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Melissa Moulton

Research Scientist/Engineer Principal

Affiliate Assistant Professor, Civil and Environmental Engineering

Email

mmoulton@apl.washington.edu

Phone

206-221-7623

Research Interests

Coastal and Nearshore Processes, Environmental Fluid Mechanics, Remote Sensing, Beach Hazard Prediction

Biosketch

Dr. Moulton is a coastal physical oceanographer who studies the dynamics and impacts of rip currents, coastal storms, and inner shelf processes using remote sensing, in situ observations, laboratory experiments, and numerical models.

Education

B.A. Physics, Amherst College, 2009

Ph.D. Physical Oceanography, MIT/WHOI Joint Program, 2016

Publications

2000-present and while at APL-UW

Modeled three-dimensional currents and eddies on an alongshore-variable barred beach

Baker, C.M., M. Moulton, B. Raubenheimer, S. Elgar, and N. Kumar, "Modeled three-dimensional currents and eddies on an alongshore-variable barred beach," J. Geophys. Res., 126, doi:10.1029/2020JC016899, 2021.

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1 Jul 2021

Circulation in the nearshore region, which is critical for material transport along the coast and between the surf zone and the inner shelf, includes strong vortical motions. The horizontal length scales and vertical structure associated with vortical motions are not well documented on alongshore-variable beaches. Here, a three-dimensional phase-resolving numerical model, Simulating WAves till SHore (SWASH), is compared with surfzone waves and flows on a barred beach, and is used to investigate surfzone eddies. Model simulations with measured bathymetry reproduce trends in the mean surfzone circulation patterns, including alongshore currents and rip current circulation cells observed for offshore wave heights from 0.5 to 2.0 m and incident wave directions from 0 to 15° relative to shore normal. The length scales of simulated eddies, quantified using the alongshore wavenumber spectra of vertical vorticity, suggest that increasing wave directional spread intensifies small-scale eddies (O(10) m). Simulations with bathymetric variability ranging from alongshore uniform to highly alongshore variable indicate that large-scale eddies (O(100) m) may be enhanced by surfzone bathymetric variability, whereas small-scale eddies (O(10) m) are less dependent on bathymetric variability. The simulated vertical dependence of the magnitude and mean length scale (centroid) of the alongshore wavenumber spectra of vertical vorticity and very low-frequency (f ≈ 0.005 Hz) currents is weak in the outer surf zone, and decreases toward the shoreline. The vertical dependence in the simulations may be affected by the vertical structure of turbulence, mean shear, and bottom boundary layer dynamics.

Warm and cool nearshore plumes connecting the surf zone to the inner shelf

Moulton, M., C.C. Chickadel, and J. Thomson, "Warm and cool nearshore plumes connecting the surf zone to the inner shelf," Geophys. Res. Lett., 48, doi:10.1029/2020GL091675, 2021.

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28 May 2021

Cross‐shore transport of larvae, pollutants, and sediment between the surf zone and the inner shelf is important for coastal water quality and ecosystems. Rip currents are known to be a dominant pathway for exchange, but the effects of horizontal temperature and salinity gradients are not well understood. Airborne visible and infrared imaging performed on the California coast shows warm and cool plumes driven by rip currents in the surf zone and extending onto the shelf, with temperature differences of approximately 1°C. The airborne imagery and modeled temperatures and tracers indicate that warm plumes exhibit more lateral spreading and transport material in a buoyant near‐surface layer, whereas cool plumes move offshore in a subsurface layer. The average cross‐shore extent of warm plumes at the surface is approximately one surfzone width larger than for cool plumes. Future work may explore the sensitivity of nearshore plumes to density patterns, wave forcing, and bathymetry.

The Inner-Shelf Dynamics Experiment

Kumar, N., and 49 others, including J. Thomson, M. Moulton, and C. Chickadel, "The Inner-Shelf Dynamics Experiment," Bull. Am. Meteorol. Soc., 102, E1033–E1063, doi:10.1175/BAMS-D-19-0281.1, 2021.

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1 May 2021

The inner shelf, the transition zone between the surf zone and the mid shelf, is a dynamically complex region with the evolution of circulation and stratification driven by multiple physical processes. Cross-shelf exchange through the inner shelf has important implications for coastal water quality, ecological connectivity, and lateral movement of sediment and heat. The Inner-Shelf Dynamics Experiment (ISDE) was an intensive, coordinated, multi-institution field experiment from Sep.–Oct. 2017, conducted from the mid shelf, through the inner shelf and into the surf zone near Point Sal, CA. Satellite, airborne, shore- and ship-based remote sensing, in-water moorings and ship-based sampling, and numerical ocean circulation models forced by winds, waves and tides were used to investigate the dynamics governing the circulation and transport in the inner shelf and the role of coastline variability on regional circulation dynamics. Here, the following physical processes are highlighted: internal wave dynamics from the mid shelf to the inner shelf; flow separation and eddy shedding off Point Sal; offshore ejection of surfzone waters from rip currents; and wind-driven subtidal circulation dynamics. The extensive dataset from ISDE allows for unprecedented investigations into the role of physical processes in creating spatial heterogeneity, and nonlinear interactions between various inner-shelf physical processes. Overall, the highly spatially and temporally resolved oceanographic measurements and numerical simulations of ISDE provide a central framework for studies exploring this complex and fascinating region of the ocean.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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