THE SUMMER GYRE IN THE WESTERN IRISH SEA - SHELF SEA PARADIGMS AND MANAGEMENT IMPLICATIONS

A cyclonic, near-surface gyre has been discovered above the deep weste rn Irish Sea basin. The gyre, present in spring and summer each year, is formed when stratification isolates a dome of cold bottom water whi ch then drives a baroclinic circulation. Simultaneous observations usi ng ship-mounted, broad-band acoustic Doppler current profiler, towed u ndulating CTD (conductivity, temperature, depth) and satellite-tracked drifting buoys reveal the detailed horizontal and vertical structure of the gyre. Gyre dynamics have been investigated using a three-dimens ional, steady, diagnostic circulation model with realistic bathymetry. The role of the gyre within the existing Bowden-Simpson paradigm of s helf circulation is discussed. Knowledge of seasonal gyre systems is i mportant when formulating management strategies. For example, there is evidence that the Irish Sea gyre acts as a retention system for the p lanktonic larvae of the commercially valuable Norway lobster (Nephrops norvegicus, Linnaeus 1758) which inhabits the geographically isolated mud patch beneath the gyre. Moreover, in the event of an accidental s ummer-time spill, the gyre could also act to retain contaminants, sugg esting that this system is at disproportionate risk from environmental damage. (C) 1997 Academic Press Limited.