Transcript Sediment Transport in Hurricane Sandy: Glider Observations and Regional Ocean Modeling

Sediment Transport in Hurricane Sandy:
Glider Observations and Regional Ocean Modeling
Travis Miles, Scott Glenn, Oscar Schofield, Josh Kohut and Greg Seroka
Rutgers Coastal Ocean Observation Lab
Oceans MTS/IEEE,
St. John’s Newfoundland
September 16th, 2014
Sediment Transport Studies at LEO Site –early 1990’s
Benthic Acoustic Stress Sensor (BASS) Tripod
Storm-driven sediment transport in M assachusetts Bay
John C. Warner a, , Bradford Butmana, P. Soupy Dalyander b
a
U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, M A 02543, USA
b
Integrated Statistics, 16 Summer Street, Woods Hole, M A 02543, USA
Received 3 November 2006; received in revised form 12 June 2007; accepted 27 August 2007
Available online 22 September 2007
Regional Ocean Modeling
System (ROMS) and Coupled
Ocean Atmosphere Wave
chusetts Bay is a semi-enclosed embayment in the western Gulf of M aine about 50 km wide and 100 km long. Bottom sediment
sion is controlled predominately by storm-induced surface waves and transport by the tidal- and wind-driven circulation.
Sediment Transport
the Bay is open to the northeast, winds from the northeast (‘Northeasters’) generate the largest surface waves and are thus the
ective in resuspending sediments. The three-dimensional oceanographic circulation model Regional Ocean M odeling(COAWST)
System
model
is used to explore the resuspension, transport, and deposition of sediment caused by Northeasters. The model transports
sediment classes and tracks the evolution of a multilevel sediment bed. The surficial sediment characteristics of the bed are
o one of several bottom-boundary layer modules that calculate enhanced bottom roughness due to wave–current interaction.
e field is calculated from the model Simulating WAves Nearshore (SWAN). Two idealized simulations were carried out to
he effects of Northeasters on the transport and fate of sediments. I n one simulation, an initially spatially uniform bed of mixed
s exposed to a series of Northeasters evolved to a pattern similar to the existing surficial sediment distribution. A second set of
ns explored sediment-transport pathways caused by storms with winds from the northeast quadrant by simulating release of
at selected locations. Storms with winds from the north cause transport southward along the western shore of M assachusetts
le storms with winds from the east and southeast drive northerly nearshore flow. The simulations show that Northeasters can
y transport sediments from Boston Harbor and the area offshore of the harbor to the southeast into Cape Cod Bay and offshore
wagen Basin. This transport pattern is consistent with Boston Harbor as the source of silver found in the surficial sediments of
d Bay and Stellwagen Basin.
d by Elsevier Ltd.
Primary validation is post
storm surveys and limited point
measurements.
Need for new technologies for
regional in situ validation
Sediment transport; Three-dimensional numerical model; Storms; Northeasters; M ultiple grain sizes; USA; Gulf of M aine; M assachusetts Bay
duction
ransport and fate of particles is important for
anding of a wide range of issues in the coastal
uch as the fate of contaminants, delineation of seabitat, and long-term change of the sea floor. Over
25 years, observational and modeling studies have
d surface waves, tidal currents, and wind-driven
s as significant processes causing sediment transport
inental shelves (Butman et al., 1979; Drake and
ne, 1985; Wright et al., 1994; Cacchione et al.,
associated with surface waves (Grant and M adsen, 1979)
cause sediment resuspension, while advection by winddriven, density-driven, and/or tidal currents cause net
transport. I n areas of complex coastline, topography, and
sediment characteristics, understanding of long-term sediment fate is difficult with observations alone. Numerical
sediment transport modeling provides the capability to
examine idealized case studies and realistic scenarios to
explore the contributions of various processes with detailed
spatial and temporal resolution. Shelf sediment-transport
models have been applied in two dimensions (cross shelf
Glider Observations of Sediment
Resuspension in a Middle Atlantic Bight
Fall Transition Storm (Glenn et al., 2008)
Temperature
Optical
Sensors
Northeaster – November 2003
Temperature
Broader regional
perspective
Full water column
High Vertical and temporal
resolution
Backscatter 470 nm
This Study:
1.Deploy a glider in rapid response to a
forecasted Nor’easter or Hurricane.
2.Ground-truth sediment resuspension and
transport in the Regional Ocean Modeling
System (ROMS)
RU23: Shallow G1 Slocum Glider
100 meter pump:
Conductivity Temperature
and Depth (CTD) (Seabird)
Optical Backscatter: Wet Labs Ecopuck BB3 (470, 532, 660 nm) –
Smaller particles
Acoustic Backscatter/Currents:
Nortek Aquadopp Current Profiler (2
MHz head, 1 meter bins, internally
logging, 30 days) – medium sands
• Rutgers ROMS ver. 645 on the ESPreSSO domain
• Detailed at : http://www.myroms.org/espresso/
• Cape Hatteras to Cape Cod
• 36 Vertical Levels, 5 km resolution, output hourly
• Tides at boundary from ADCIRC
• HYCOM-NCODA Boundary Conditions
• NCEP North American Mesoscale (NAM) 12km – 3 hourly Wind forcing
(Cahill et al., 2008, Haidvogel et al., 2008, Hoffman et al., 2008, Zhang et al.,
2009a,b, Wilkin and Hunter, 2013)
• Rutgers ROMS ver. 645 on the ESPreSSO domain
• Detailed at : http://www.myroms.org/espresso/
• Cape Hatteras to Cape Cod
• 36 Vertical Levels, 5 km resolution, output hourly
• Tides at boundary from ADCIRC
• HYCOM-NCODA Boundary Conditions
• NCEP North American Mesoscale (NAM) 12km – 3 hourly Wind forcing
• Replaced NAM with Weather Research Forecast Model 6 km – hourly
• Coupled Bottom Boundary Layer (SSW_BBL) included in ROMS checkout
• Wave Height, Wave Period, and Wave Direction from NOAA NCEP
Wavewatch III 3-hourly (http://polar.ncep.noaa.gov/waves/)
• Idealized Sediment from the Community Sediment Transport Model
• Version Included in ROMS Trunk
• Two Non-Cohesive size-classes 0.1 mm and 0.4 mm
• Fall Velocities 5.7 mm/s and 52 mm/s, 0.14 and 0.23 Critical Shear
Stress ,respectively
• Spatially uniform for entire Domain
(Warner et al., 2008, Madsen 1994, Styles and Glenn 2000, Wiberg and Harris 1994,
Harris and Wiberg 2001)
Original plan October 20th : Deploy glider and transit across
the shelf waiting for a storm…
October 22nd, 2012
RU23 Deployed on October 25th
Transited southeast along 40 meter isobath
(southern flank of Hudson Shelf Valley)
During storm advected southwestward.
Within ~100 km of storm center NE
quadrant (strongest winds/waves).
Hurricane Sandy
October 29, 2012
NOAA/NHC Damage:
#2 with >$60 Billion.
Minimum pressure – 948 mb
Storm surge over –14 ft. in
NYC
Superstorm Sandy: 2 Days Before Landfall
Superstorm Sandy: 1 Day Before Landfall
Superstorm Sandy: Morning Before Landfall
Superstorm Sandy: Landfall (20:00 Local)
Along-shore
Along-shore
Onshore
Temperature, transitions from 2layer to well-mixed on the 29th at
06:00 GMT 18 hrs before landfall
Strong one-layer flow just prior to
landfall > 1 m/s
Weak Two-layer flow while
stratified: Onshore surface,
offshore bottom ~0.3 m/s
Shear least-squares method: Visbeck et al. (2002) and Todd et al. (2011)
ROMS 0.4 mm sediment
ROMS 0.1 mm sediment
Acoustic Backscatter
Optical Backscatter
Chlorophyll Concentration
ROMS 0.4 mm sediment
ROMS 0.1 mm sediment
Acoustic Backscatter
Optical Backscatter
Chlorophyll Concentration
ROMS 0.4 mm sediment
ROMS 0.1 mm sediment
Acoustic Backscatter
Optical Backscatter
Chlorophyll Concentration
ROMS 0.4 mm sediment
ROMS 0.1 mm sediment
Acoustic Backscatter
Optical Backscatter
Chlorophyll Concentration
ROMS 0.4 mm sediment
ROMS 0.1 mm sediment
Acoustic Backscatter
Optical Backscatter
Summary/Conclusions
1. Model and glider show full water-column sediment
resuspension as Sandy made landfall.
1. ROMS reasonably captures the timing and direction of
sediment transport.
2. Gliders may be essential to supplement traditional
sampling methods for 3D model validation, particularly
in large storms.
1.Full water-column coverage w/ single profiling sensor
Future/Ongoing Work
• Model sensitivities
• Coupled atmospheric and wave model
• Calibrate optical sensors w/ in-situ sediment necessary to make
quantitative comparisons.
• New technologies:
– Wave Sensors – U. of Maine w/ Neal Pettigrew
– Downward looking integrated current profiler
– Glider integrated LISST: Breaking up into grain sizes
• CINAR TEMPESTS project
– 4 Planned deployments next 2 years
• 2 Nor’easters & 2 Hurricanes
• First deployment March 2014
Thank You
Questions?
Thanks To:
Coastal Ocean Observation Lab
Nortek (student equipment grant)
Teledyne-Webb Graduate Funding
MARACOOS – Glider deployments
Nortek Aquadopp Current Profiler:
2 MHz Custom glider head – Upward looking (doesn’t block Optics)
- Instrument pitch reads 0 at glider pitch of 26.5o
10 Meter profile length
- 1 meter bins
- 0.2 meter blanking distance
3 beams – collected in Beam coordinates and transformed to EastNorth-Up during post-processing
Lithium batteries allows for ~30 day deployment, non-integrated
internally logging.
Nortek Aquadopp Current Profiler:
Acoustic Backscatter:
2 MHz head ~0.25 mm
sediment
Lohrman, 2001
Wave Model performs well
Model
Pre- storm
Peak- storm
Post- storm
Optics
Acoustics