Potential vorticity in models of the ocean circulation

Bryan, Kirk

doi:10.1002/qj.49711347703

Cited by 15 publications

(5 citation statements)

References 31 publications

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“…One of the parameters we have chosen to present is potential vorticity. Its importance for understanding the general circulation of the ocean has been discussed by Rhines [1986] and Bryan [1987]. To the best of our knowledge, Neumann [1958] was the first investigator to apply potential vorticity as derived by Ertel [1942] to oceanographic data.…”

Section: Resultsmentioning

confidence: 99%

Interpentadal variability of temperature and salinity at intermediate depths of the north Atlantic Ocean, 1970–1974 versus 1955–1959

Levitus¹

1989

J. Geophys. Res.

151

100

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We have composited historical hydrographic observations for the world ocean for two pentads, 1955–1959 and 1970–1974, and have objectively analyzed these data for the purpose of studying the temporal variability of temperature and salinity in the North Atlantic Ocean. The subtropical gyre (500–1300 m) of the North Atlantic was colder and fresher during 1970–1974 compared to 1955–1959. The relatively large changes in temperature and salinity on constant‐depth surfaces in the subtropical gyre were due to upward displacements of isopycnal surfaces. At intermediate depths the eastern portion of the subarctic gyre was also colder and fresher during the 1970–1974 pentad. In contrast, the western portion of the subarctic gyre exhibited higher temperatures and salinities during 1970–1974 compared to 1955–1959. Characteristic differences in temperature and salinity for both gyres were 0.5°C and 0.025‰, respectively. Analysis of changes in potential vorticity indicates that in the subtropical gyre potential vorticity increased in all density layers above the 26.5 surface, suggesting that convection in this region may have been shallower in 1970–1974 compared to 1955–1959. Below the 26.5 surface, potential vorticity decreased through the 27.3 surface, indicating that deeper than normal convection may have formed the water masses in these layers. At 250‐m depth, relatively large changes in temperature and salinity occurred along the line of maximum climatological mixed layer depth that extends northeast to southwest across the North Atlantic Ocean.

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Section: Resultsmentioning

confidence: 99%

Interpentadal variability of temperature and salinity at intermediate depths of the north Atlantic Ocean, 1970–1974 versus 1955–1959

Levitus¹

1989

J. Geophys. Res.

151

100

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“…For passive tracers from the oceanic observations, the isopycnal eddy diffusivity and viscosity may is on the order of 10 3 m 2 /s [7], it varies from 10 2 m 2 /s [8] [9] [10] to more than 10 4 m 2 /s [11] [12] [13]. The results show that eddy mixing rates depend not on a simple relationship as suggested before.…”

mentioning

confidence: 55%

The Lateral Eddy Viscosity Derived from the Decay of Oceanic Mesoscale Eddies

Li¹,

Liang²,

Chi³

2018

OJMS

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The relationship of lateral eddy viscosity depending on length scale is estimated with the decay rate of mesoscale eddies identified from sea level anomaly of satellite observations. The eddy viscosity is expressed in terms of the mesoscale eddy parameters according to vortex dynamics. The census of mesoscale eddies shows, in general, that the eddy numbers obey the e-folding decay laws in terms of their amplitude, area and lifetime. The intrinsic values in the e-folding laws are used to estimate the lateral eddy viscosity. Dislike the previous theory that diffusivities are proportional to the length square, the eddy mixing rates (diffusivity and viscosity) from satellite mesoscale eddy datasets are proportional to r s to power of 1.8 (slightly less than 2), where r s is the radius of eddy with radius larger than the Batchelor scale. Additionally, the extrapolation of the eddy mixing to the molecule scale implies that the above power laws may hold until the value of r s is less than O (1 m). These mixing rates with the new parameterizations are suggested to use in numerical schemes. Finally, the climatological distributions of eddy viscosity are calculated.

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“…The GFDL coupled ocean-atmosphere model as described in (Manabe and Stouffer 1994) consists of an atmospheric model using the spectral element method with nine vertical levels. This atmospheric model is coupled to an ocean model with a 4.5°l atitude and 3.7°longitude resolution, 12 finite difference vertical levels, and isopycnal mixing following (Bryan 1987). The model assumes that ice sheets do not melt.…”

Section: A Scientific Analysismentioning

confidence: 99%

Early Detection of Changes in the North Atlantic Meridional Overturning Circulation: Implications for the Design of Ocean Observation Systems

et al. 2007

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Many climate models predict that anthropogenic greenhouse gas emissions may cause a threshold response of the North Atlantic meridional overturning circulation (MOC). These model predictions are, however, uncertain. Reducing this uncertainty can have an economic value, because it would allow for the design of more efficient risk management strategies. Early information about the MOC sensitivity to anthropogenic forcing (i.e., information that arrives before the system is committed to a threshold response) could be especially valuable. Here the focus is on one particular kind of information: the detection of anthropogenic MOC changes. It is shown that an MOC observation system based on infrequent (decadal scale) hydrographic observations may well fail in the task of early MOC change detection. This is because this system observes too infrequently and the observation errors are too large. More frequent observations and reduced observation errors would result in earlier detection. It is also shown that the economic value of information associated with a confident and early prediction of an MOC threshold response could exceed the costs of typically implemented ocean observation systems by orders of magnitude. One open challenge is to identify a feasible observation system that would enable such a confident and early MOC prediction across the range of possible MOC responses.

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Potential vorticity in models of the ocean circulation

Cited by 15 publications

References 31 publications

Interpentadal variability of temperature and salinity at intermediate depths of the north Atlantic Ocean, 1970–1974 versus 1955–1959

Interpentadal variability of temperature and salinity at intermediate depths of the north Atlantic Ocean, 1970–1974 versus 1955–1959

The Lateral Eddy Viscosity Derived from the Decay of Oceanic Mesoscale Eddies

Early Detection of Changes in the North Atlantic Meridional Overturning Circulation: Implications for the Design of Ocean Observation Systems

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