A study of the Iceland-Faeroe Front using GEOSAT altimetry and current-following drifters

Abstract

In this study we investigate the utility of GEOSAT altimetry for monitoring the Iceland-Faeroe frontal zone. Since an expected dynamic topography relief of 10–20 cm over the Iceland-Faeroe Front (IFF) was not much above the 10 cm uncertainty in GEOSAT observations, validation by AVHRR imagery and satellite-tracked drifters constituted an important part of the experiment. Sea Surface Height (SSH) relief of greater than 20 cm occurred a long the western side of the IFF and along the eastern side, north of the Shetland Islands. However, with SSH relief of only 10–15 cm in the central region of the IFF, substantial difficulties were encountered in the ability to unambiguously monitor the location of the front. In contrast, frontal meanders with 20–30 cm SSH relief, current speeds up to 50 cm s⁻¹ and radii of curvature of 25 km, were clearly observed on three occasions during the 2 year study. These meanders first appeared north of the Faeroe Islands, in the region from 6 to 8°W, and propagated southeastward at speeds of about 3.3 km day⁻¹, being lost from view in the Faeroe-Shetland Channel. Their strong signals and lifetimes of 2–3 months would appear to make them important constituents of IFF dynamics.