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Chapter 4 - Physical OceanographyFigure 4-2. Mean tidal range in the Northwest Atlantic region (reprinted withpermission from Townsend et al. 2006).Figure 4-2 (from Townsend et al. 2006) shows thestrength of tides within the Northwest Atlantic region.The height of the black bar indicates the strength of thetide at that point. The strongest tides are in the Gulf ofMaine, particularly on the northern (Canadian) end bythe Bay of Fundy. Penobscot Bay and Cape Cod Bay alsohave a strong tidal influence, as does the western end ofLong Island Sound.OceanographicAnalysis: AnOverview ofMethodsFor all of the temperature-relatedanalyses described below, sourcedata was obtained from Dr. GrantLaw, Center for Coastal MarginObservation and Prediction, OregonHealth and Science University. Thedataset included temperature valuesplotted on a standard grid of threedimensionalpoint locations that hasfiner detail toward the shore andsurface, where there is greater needfor higher resolution. The data comprisedseasonal climatologies (Jan-Mar, Apr-Jun, Jul-Sep, Oct-Nov) toa depth of 2,500 m, from 1980-2007.Hydrographic observations were compiledfrom several sources, includingHydrobase, National Marine FisheriesService (NMFS), and Department ofFisheries and Oceans Canada (DFO).An archive of South Atlantic Bighthydrographic data assembled by BrianBlanton at UNC was also includedin the archive. All hydrographic datawere quality checked, then archivedinto yearly files. While hydrographicdata varied in spatial and temporalcoverage, an interval of three months appeared to produceconsistently useable climatologies. Climatologies were createdby interpolating three months of observed hydrographyto the standard grid using the OAX5 optimal-analysisapplication. OAX5 alters the weighting factors of nearestneighbors relative to the shape of the bathymetry, producingmore physically reasonable solutions.The specific methods for each set of analyses are providedin the sections below.4-Northwest Atlantic Marine Ecoregional Assessment • Phase 1 Report