Aspects of the circulation in the Rockall Trough

An investigation is made of the circulation and structure of the water mass es in the Rockall Trough in spring, combining the results of a recent synop tic survey (May 1998) with those from a high-resolution ocean circulation m odel. In the near-surface layer, saline flows are carried northwards by a " Shelf Edge Current" around the eastern slopes, possibly with some branching in the northern Trough. Fresher waters from the west inflow between 52 and 53 degreesN and partially mix with these saline flows in the southern Trou gh, so that waters of intermediate salinity are also swept northwards. In t he southern approaches to the Trough, Labrador Sea Water (LSW) also flows s trongly in from the west between 52 and 53 degreesN, and while much of this turns south, a proportion penetrates north to join a cyclonic gyre in the Trough extending to 56.5 degreesN. The northwestern limb of this gyre is fe d by, and mixes with, more saline waters which result from overflows across the Wyville-Thomson Ridge. Furthermore, salinity and CFC data suggest epis odic inflow of LSW into the central Trough. The circulation of the North Ea st Atlantic Deep Water in the Trough follows a cyclonic pattern similar to, and lying below, that of the LSW. The Wyville-Thomson Ridge overflows in t he model extend to higher densities than in the survey, are topographically steered southwestward down the Feni Ridge system, and eventually join a de ep cyclonic circulation in the North East Atlantic basin. Overall, the mode l and the observations are in good agreement, particularly in the central R ockall Trough, and this has allowed conclusions to be drawn which are signi ficantly more robust than those which would result from either the survey o r the model alone. In particular, we have been able to infer cyclonic circu lation pathways for the intermediate and deeper waters in the Rockall Troug h for (we believe) the first time. The study has also contributed to an ong oing community effort to assess the realism of, and improve, our current ge neration of ocean circulation models. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.