Hydrographic conditions associated with the relaxation of an upwelling event off the Galician coast (NW Spain)

Abstract

During the GALICIA-XI cruise from May 10 to May 14, 1991, the relaxation of a previous strong tipwelling event took place along the Galician coast caused by a shift in the position of the Azores High. The coldest temperatures and highest nitrate levels were forrod near the coast corresponding to the advection of subsurface waters, particularly of Eastern North Atlantic Water (ENAW). On the basis of thermohaline properties, ENAW of polar (ENAWp) and tropical (ENAWt) origin are distinguished. The highest salinity values found correspond to a saline wedge of ENAWt located off the west coast of Galicia. The relaxation of tipwelling produced a shoreward migration of surface water from oceanic stations which crone into contact with upwelled Eastern North Atlantic Water from the coastal stations to form a convergence front 28 lan off the coast. Meanwhile, the saline wedge displaced towards both the north and the shore which is favored by the compression of the tipwelling system to a narrow coastal strip outwardly limited by the convergence zone