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Spotlight on Sandy

Update on Oceanographic Study Offshore of Fire Island, New York

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The U.S. Geological Survey (USGS) Coastal Change Processes Project is conducting a field experiment on the inner continental shelf offshore of Fire Island, New York, to study the coastal response to storms (see USGS Deploys Oceanographic Gear Offshore of Fire Island, New York). In January 2014, the study team completed a reconnaissance mission during which they measured bathymetry (seafloor depth) and backscatter (data that yield information about seafloor sediment) to determine the best configuration for an equipment array. Between February 3 and 10, 2014, the team deployed eight instrumented tripods at sites with water depths of approximately 12 meters (40 feet), and a specialized wave buoy at a site approximately 25 meters (80 feet) deep. Among the data being collected by the instruments are surface wave heights and directions; ocean current speeds and directions; water levels, salinity, and temperature; near-seafloor turbulence; and suspended-sediment concentrations. The researchers used the research vessel (R/V) Connecticut, which made three separate trips from Woods Hole, Massachusetts, to the deployment area. The gear is principally from the USGS and the Woods Hole Oceanographic Institution.

Data from Coastal Data Information Program (CDIP) buoy 207 showing measurements taken during the February Valentine’s Day storm
Above: Data from Coastal Data Information Program (CDIP) buoy 207 showing wave height (Hs) in meters (m), wave period (Tp) in seconds (sec), and wave direction (Dp) in degrees (deg; north = 0 degrees) during the February Valentine’s Day storm. [larger version]

Recovery of the tripods is scheduled for the end of April 2014. The wave buoy, which will remain on site for several years, is now telemetering surface-wave data in real time to the Coastal Data Information Program (CDIP). The data are being used by the local U.S. Coast Guard Station, local mariners, and tourists. View the data at the CDIP website, buoy 207—Fire Island Nearshore NY , or at the National Data Buoy Center, Station 44094—Fire Island Nearshore, NY—207.

A major storm occurred shortly after deployment—on Valentine’s Day, February 14, 2014—and so expectations are high for interesting sediment-transport data. During this storm, the CDIP buoy recorded wave heights exceeding 4 meters (13 feet) with a 13-second wave period (time between arrival of successive wave crests). The wave direction was initially from the east-southeast and gradually shifted to close to directly onshore, from the south-southeast (see graphs). These variable wave directions during a period of large waves are ideal for testing the hypothesis that the bathymetric ridge and troughs offshore of Fire Island modify incoming storm waves and influence coastal sediment-transport processes.

Numerical modeling results on February 14, 2014, showing wind speed and direction
Above: Numerical modeling results on February 14, 2014, showing wind speed and direction (arrows) and wave heights (color coded) during the storm. Wind speed in meters per second (m/s); size of arrow is proportional to speed. Wave height in meters. [larger version]

The project is also using three-dimensional coupled numerical models to study the interactions of winds, waves, and currents to understand how sediment is mobilized on the seafloor and redistributed during storm events. The modeling system is called Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST; for detailed information, see the article by Warner and others, 2010, in the journal Ocean Modeling). It is a grouping of several publicly available models that have been coupled to allow each specialized component to communicate with the others as part of a larger combined system. This coupling provides for a more realistic simulation of the Earth-systems processes. Model results are displayed in real-time at the Carolina Coastal Change Processes–COAWST webpage.

The numerical models help the project scientists understand how the environment behaves over a large spatial area along the coast. The researchers then compare the model results with observational data to help them validate the model and make sure that the correct processes are being represented in the modeling system. The observations provide a realistic measure of the environment, but are limited to the time that the instruments are deployed. Combining observations and models allows for a more comprehensive approach to understand how natural systems evolve.

Numerical modeling results on February 14, 2014, showing wind speed and direction
Above: Numerical modeling results on February 14, 2014, showing wind speed and direction (arrows) and near-bottom suspended-sediment concentrations (color coded) during the storm. These results can be used to identify coastal locations that are more heavily impacted (and thus have higher concentrations of suspended sediment) by specific storm events. Wind speed in meters per second (m/s); size of arrow is proportional to speed. Suspended-sediment concentration in kilograms per cubic meter (kg/m3). [larger version]

The model results are also helping the researchers understand the complex behavior of sediment movement along the coast. These results are based on a rather coarse model simulation, but they provide a basis for identifying locations along the coastline that are more heavily impacted by particular storms. The scientists can then conduct further investigations by refining the model grid in targeted locations to better understand the conditions at very specific locations. 

Related Sound Waves Stories
USGS Deploys Oceanographic Gear Offshore of Fire Island, New York
Jan. / Feb. 2014
Collecting Ocean-Circulation and Sediment-Transport Data Offshore of Fire Island, New York
July / August 2012

Related Websites
Coastal Data Information Program (CDIP)
CDIP website, buoy 207—Fire Island Nearshore, NY
National Data Buoy Center, Station 44094—Fire Island Nearshore, NY—207
Development of a Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) Modeling System
Ocean Modelling
Carolina Coastal Change Processes

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in this issue:

cover story:

Assessing Climate Change Vulnerability of Pacific Atolls

Spotlight on Sandy
Fire Island Oceanographic Study Update

Linking Coastal Processes and Vulnerability in Assateague Island Region

Recent Hires Assist USGS Barrier Island and Estuarine Studies

EDEN and EVE—Getting the Water Right in Paradise

"Marathon" Bird May Plan Flights Based on Weather Across the Pacific

Warmer Conditions Create New Goose Habitat in Arctic Alaska

25 Years After the Exxon Valdez, Sea Otter Population Rebounds

USGS Intern Teaches Kids about Ocean Acidification

USGS Scientists Support the National Ocean Science Bowl’s Spoonbill Bowl

Communications Awards Recognize Ocean Chemistry Topics

Three USGS Volunteers in Florida Working on Ocean Acidification

USGS Employee in Florida Recognized for Service on Science Museum Board

Publications New Kid on the Web: USGS CMGP Redesigned Website Goes Live

March / April Publications

Accessibility FOIA Privacy Policies and Notices

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