from SMAST (2004)

The Gulf of Maine has a number of key features that are not representable in a global scale climate model. Several of the more important features have been generally described (Gangopadhyay et al., 2002) as:

The Maine Coastal Current.

A buoyancy driven coastal flow originating from the Scotian shelf and fed by river outflow.

The shelf/slope Front.

A frontal boundary separating the cool fresh shelf waters from the warm saline ocean water on the continental slope.

The Jordan Basin Gyre.

A cyclonic gyre in the Jordan Basin of the Gulf of Maine (NE corner, in front of the Bay of Fundy).

The Georges Basin Gyre.

A cyclonic gyre in the Georges Basin of the Gulf of Maine (central, north of Georges Bank).

The Wilkison Basin Gyre.

A cyclonic gyre in the Wilkison Basin of the Gulf of Maine (NW corner, in front of Massachusetts Bay).

A number of regions of tidal mixing fronts and their induced flows

Another review (Brown & Irish, 1992) indicates that the number and direction of the gyres in the Gulf of Maine is more variable. It was decided to

1. Use feature models to create initial estimates of the Maine Coastal Current and the Shelfbreak Front.
2. Use the dynamical model to generate the gyres and tidal mixing fronts.

The feature models provide a semi-analytic representation of the desired structures. The larger scale shelf/slope front proceeds in the following steps:

1. Create an estimate of the shelf conditions.
2. Create an estimate of the slope conditions.
3. Join these 2 estimates across the shelf/slope front.

The feature models fields are then processed for initializing the HOPS PE model. This processing includes:

• Vertical interpolation of the temperature and salinity fields to the HOPS terrain following grid.
• Construction of initial velocity fields from adjusted geostrophic streamfunction.
  1. Differentiate streamfunction to produce adjusted geostrophic velocities.
  2. Vertically interpolating velocities to terrain following grid.
  3. Decomposing interpolated velocities to depth averaged velocity, U₁, and remainder, u'.
  4. Adjusting barotropic velocity so total bottom velocity is parallel to isobaths

     U₂ = U₁ - (U₁+u'_bottom) · gradient(h)/||gradient(h)||

     where

     h is the bottom topography

  5. Taking the curl of U₂ to force a Poisson equation for a transport streamfunction. From this a barotropic velocity, U, is derived with zero divergence of the transport.

Brown, W.S. & J.D. Irish (1992) The Annual Evolution of Geostrophic Flow in the Gulf of Maine 1986-1987. J. Phys. Oceanog., 22, 445-473.

Gangopadhyay, A., A.R. Robinson, P.J. Haley, Jr., W.G. Leslie, C.J. Lozano, J.J. Bisagni & Z. Yu (2002) Feature-oriented regional modeling and simulations (FORMS) in the Gulf of Maine and Georges Bank. Continental Shelf Research, 23(3-4), 317-353.

SMAST (2004) Regional Modeling Activities in the Gulf of Maine/Georges Bank. http://codfish.smast.umassd.edu/research_projects/GB/

Smith, P.C. & J.W. Loder (1991) Physical Oceanography of the Northwest Atlantic Continental Margin. http://www.usglobec.org/reports/rep2/rep2.chapter8.5.html. in "GLOBEC Canada/U.S. Meeting on N.W. Atlantic Fisheries and Climate" Report Number 2. http://www.usglobec.org/reports/rep2/rep2.contents.html.