THE WATER MASS CHARACTERISTICS OF THE NORTHEAST WATER POLYNYA - POLARSEA DATA 1992-1993

Hydrographic cruises in the summers of 1992 and 1993 were carried out in the North-Fast Water (NEW) Polynya. For both years, CTD casts on th e NEW Polynya shelf area yielded a signature of a highly homogeneous, cold (theta = -1.74 degrees C) and relatively fresh (S = 32.40 ppt) wa ter just below the surface pycnocline, which we refer to as the Northe ast Water Polynya Intermediate Water (PyIW). Its homogeneity, its loca tion and the fact that its core temperature is very close to the freez ing point all suggest that this water is formed convectively through a loss of buoyancy to the atmosphere over the open portions of the Poly nya, The source waters are the low salinity surface waters found in th e northern sector of the Polynya area. The thickness of the PyIW varie d from 10 to 60 m throughout the northern (Norske-Westwind trough syst em) and central (Belgica Bank) portion of shelf region. It was not fou nd over the slope nor in Belgica Trough immediately to the south, A vo lumetric theta-S analysis of the PyIW demonstrated that it suffered a small loss between the two years and that its areal distribution and c ore water type remained virtually constant, Some qualitative assessmen ts are made concerning its formation and loss. The small interannual v ariability of the PyIW layer implies a high residence time that has im portant physical and biological repercussions, The summer modification of the Polynya surface waters is also discussed; and by relating the water-type change with the summer heat budget, estimates of 47 and 75 cm were made for the amount of ice thinning occurring over the area fo r the two years, respectively. The water found below the sills (at sim ilar to 265 m) of the Norske-Westwind Trough system has a warmer (thet a = 0.78 degrees C) and saltier (S = 34.83 ppt) water type, than that of the PyIW, which characterizes it as a species of return Atlantic In termediate Water.