Plume Phenomenology 20042006

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Dispersal of the Hudson River Discharge on the
Mid Atlantic Bight Bob Chant, John Wilkin,
Renato Castelao, Elias Hunter, Wiefeng (Gordon)
Zhang, Joe Jurisa, Bob Houghton, Scott Glenn

• Plume Phenomenology (2004-2006)
• Processes involved in dispersion
• Bulge formation
• Wind forcing
• Diurnal
• Low Frequency
• Effects of Ambient Circulation

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LaTTE 2005 Bulge formation and sea breeze.
LaTTE 2004 Coastal current and upwelling
Fong and Geyer (2001) Fong and
Geyer (2002)
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Satellite image (4/27) Drifter track 5/4-5/8
LaTTE 2006 Downstream detachment

• Persistence of feature for gt 1 week
• ADCP Survey (5/2-3) showed off-shore veering jet
  (Joe Jurisa) .
• Formation appears to be associated with
  interaction between bulge and shelf valley
  currents.
• Dye study suggests lateral and along-plume
  straining important to diapyncal mixing processes
  (Bob Houghton).

Winds (m/s)
Despite persistent down-welling winds jet
remained off-shore,
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Outflow tends to form recirculating bulge

• Limits flow to coastal current
• Provides Chemostat for biogeochemical processes
  (Wright et al. Frazer et al, Chen et al. Cahill
  et al. Xi et al.)
• Bulge highly sensitive to winds and ambient
  shelf circulation (Zhang et al. Castelao et al.)

Choi and Wilkin (2007)
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Field data confirmed model results (note color
bar only for ship track salinity not satellite
image)
Field data during weak mean winds
revealed that small fraction (0.3-.05) of outflow
immediately became incorporated in coastal
current. Chant et al. 2008 (JGR). Choi and
Wilkin, 2007 (JPO). Also outflow (and coastal
current) highly responsive to wind forcing even
diurnal. Chant et al. 2008 (JGR). Hunter et
al., 2007 (GRL).
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Outflow configuration shows strong diurnal
variability with sea breeze forcing
12 hours later
Early AM Ebb
Should influence coastal current formation
(Horner-Devine et al. Avicola and Huq)
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Modeled estimate of fresh-water flux in coastal
current Without (top panel) and with (lower
panel) sea-breeze
Eli Hunter (Poster)
Day 12
Moored and wind data during sea-breeze event
Winds
Day 40
Fresh water Flux
Frontal Location (model) Also changes in mixing
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Seasonal Cycle of sea-breeze and River discharge
Sea breeze activity increases during
Freshetboth being related to surface Heating.
Sea breeze occurs 50 of the time during
freshet and throughout summer
Eli Hunter (Poster)
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Interaction with shelf flows
Fong Geyer JPO (2002)
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Seasonal cycle of winds and river flow.
NS winds
EW winds
River Flow
Winds Ambrose Tower (1986-2007) Discharge Cohoes
(1917-2007)
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LaTTE moorings outbut Observatory Marches On!
Discharge
SST
Inner shelf appears more responsive to persistent
upwelling winds. Flow converges at mid-shelf
front producing jet Bulge in Apex feeds
mid-shelf jet Rapid cross-shelf transport
Salinity
Glider Section
Castelao et al. in press (JGR), GRL(2007) Poster
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Response to NW winds.May 24th 2006.
m/s
25 cm/s
Bulge sheared apart by strong up winds currents
in shelf valley. Limits transport to coastal
Current.
Narrow Coastal Current propagates down coast at
(gh)1/2.
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See Gordon Zhangs Poster!!
Red line depicts mean 2005-2006 fresh
water Transport Broad recirculation Off LI
coast Off-shore jet on NJ Coast Broadly
distributed by 100 km down stream and Cut-off at
shelf valley
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Weifeng Gordon Zhang et al (poster)
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Conclusions 1) Hudson outflow tend to favor
Bulge formation. 2) Highly impacted by sea
breeze forcing (Hunter) 3) Influence of low
frequency winds and Ambient shelf circulation
(Jurisa, Castelao, Zhang ,Kohut, Glenn). 4)
Rapid shelf dispersion and seasonal variability
in transport pathways (Castelao, Zhang) 5)
Bulge as Chemostat implications for plume
productivity (Cahill, Frazer, Xi et al.) and
contaminant metal trophic transport pathways
(Wright et al.)
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Eli Hunter Sub-tidal variabitliy in the Hudson
River plume as a result of high frequency forcing
Session 050 Thursday 1730 - 1930
Poster Robert Chen Carbon cycling in the Hudson
River Plume. Session 024 Wednesday 1630
Derik Wright. Trophic transfer of trace metals
in a buoyant river plumeSession 024 Wed945
Robert Houghton Vertical salt flux in a river
plume LaTTE observations vs. gradient
Richardson number calculations Session 024
Wednesday Time 1630 Tom Frazer Phytoplankton
and zooplankton dynamics in a buoyant river plume
. Session 024Wednesday 0900 Weifeng
(Gordon) Zhang. Modeling of freshwater pathways
in the New York Bight. Session 024 Tuesday
1730 - 1930 POSTER Joe Jurisa. Two modes of
Down-shelf freshwater flows off the new Jersey
Coast. Session 159 Wednesday 1615 Yi Xu.
Variability in SST and CHL-a in the New York
Bight spring time in winter? Session 158
Wednesday 1730-1930 POSTER Josh Kohut. Rapid
response of the mid-shelf front to a passing
coastal storm Session 159 Wednesday
1730-1930 POSTER Renato Castelao. Seasonal
evolution of hydrographic fields in the central
middle Atlantic Bight from glider operations.
Seesion 159 1730-1930 POSTER .
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Global distribution of sea breeze (Gille et al.,
2003)
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Putting it all together with 3-year numerical
simulation
Weifeng (Gordon) Zhang poster
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See Jurisa
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