the analysis of and comparison among ocean models and observation-based gridded climatologies.
History
Publication title
Journal of Physical OceanographyVolume
44Issue
7Pagination
1735-1750ISSN
0022-3670Department/School
Institute for Marine and Antarctic StudiesPublisher
Amer Meteorological SocPlace of publication
45 Beacon St, Boston, USA, Ma, 02108-3693Rights statement
Copyright 2014 American Meteorological SocietyRepository Status
- Restricted