Sea surface temperature variability of the Iceland‐Faeroe front

Abstract

Several advanced very high resolution radiometer (AVHRR) images with spatial resolution of 1.1–3.3 km, together with several concurrent aircraft‐deployed expendable bathythermograph (AXBT) surveys and conductivity‐temperature‐depth (CTD) stations, from spring 1989 are used to describe the Iceland‐Faeroe sea surface temperature (SST) front. In the AVHRR images, SST fronts are located by maximizing |∇SST|. Single, large gradient segments of the SST front do exist, with some exceeding 100 km in length, indicating a multiple frontal structure. These single frontal lines are also segments where |∇2SST| is small, and they can be followed uniquely by a single isotherm eastward from Iceland for a distance of 300 km. With a 35‐km sampled AXBT survey, two small subsurface cold eddies were located south of the surface front in an area 170 km × 270 km east of Iceland. From a May 1987 AVHRR image on 1.1‐km resolution, a population of seven such cold eddies are found between Iceland and the Faroes. They appear to be generated along the surface expression of the Iceland Faroes front and populate the northern slope of the Iceland‐Faroes Ridge. Historical data from towed high‐resolution instruments suggest that the cold eddies are ∼30–50 km in size and uplift the main thermocline by 150 m.