Continental Shelf Break and Continental Shelf Important Processes at the Shelf Break: Shelf Break Fronts Eddies and meanders Intrusions Shelf Break Depth.

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Presentation transcript:

Continental Shelf Break and Continental Shelf Important Processes at the Shelf Break: Shelf Break Fronts Eddies and meanders Intrusions Shelf Break Depth - Ekman Dynamics Property exchange through Canyons

SHELF BREAK FRONTS A hydrographic section through the shelf break front on the shelf of the Mid-Atlantic Bight, taken south of Rhode Island in April After Flagg and Beardsley (1975), adapted from Bowman and Esaias (1978).Flagg and BeardsleyBowman and Esaias © 1996 M. Tomczak

SHELF BREAK FRONTS The shelf break front of Bass Strait. Left: Sea surface temperature (°C, top), salinity (middle) and density (bottom). Right: Vertical density sections across the front, south (top) and north-east (bottom) of the Cascade. As indicated by the and contours, the front is attached to the bottom south of the Cascade but lifted off the bottom, indicating movement down the slope, in the north. The approximate position of the two vertical sections is indicated by the black lines in the temperature map (a). Adapted from Tomczak (1985). Tomczak © 2000 M. Tomczak

EDDIES AND MEANDERS Cause large cross-isobath flows Frontal eddies Small cold-core cyclonic features Enhance shelf/ocean exchanges Meanders

MEANDERS WARM-CORE RINGS COLD-CORE RINGS

Importance of shelf break depth on shelf/ocean exchange

Importance of canyons

Canyons favor injection of ocean materials to coastal environments

Sometimes really close to the coast But they may also serve as conduits of terrigenous materials to the open ocean

Dynamics of Wind-Dominated Shelves (e.g. western coast of U.S.) Across-shelf Along-shelf Across-shelf dynamics: Integrating throughout the water column:

Continental Shelves Influenced by Freshwater (Large Scale) Along-shore Across-shore Semigeostrophic Dynamics Similar to Shallow Shelves

Coherent Coastal Current

Mid-Atlantic Bight

Greenland Norway Iceland

Gaspé Peninsula Québec New Brunswick Nova Scotia Newfoundland

Anticosti Island Gaspé Peninsula Québec

Gaspé Peninsula Québec New Brunswick Nova Scotia Newfoundland What is the transverse length scale? Reformulating in terms of the balance between baroclinic pressure gradient and Coriolis: Scaling: Internal radius of deformation or Internal Rossby radius

Continental Shelves Influenced by Fresh Water (small scale) Non-linear effects may be influential Coriolis not

Radial Plume - Pulsating

Results by Neil Banas, U. of Washington What if wind is important?

ComponentNon- linear CoriolisPressure Gradient Wind Stress Other Stresses Narrow and deep shelves cross-shelf X XXX X along-shelf X XXX X Shallow shelves cross-shelf X XX XX along-shelf XX XX Shelves influenced by fresh water cross-shelf X XX X X (large scale) along-shelf X XXX Shelves influenced by fresh water cross-shelf XX X XX (small scale) along-shelf XX X XX Steady Dynamics Over Continental Shelves XX - Dominant Forcing X - may be dominant X - weak