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An Investigation of Cold Overflow Over the Iceland/Faeroes Ridge

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Master's thesis,

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Hydrographic data were analyzed to determine spatial and temporal variability of the overflow of cold, fresh Arctic water over the IcelandFaeroes Ridge into the Iceland Basin during both winter and summer. Regions of frequent intermittent overflow were located together with areas that remain relatively unaffected by this process. A time series of near bottom temperatures revealed a possible link between significant overflow events and local wind fields which may result in a seasonal contrast in conditions. Two overflow mechanisms were identified an intermittent plume-like flow promoted by local wind forcing and a continuous thin veil of mixed overflow water formed from more significantly sized eddiesfilaments located on top of the ridge. Estimates were made as to the probable contribution of both mechanisms to the total transport of Norwegian Sea water into the North Atlantic Ocean. Dynamic models of overflow were reviewed and, based on hydrographic results, a probable mechanism for overflow was proposed. Sound speed profiles were constructed representing the presence absence of overflow events and predicted sonar ranges were computed using a range-dependent parabolic equation model. Major effects on acoustic propagation are shown to be confined to regions close to the top of the rise, even during overflow events however, large reduction in sonar ranges are predicted for areas on top of the ridge, even at low frequencies 100 Hz. Analysis of observations in the area suggest that acoustic variability in the region can be related to small changes in sea surface temperature and consequently may lead to a prediction of acoustic conditions in the region using AVHRR imagery.

Subject Categories:

  • Meteorology
  • Physical and Dynamic Oceanography
  • Acoustics

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