Water mass and acoustic analysis of the East Greenland Current

Abstract

Two cluster analysis techniques, one heuristic and one iterative, are employed to investigate the special coherence of the water masses of the East Greenland Current (EGC), in the vicinity of the East Greenland Polar Front (EGPF). Both techniques are shown to be generally reliable, although the iterative technique is more consistent with classical oceanographic analysis. The techniques are applied to data to explore the multiple and single variable data. The cluster technique is shown to have applications in planning a sonobuoy pattern and in assessing the validity of XBT data prior to an acoustic forecast. Acoustical analysis shows that acoustic reciprocity does not hold for propagation in the waters of the EGC. Ranges from shallow to deep water are far in excess of those from deep or shallow water. Propagation across the EGPF is significantly different for normal and oblique cases. Propagation loss fo oblique ranges is between 60 to 80% of perpendicular ranges, mostly due to different source sound speed profiles. Three acoustic models, FACT, RAYMODE and PE are compared and contrasted. PE is found to be the most consistent and reliable, although both FACT and RAYMODE compare satisfactorily for propagation from shallow to deep water. However, for the reverse case, FACT overestimates ranges by a factor of two, whereas RAYMODE is exceedingly over optimistic in its forecast ranges.