Transcript Robert-Mid-Atlantic Bight

Mid-Atlantic Bight
Transport over a Long Shallow Shelf
The Shelf
~ 25m depth at the
inner shelf
~ 50m at midshelf
~ 200m at the shelf
break, where it then
drops rapidly to deep
ocean
(1 Degree Longitude ~ 85.4km @
40N)
The distance shore to shelf
break ranges from 60-200km
Estuaries of the MAB
Chesapeake Bay system
Delaware Bay
Hudson River
Winter Conditions
Summer Conditions
(Immediately before and during Irene)
Ekman vs Tilburg
Unconventional Upwelling
Tilburg's Model
K_M - vertical eddy viscosity
K_H - vertical eddy diffusivity
Density taken from the Equation
of State
Salinity is constant
Horizontal eddy viscosity and
diffusivity are constant
K_M terms calculated for surface
wind stress and bottom stress
given by D
L= 65km (width of shelf)
Downwelling and Onshore
Transport - Ekman
Downwelling and Onshore
Transport - Tilburg
Transport in 3 Dimensions Wind Stress
Wind Stress is the primary mechanism for transport.
Integrated continuity equation can be used to
demonstrate the surface and bottom stress is directly
related to across shore transport while inversely related
to along shore divergence.
Transport in 3 Dimensions Buoyancy as an amplifier
Shallow Shelf allows for fresh water intrusions to reach
the bottom instead of forming a lens.
Supports geostrophic, cyclonic flow of high downshelf
velocity.
High shear across shore.
These intrusions become displaced offshore and mix
while the region experiences upwelling at the coast.
Transport in 3 Dimensions Buoyancy as an amplifier
The buoyancy intrusion's flow is driven by
stratification gradients (dN^2/dy) creating
velocity gradients along shore.
Negative gradient indicates convergence with the
intrusion upshelf.
Positive gradient indicates divergence with the
intrusion downshelf.
While wind dominates the buoyancy intrusion
under strong wind conditions, divergence may still
be strong under light wind conditions.
References
Across-Shelf Transport on a Continental Shelf: Do Across-Shelf Winds Matter?
Tilburg 2003
Three-Dimensional Flow in a Shallow Coastal Upwelling Zone: Alongshore
Convergence and Divergence on the New Jersey Shelf
Tilburg and Garvine 2003
Additional Images from:
RUCOOL glider page
http://cmtt.tori.org.tw/data/App_map/Maps_jpg/4_13_Mid_Atlantic_Bight_
New_York_Bight.jpg
http://ocw.mit.edu/resources/res-12-000-evolution-of-physicaloceanography-spring-2007/part-1/wunsch_chapter7.pdf