On the formation of shelf-break fronts

MATANO, R. P.; PALMA. E. D.

Honolulu, Hawaii

Congreso; Ocean Sciences 2006; 2006

American Geophysical Union

Early studies on the formation of shelfbreak fronts focused on the geostrophic adjustment to a prescribed density field (e.g., Hsueh and Cushman-Roisin, 1983; Ou, 1983 and 1984; Wang, 1984; Wright, 1989). In the early nineties Gawarkiewicz and Chapman (1992) presented a highly influential study that postulated that shelfbreak fronts are generated by alongshelf currents flowing in the direction of the coastally trapped waves. According to their arguments such currents generate an offshore flux of mass in the bottom boundary layer that leads to the formation of a density front at the shelfbreak. In this presentation we will describe the results of a series of numerical simulations focused on the formation of shelfbreak fronts. In the first part we analyze the sensitivity of the results of Gawarkiewicz and Chapman to the parameterization of vertical mixing. To that end we reproduced their model setup and replicated some of their benchmark experiments. Our re-analysis indicates that the mechanisms proposed by them are very sensitive to the parameterization of vertical mixing. We will also show numerical experiments designed to investigate the interaction between the shelf and the deep ocean circulation. These experiments indicate that the alongshelf gradient generated by the cross-shelf spreading of the slope current leads to the development of a relatively robust shelfbreak front. Additional experiments are used to discuss the sensitivity of these results to vertical mixing parameterization, strength of the shelf and slope inflows, and the magnitude of the vertical stratification.