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northwest Atlantic shelf Associated Investigators: Related Web Sites: Related Time Series: The flow of subpolar water toward the equator has a major influence on the entire northeastern North American seaboard. Relatively cool freshwater is transported from the north to the Labrador and Newfoundland shelves and then onward to the Gulf of St. Lawrence, Scotian Shelf, and the Gulf of Maine. The Scotian Shelf has two partially interconnected sources of subpolar water: (i) Cabot Strait outflow, which bifurcates to supply the Nova Scotian Current on the inner shelf and a shelf-break flow on the western side of Laurentian Channel and the outer Scotian Shelf; and (ii) the direct flow of Labrador Current water across the Laurentian Channel from the southern Newfoundland Shelf, primarily on the outer shelf. Thus, the flow is generally toward the equator on the Scotian Shelf, but with some cross-shelf meandering of the current branches and with a large reduction in net transport compared to the Labrador and Newfoundland shelves. The eastern end of the Scotian Shelf is dominated by the outflow from the Gulf of St. Lawrence with characteristic physical, chemical, and biological properties. The strength of this outflow (and, in fact, the inflow to the Gulf as well) is best measured at Cabot Strait, where the currents are confined to a small area. On the eastern portion of the shelf, the waters spread out more and some influence of offshore slope waters are felt, particularly over the outer banks. In the central shelf area, there is a very strong influence from slope water that has moved onshore and filled the inner basins. To the west, near the entrance to the Gulf of Maine-Bay of Fundy, tidal mixing is dominant and profoundly affects the vertical distribution of water properties. These different oceanographic regimes of the Scotian Shelf are sampled (1) at the eastern end of the shelf, where St. Lawrence water dominates but slope water is exerting a significant influence; (2) at the central shelf, where slope water plays a greater, if not dominant, role; and (3) at the western end of the shelf, where tidal mixing fundamentally alters water mass structure. A comprehensive environmental monitoring program, building on existing monitoring activities, was designed and implemented in 1999 for the northwestern Atlantic with the aim of increasing capacity to understand, describe, and forecast the state of the ocean environment and marine ecosystem. The main objectives of the Atlantic Zone Monitoring Program (AZMP) are twofold: (1) to collect and analyse biological, chemical, and physical data to characterise and understand the causes of oceanic variability at the seasonal, interannual: and decadal scales; and (2) to provide the multidisciplinary data sets that can be used to establish relationships among the biological, chemical, and physical variability. REFERENCES: Li, W.K.W. 2014. The state of phytoplankton and bacterioplankton on the Scotian Shelf and Slope: Atlantic Zone Monitoring Program 1997-2013. Can. Tech. Rep. Hydrogr. Ocean. Sci. 303: xx + 140 p. Themault, J.-C., B. Petrie, P. Pepin, J. Gagnon, D. Gregory, J. Helbig, A. Herrnan, D. Lefaivre, M. Mitchell, B. Pelchat, J. Runge, and D. Sarneoto. 1998. Proposal for a northwest Atlantic zonal monitoring program. Can. Tech. Rep. Hydrogr. Ocean Sci. 194: vii+57 p. |