DEVELOPMENT, PERSISTENCE, AND VARIABILITY OF UPWELLING FILAMENTS OFF THE ATLANTIC COAST OF THE IBERIAN PENINSULA

The development, persistence, and variability of upwelling filaments o ff the Atlantic coast of the Iberian Peninsula are examined by means o f advanced very high resolution radiometer infrared imagery observed b etween 1982 and 1990. These observations indicate that the regime is b roadly similar to than observed in the California Current system and i s closely related to the large scale wind climatology of the subtropic al gyre. Upwelling generally starts in late May or early June and pers ists until late September or early October. In May or June, a narrow b and of cold water of quite uniform width is observed along much of the west coast of the Iberian Peninsula. This band has a ''fringed'' appe arance; that is consists of many narrow ''fingers'' or cool water exte nding 20-30 km offshore. The major filament structures generally do no t begin to form until late July or August. The filaments appear first as bulges in the upwelling front. These bulges grow offshore to form f ilaments that reach their maximum length (200-250 km) in September. Th e lengths of the filaments gradually decrease until the filaments beco me relatively rare in Late October Typically, five or six developed fi laments are observed off the Iberian Peninsula late in the upwelling s eason. Most of these are associated with major topographic features of the region, in particular the large capes which are common to the nor th and south of the Peninsula. It is therefore postulated that the dom inant dynamical processes related to filament formation off Iberia is topographic forcing. The exceptions are two major filaments commonly o bserved along the more regular coastline of northern Portugal. It is h ypothesized that these filaments are formed by flow instabilites resul ting in meandering of the southward flowing jet. These instabilities m ay possible be initiated by the large capes of northern Spain.