Post on 31-Jan-2016
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Connecting the sound to the shelf:
a numerical modeling study of estuarine exchange flow
in the Salish Sea
Dave Sutherland1
Parker MacCready1, Neil Banas2
1 School of Oceanography, UW2 Applied Physics Laboratory, UW
CERF, Portland, OR, November 2009
Connecting the sound to the shelf:
a numerical modeling study of estuarine exchange flow
in the Salish SeaAcknowledgments:PRISM (Jeff Richey)
Barb Hickey, Amy MacFadyen, David Darr (UW)
WA DOE
All data sources
PRISMPuget Sound Regional Synthesis Model
The Salish Sea
Strait of Georgia
Strait of Juan de Fuca
Puget Sound
Columbia River
Vancouver
Island
coastal WA
, OR
400 m
The Straits
Strait of Juan de Fuca
• 100 km long, 20 km wide, 200 m deep• ~0.2 Sv exchange flow• significant spring/neap variability,seasonal variability, and tidal rectification(see Martin and MacCready, 2009)
(Collias et al., 1974)
Strait of Georgia
• Fraser River: mean ~7500 m3/s, large seasonal variability
• intense mixing in SJI’s and sill regions, more stratified in basins
• significant spring/neap variability
(Masson and Cummins, 2000)
Salinity, JulySalinity, July
Puget Sound
Skagit2 largest rivers (~75% of Puget Sound mean ~1000 m3/s)
Tacoma Narrows
Admiralty Inlet
Deception Pass
Hood Canal
Snohomish
5 km
Main Basin
SouthSound
WhidbeyBasin
Puget Sound
exchange flow
Salinity, July
Puget Sound
• series of reaches (basins) connected by shallow sills• 0.04 Sv exchange flow• ~1000 m3/s river input• large seasonal and spring/neap variability• residence times: range from 5-70 days
(cm/s)
150
m
MainBasin
HoodCanal
Hypothesis: Puget Sound, SJdF, and the SoG are characterized by quiescent reaches (e.g. Main Basin) and turbulent sill regions (e.g. AInlet)
river river
sill
• Construct realistic hindcast simulations for 1998-2008 in Puget Sound and greater Salish Sea region
• Puget Sound resolution ~200 m• coastal resolution ~2 km• use best available forcing (rivers, meteorological, boundary)
Tool: realistic ROMS numerical model setup of the Salish Sea to investigate patterns of exchange flow on varied time and space scales
(Ebbesmeyer and Barnes, 1980; Cokelet and Stewart, 1985)
Model Set-upParameters- stretched, spherical grid with 25 vertical levels, b = 0.6 and s = 5- k- version of GLS turbulence closure- horizontal diffusivity = 0.5 m2 s-1
- quadratic bottom friction, Cd = 0.003- hmin = 4 m, rmax ~ 0.7, no wet/dry
ForcingBoundaries - Radiation and nudging at southern and western boundaries (NCOM-CCS)
Atmosphere - Bulk fluxes from hourly fields from the MM5 regional forecast model
Rivers - 19 rivers, daily time series (USGS)
Tides - 8 constituents calculated from TPXO7.1 global tide model
Model validation
Whidbey Basinmid Straitof Georgia
JEMSSJDF
ROMSOBS
Mooring time-series outside Columbia
CTD profiles
Patterns of exchange flow
JdF-EJdF-mid
JdF-W
SoG-N
SoG-mid
SoG-S
AI-N,S
MB
SS
WB
HC
AI-N
(May-July mean)
“in-estuary”
“out-estuary”
|Ue| ~ 20,000 m3/snet Ue ~ 500 m3/s
Patterns of exchange flow
JdF-EJdF-mid
JdF-W
SoG-N
SoG-mid
SoG-S
AI-N,S
MB
SS
WB
HC
AI-N
(May-July mean)
“in-estuary”
“out-estuary”AI-S
Patterns of exchange flow
JdF-EJdF-mid
JdF-W
SoG-N
SoG-mid
SoG-S
AI-N,S
MB
SS
WB
HC
MB-N
(May-July mean)
“in-estuary”
“out-estuary”MB-midMB-S
Patterns of exchange flow JdF
SoG
AI
SOG-N
“in-estuary”
“outestuary”SOG-mid
SOG-S
AI-N
“in-estuary”
AI-S
“outestuary”JdF-E
“in-estuary”
“outestuary”JdF-mid
JdF-W
|Ue| ~ 130,000 m3/snet Ue ~ 6000 m3/s
|Ue| ~ 80,000 m3/snet Ue ~ 5000 m3/s
|Ue| ~ 20,000 m3/snet Ue ~ 500 m3/s
Strait of Juan de Fuca Strait of Georgia Admiralty Inlet
Variability of exchange flow at Adm. Inlet
riverdischarge(m3/s)
N/S winds(m/s)
depth meancurrent (m/s)
exchange flow(1000 m3/s)
“out-estuary”“in-estuary”
Skagit Snohomish
Conclusions• Development underway of
realistic, high resolution simulations of Puget Sound and the surrounding coastal ocean
• Patterns of exchange flow are useful in characterizing estuarine regions in the Salish Sea and will lead to quantitative comparisons in the future
(http://faculty.washington.edu/dsuth/MoSSea/)