Hydrographic observations and mixing processes in the New York Bight, 1975-1977

Abstract

A series of 15 hydrographic cruises in the New York Bight over 1975-1977 is described and analyzed. The cruises cover all seasons but focus primarily on spring and summer. Temperature and salinity data show wide seasonal and interannual variability. Each of the three regions- inner bight, midshelf, and outer shelf slope-has distinctive properties and dynamics. The inner bight properties are affected primarily by river flow and wind-driven flows up the shelf valley which often splits the freshwater surface layer into two plumes, one east and one west of the valley head. The "cold pool" temperature structure on the midshelf is different each year. The water with the lowest recorded temperature (2.58°) was on the bottom after the thermocline formation in May 1977. Mixing models of the inner bight confirmed previous estimates of residence time as 6.8 days and yielded Kx = 5 x 10 6 cm2 g-1 with an advective transport component of 1 cm. s-1 to the southwest. A model of the mixing of the lower layer cold pool on the midshelf with onshore, offshore, and upper layer waters yields Kx = 7 x 106 and Kz = 0.1 cm 2. s-1 as the on-offshore horizontal and vertical diffusion coefficients. © 1981, by the American Society of Limnology and Oceanography, Inc.