Coastal Observation and Prediction Sponsors:

1
Observing Storm-Induced Sediment Resuspension
Processes in the Middle Atlantic Bight with
Slocum Gliders Scott Glenn, Oscar Schofield,
Robert Chant, John Wilkin, Josh Kohut, Janice
McDonnell
Coastal Observation and Prediction Sponsors
2
Phased Deployment and Operation of the
Mid-Atlantic Regional Coastal Ocean Observing
System (MARCOOS) 30 Co-PIs, 20 Institutions
3
Regional Theme 2 Ecological Decision Support -
Fisheries
4
Rutgers Slocum Glider Fleet Missions 140 Glider
Days 1836 Calendar Days 1047 Distance 37,135
km Casts 284,889
Storm Track
Regional Glider Lines
5
Undergraduate Education Halifax Atlantic
Crossing (2008)
6
At Sea with Sandy Williams - 1982 - R/V
Wacoma Coastal Ocean Dynamics Experiment (CODE)
Grant, W.D., A.J. Williams and S.M. Glenn, 1984.
Bottom stress estimates and their prediction on
the northern California shelf during CODE-1 The
importance of wave-current interaction, Journal
of Physical Oceanography, 14, 506-527.
7
Sediment Transport Studies at LEO Site early
1990s
Benthic Acoustic Stress Sensor (BASS) Tripod
Before and After Summer Deployment at LEO
8
LEO Seafloor Cabled Observatory Continuous
Video from the Seabed late 1990s
Lesson The importance of having a continuous
picture to the sea
9
Storm sediment transport on the MAB bight 3-D
models suggest net southward and offshore
transport of material
Wave stress
Deposition (mm)
offshore southward
Keen and Glenn (JGR JPO)
10
Storm sediment transport on the MAB bight 1-D
models observation allow transport to
calculated during storms, net transport is
onshore!
Bottom time series collected
Models parameterized
1-D models of water column and bottom boundary
layer
storms
Significant wave height
Styles Glenn JGR
Styles Glenn JGR
We are getting the sign of the cross shore
transport wrong! Not once but all storms!
Bottom topography
offshore north
onshore south
Styles Glenn JGR
Traykovski JGR
11
Storm sediment transport on the MAB bight 1-D
models observation allow transport to
calculated during storms, net transport is
onshore!
Bottom time series collected
Models parameterized
1-D models of water column and bottom boundary
layer
storms
Significant wave height
Styles Glenn JGR
Styles Glenn JGR
We are getting the sign of the cross shore
transport wrong! Not once but all storms!
Bottom topography
offshore north
onshore south
Styles Glenn JGR
Traykovski JGR
12

• Storm-Induced Sediment Resuspension
• Science Questions
• What differences are observed in stratified
  versus unstratified seasons?
• What processes influence the resuspension of
  sediment?
• What are the implications for the redistribution
  of sediment in the MAB?
• Focus Area
• Mid-shelf region of MAB
• Relatively unexplored
• Broad band of medium grain sands

13

• RU-WRF Forecast of
• Tropical Storm Ernesto
• Improved model physics,
• Higher resolution sst,
• Higher resolution model grids

WRF forecasts the extratopical transition of
Ernesto after landfall
14
Tropical Storm Ernesto Sub-Surface, Outer Shelf
Before
Temperature (ºC)
Backscatter
Before
Temperature
After
During
15
Hurricane Ivan September, 2004 Mid-Shelf
Temperature
Delaware Bay Buoy Storm Peak Conditions Wind
Speed 16 m/s Wave Height 3.8 m Peak Period
8 s
Backscatter 470 nm
16
Northeaster November 2003
Temperature
Delaware Bay Buoy Storm Peak Conditions Wind
Speed 18 m/s Wave Height 3.2 m Peak Period
6 s
Backscatter 470 nm
17
October 2003 Fall Transition Storm - Northeaster
Storm Center Passes Tuckerton - Oct 29 Backside
Westerlies 5 m/s Waves at Delaware Bay - 2 m
Oct 29
B
18
October 2003 Fall Transition Storm - Northeaster
Salinity
Temperature
Backscatter 470 nm
19
October 2003 Fall Transition Storm - Northeaster
Density
Backscatter Ratio (470/676)
Backscatter (470)
20
October 2003 Fall Transition Storm - Northeaster
Local Wave Height
Local Wave Period
Wave Bottom Velocity
Glider Vertical Velocity
October 30, 2003
21
October 2003 Fall Transition Storm - Northeaster
Black Wind Purple Currents Blue Tidal
Current Red De-tided Residual
Suspended Sediment Variability Not Bottom
Sediment Not Waves Not Langmuir Cells Nonlinear
Interaction of Storm Currents, Tides
Waves Currents to the left of the wind
1 2 3 4 5
22
Conservation of Sediment Mass Closure -
Constant Stress Layer, No Stratification
Suspended Sediment Concentration Profile
Fall Velocity / Shear Velocity Ratio
In terms of the Normalized Backscatter
Plot vs.
Find Slope
23
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
24
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
25
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
26
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
27
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
28
s
Blue Density Red Circles Backscatter Used in
Fit
Before Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
29
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
30
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
31
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
32
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
33
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
34
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
35
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
36
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
37
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
38
s
Blue Density Red Circles Backscatter Used in
Fit
After Transition
ln(z/z(1.5m))
ln(bb(z)/ bb(1.5m))
39
October 2003 Fall Transition Storm - Northeaster

• Fall Transition
• BBL Growth
• Rapid Increase in u as stratification is
  lost
• Mixing throughout watercolumn

1 2 3
4 5
RMS
wf/u
October 30, 2003
40
October 2003 Fall Transition Storm - Northeaster
1 2 3
4 5
Total Load
Current Speed
Net Trans- port
October 30, 2003
41

• Conclusions
• Even weak stratification has a significant
  impact on turbulent mixing across boundary layers
• Sediment Resuspension depends on storm currents,
  tides and waves
• Sediment Transport depends on the complex life
  history of each storm
• Glenn, S., C. Jones, M. Twardowski, L. Bowers, J.
  Kerfoot, J. Kohut, D. Webb, O. Schofield,
• Glider observations of sediment resuspension in a
  Mid-Atlantic Bight fall transition storm,
• Limnology Oceanography, in press.
• Future Work
• Turbulence Sensors on Gliders with Oregon State
  University