Xue et al 1

Penobscot Bay, with approximate dimensions 50 x 100 km, is the largest estuarine embayment along the Maine coast. It can be characterized by two deep channels on its eastern and western sides, which are separated by several islands and a shoal region in the middle of the Bay. Subtidal circulation in Penobscot Bay is influenced by winds, fresh water discharge from the Penobscot River, and the southwestward Maine Coastal Current flowing pass the mouth of the Bay. The Princeton Ocean Model was adapted to Penobscot Bay to simulate the circulation for the spring and summer of 1998. Observed winds at nearby Matinicus Rock and realistic river discharge rates were used to force the model. Open boundary conditions were specified using the results from a Gulf of Maine climatological model. Simulations were somewhat sensitive to the mixing coefficient in the model. When a background viscosity of 5x10-6 m2/s was used, the model reproduced the observed three-layer structure in the outer western bay with outflows near the surface and the bottom and inflows in the middle of the water column. In contrast, a two-layer estuarine like circulation was found in the outer eastern bay with outflows in the upper water column and inflows in the lower water column. 1