Classic hydrography and air-sea interaction methodologies applied to coastal oceanography: The Northeast Water Polynya (northeast Greenland) and the North Carolina continental shelf.

摘要

Two areas of the World's coastal oceans have been studied from the physical point of view by means of classic hydrographic methods, remote sensing and atmospheric data. The analysis concerns the seasonal evolution and geographic distribution of water masses in the very different climatic settings of the Northeast Water Polynya, on the Greenland shelf southwest of Fram Strait, and the North Carolina shelf. Two cruises were carried out in the summers of 1992 and 1993 in the former area, while eight cruises covered the latter between February and October 1996.; The presence of a polynya, i.e. a region of open water of variable size in the otherwise ice-covered ocean off northeast Greenland allows for a vigorous sensible and latent heat exchange across the free surface during the winter months. A cold water mass is thereby formed, the Polynya Intermediate Water (PyIW), which plays the main role in the circulation pattern throughout the year. Estimates of its typical hydrographic values, its volume and of the thermodynamic parameters characterizing its formation and evolution during the summer months are given below.; The North Carolina shelf hydrography reveals the well known Cold Pool water, a shelf water type advected in spring into the area from the north, which is then overlaid by the summer warmer waters. This water mass is seen to gradually move offshore during the warm season, to give way to a fresher, warmer water type, mainly originating from runoff and/or precipitation. The exposure of the Cold Pool waters to the shelf break dynamics probably favors their dispersal and exhausts the yearly supply of this water by late Fall. The comparison between free surface and advective forcings in the seasonal evolution of these waters reveals the predominance of the action of ocean currents over atmospheric events, both for the summer and winter phases. In particular, shelf/slope exchange is necessary to explain the observed winter salting of the shelf waters and to prevent these to be excessively cooled by the atmosphere during the cold season.