Tomographic measurements of frontal variability in the Barents Sea

Abstract

In August 1992 a coastal ocean tomography experiment was conducted in the Barents Sea over the steep northwestern slope of the Bear Island Trough, about 100 km east of Bear Island. The objective of the experiment was to map and study the oscillations of the Barents Sea Polar Front using acoustic tomography coupled with traditional hydrographic techniques. Because mesoscale ocean variability has shorter spatial and temporal scales in a coastal environment, a vertical receiving array and frequently transmitting tomography sound sources were used to achieve an enhanced system resolution appropriate for coastal monitoring. The vertical array data were processed using plane‐wave beamforming to separate ray arrivals in both time and angle. In addition, modal arrivals were separated using broadband modal beamforming techniques. The processed travel time data were then ‘‘inverted’’ using a hybrid ray‐mode inverse technique to produce a time series of maps of the polar front. In this presentation, the hybrid ray‐mode inverse method and the frontal variability as imaged by this shallow‐water tomography system are discussed. [Work supported by ONR 1125AR.]