ANDREW C. THOMAS ...... the Northeast Channel, create distinct water masses (Hopkins and Garfield, ... Maine Bottom Water (Hopkins and Garfield, 1979).
Chapter 5 in: Robinson, A.R. and K.H. Brink (eds). 2004. The Sea: The Global Coastal Ocean: Interdisciplinary Regional Studies and Syntheses. Harvard University Press (in press).
OCEANOGRAPHY OF THE NORTHWEST ATLANTIC CONTINENTAL SHELF (1,W)
DAVID W. TOWNSEND ANDREW C. THOMAS LAWRENCE M. MAYER MAURA A. THOMAS School of Marine Sciences, University of Maine JOHN A. QUINLAN Institute of Marine and Coastal Sciences, Rutgers University Contents 1. Introduction 2. Large Scale Setting 2.1. Physiography 2.2. Circulation and Water Masses 2.3. Influence of North Atlantic Oscillation 2.4. Frontal Features 2.5. The Gulf Stream 2.6. Sedimentary Characteristics and Processes 3. Regional Shelf Systems 3.1. Nova Scotian Shelf 3.2. The Gulf of Maine 3.3. Georges Bank 3.4. Southern New England and Middle Atlantic Bight 4. Summary Acknowledgments Bibliography
1. Introduction This review (Region 1, W) covers coastal and shelf waters of the North Atlantic Ocean from Cabot Strait, situated between Nova Scotia and Newfoundland, to Cape Hatteras, North Carolina (from approximately 47°N to 35°N latitude; Fig. 5.1). It includes the shelf regions off the mouth of the Gulf of St. Lawrence, the Nova Scotian Shelf, Georges Bank and the Gulf of Maine, the southern New England Shelf, and the Middle Atlantic Bight. The continental shelves throughout the region are broad, especially off Nova Scotia and the Gulf of Maine, and extend more than 200 km offshore. They are cut by a number of deep channels, most notably the Laurentian Channel (>300 m) which runs through the Gulf of St. Lawrence, and the Northeast Channel (>250 m) at the mouth of the Gulf of Maine (Fig. 5.1); each provides an important connection between shelf waters and the open ocean. Several major rivers – especially the St. Lawrence River and the Hudson River – and many more smaller rivers and streams collectively contribute significant volumes of freshwater to the coasts. An 1
Chapter 5 in: Robinson, A.R. and K.H. Brink (eds). 2004. The Sea: The Global Coastal Ocean: Interdisciplinary Regional Studies and Syntheses. Harvard University Press (in press).
additional volume of freshwater, approximately equal to that from local rivers and streams, is delivered to the shelf regions as part of the coastal limb of the Labrador Current. Generally speaking, coastal and shelf waters throughout the region support extensive and productive fisheries. Their relatively high biological productivity results from a number of interacting features and processes, including cross-isobath fluxes of nutrient-rich deep waters, which occurs year round, and winter convective mixing. Winter mixing annually replenishes surface nutrient concentrations, setting the stage for important winter-spring plankton blooms that often commence in cold water temperatures (
