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Title: Observations and analysis of the Iceland Faeroes Front
Author: Allen, John Taylor
ISNI:       0000 0001 2423 6067
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1996
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Cyclonic and anticyclonic eddies at scales from 15 km to 70 km diameter were observed. Some of these eddies were virtually stationary. The meanders from which these eddies broke, however, were observed to move eastwards along the front in a manner typical of a region of baroclinic instability. Estimates of the phase speed and wavelength are presented and compared with theoretical models of frontal instability. As one of three regions where Atlantic water is mixed north into the Nordic Seas, the IFF plays an important role in global ocean circulation. Using simple analytical models of the observed eddies and an estimate of the generation rate of eddies at the IFF, the salt and heat fluxes across the IFF are calculated and compared with previous flux estimates. The IFF is a region where tidal flows are expected to be of the same magnitude as those of the frontal jet. The steeply sloping topography of the Iceland Fær�s Ridge causes large spatial variations in the amplitude and phase of the tide. Empirical tidal analyses carried out on a combination of ship mounted and moored ADCP data are presented. The success of the analysis techniques is assessed by making quantitative comparisons of the results, and with predictions from a numerical tidal model of the N. Atlantic. Additionally, stream functions calculated from the residual sub-tidal currents are examined and compared with hydrographic data. Synoptic maps of the vorticity and potential vorticity on isopycnal surfaces are presented. These are used to diagnose the dynamical processes occurring at the front. A cyclonic vortex was observed to spin up from an unstable meander propagating eastwards along the front. Within the vortex the magnitude of the relative vorticity was large (�0.8f), and the potential vorticity had high values similar to that of the water to the north of the front from which the vortex was derived. Vertical velocities are calculated using the quasi-geostrophic form of the omega equation. The eddy propagated north eastwards relative to the underlying water resulting in large upward (downward) vertical velocities (of the order of 100 m day⁻¹) ahead of (behind) the vortex.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Eddies; Tidal flows; Mesoscale instabilities