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Title: Rossby waves and mean currents in the Southern Ocean
Author: Ash, Ellis R.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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Dynamics in the Southern Ocean are dominated by the Antarctic Circumpolar Current (ACC), and this large eastward current has an important influence on the earth's climate. Output from the last six years of the Fine Resolution Antarctic Model, where the mean flow is known, is used to develop techniques for quantifying Rossby waves and eddy activity. Some eastward jets in the mean flow are found to act as waveguides for Rossby waves. Phase speeds are found to increase linearly with frequency, but do not vary with the strength of mean flow. The reason for this is demonstrated using the dispersion relation, but it is shown that Rossby waves cannot be used to measure mean flows in the ACC without a further understanding of the theory involved. A property of the time-average eddy activity, known as the eddy orientation angle, is shown to indicate the axes of the prominent eastward jets in the mean flow. This shows that eddies are acting to force these jets. Five yeas of measurements from the TOPEX/POSEIDON satellite mission are used to identify Rossby waves in the real ocean. Coherent Rossby wave propagation is again confined to localised regions, some of which act as waveguides. Phase speeds are measured in these regions, and shown to be consistent with previous measurements of Rossby waves. An improved resolution dataset, combining TOPEX/POSEIDON and ERS altimetry measurements, is used to analyse the time-average eddy activity and associated forcing on the mean flow in unprecedented detail. Current data from cruises of the World Ocean Circulation Experiment are used in conjunction with altimetry data to estimate the mean flow at locations along ship tracks. Using these estimates, and the position of temperature fronts as an indication of prominent jets in the mean flow, the eddy forcing is shown to be different to that observed in FRAM. Instead of forcing the mean flow, eddies are being generated within the jets which are likely to be maintained by topographic forcing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available