Ediz Hook, Port Angeles ESCI 321 announcements
• Problem set 2 due tonight at midnight • Exam 2 in one week • We will have a major review session next Thursday. Come with questions. • Study guide posted. Bring to class on Thursday
I. Coast formation
II. Beaches: Rivers of sand
III. Estuaries
http://www.nps.gov/olym/naturescience/damremovalblog.htm
1 Processes determining coastal morphology and formation Beach morphology Plate tectonics Sea level changes (eustatic and relative sea level change) Glaciers Weathering Wave action and storms
Maine N.C. General scheme of coastline development (primary → secondary)
Seasonal changes in beach morphology Longshore sediment transport
How do waves affect beaches? (Beach movie)
2 Tombolo on the shore of Lake Erie, Erie, Pennsylvania
Formation of rip currents and beach cusps Sediment composing barrier Islands along the east coast of the U.S. is continuously eroding and depositing toward the continent and toward the south.
Swash on beach cusps at Propriano, Corsica. (Photo: Sogreah, France) Rip currents on a New Zealand beach
3 Dune Ridge Beach Open Ocean Puget Sound coastlines Lagoon Marsh Flat
Lagoonal Peat
Common types of shorelines in Puget Sound Natural shoreline with development
•Sand and gravel •Sandy beach/dunes •Sediment-starved beach •Mudflats •Deltas •Beach w/ bulkheads
4 Shoreline with bulkhead
Effects of beach armoring on amphipod habitat, Paihia, New Zealand
Forage fish spawning grounds in Bellingham Bay • Surf smelt spawn in upper intertidal zone • In Bellingham Bay, they spawn only in a few spots • All other shorelines in the bay have bulkheads or seawalls
Surf smelt and sand lance spawning areas in Bellingham Bay
5 Estuarine circulation is determined by the relative importance Estuaries of freshwater input (causing stratification) and tidal mixing Estuary definitions: (Pritchard 1952) A semi-enclosed coastal body of water that has a Salt-wedge estuary: free connection with the open sea and within which sea water is High freshwater flow rate measurably diluted with fresh water derived from land drainage.
Well-mixed estuary: (Fairbridge 1980) an inlet of the sea reaching into a river valley as High rate of tidal mixing far as the upper limit of tidal rise.
Importance: Partially-mixed estuary: Productivity, habitat, nursery grounds, pollutant filters, Intermediate conditions great flat spaces for development
Fjord with sill: inhibits inflow
Two types of pressure gradients Pressure gradient terms
• Barotropic (sea surface slope) • Barotropic fields • Baroclinic fields • Baroclinic (density variation, sloping isopycnals) Isobars and isopyncnals parallel Isobars and isopyncnals inclined • Components of flow in estuaries
Sea surface Isobar Isopycnal Level surface
6 Estuarine circulation with sills Effect of coriolis (SJF cross section) Northern shore Southern shore
Tide
Out
In
Thompson 1994 Rossby radius: velocity/Coriolis, or u/2Ωsin(φ) ≈ (0.2 m/s) / ((2*10-5 s-1) ≈ 10 km
Calculating rates of estuarine mixing, Circulation in Puget Sound flushing time and residence time S V V • Puget Sound divided into basins by sills T i R T T R FT surf RT deep O O i • Sills increase mixing and reduce mean Si SO TO Ti Surface water Bottom water circulation rates & exchange among basins
7 Modeled currents in southern PS Links to other model output
• http://faculty.washington.edu/pmacc/MoSS ea/movies/SSS_daily_salish.mov • http://faculty.washington.edu/pmacc/MoSS ea/movies/SSS_hourly_salish.mov • http://pugetsound.pnnl.gov/
DOE SPS model
“Two-layer” system: What are the PS basin circulation layer depths?
Strickland 1983
8 Basins of Puget Sound
Depth of no motion Whidbey Basin
Admiralty inlet
Main Basin Possession Sound: 25m
Main Basin: 80m Hood Canal
South Sound
Estuarine circulation summary Next project
• Circulation determined by balance of tides and river inflow • Nitrogen budget for Bellingham Bay • Instantaneous velocities: Due to tides (barotropic P) • Due November 28th • Average (residual) velocities: Due to river flow. • Assignment posted on canvas site Outflow – Barotropic pressure gradient. Inflow – Baroclinic pressure gradient. • Average circulation can be calculated from data on river flow and salinity. • Sills separate basins of Puget Sound, increasing residence time within each basin
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