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Five New USGS Oceanographic Datasets Published Online—Uses Include Assessing Coastal Resilience to Storms
Oceanographic data from U.S. Geological Survey (USGS) experiments off Fire Island, New York; in Barnegat Bay, New Jersey; in the Rachel Carson National Wildlife Refuge, Wells, Maine; on the Chandeleur Islands, Louisiana; and on Dauphin Island, Alabama, were published online in 2014 and early 2015 by the USGS Woods Hole Coastal and Marine Science Center in Woods Hole, Massachusetts. These are “time-series” data—measurements taken at regular intervals over a period of time—and include water temperature, pressure, current velocity, conductivity (salinity), suspended-sediment concentration, and more. These and the other datasets posted at “U.S. Geological Survey Oceanographic Time-Series Data” will help scientists better understand oceanographic and related sediment-transport processes. Knowing how much energy is required to move sediment, and how much energy is produced by storms of varying sizes, permits the development of more accurate planning tools.
Two of the datasets were collected off Fire Island, the first in January–April 2012 to study the effects of storms on coastal erosion and how bathymetry (depth and shape of the seafloor) may function to redirect wave energy. (Read more about this work in “Collecting Ocean-Circulation and Sediment-Transport Data Offshore of Fire Island, New York,” Sound Waves, July/August 2012, and “Coastal Change Processes Project Data Report for Observations Near Fire Island, New York, January to April 2012,” USGS Open-File Report 2014–1159.) This experiment provided valuable information for comparison with data collected after Hurricane Sandy struck the region in October 2012.
The second experiment off Fire Island was conducted February–May 2014 to further study coastal processes that mobilize and transport sediment in the region. Data were collected in the same general area as the 2012 data but closer to shore. (See “Update on Oceanographic Study Offshore of Fire Island, New York,” Sound Waves, March/April 2014, and “Coastal Change Processes Project Data Report for Oceanographic Observations near Fire Island, New York, February through May 2014,” USGS Open-File Report 2015–1033.) This data collection was part of a larger effort by the USGS, in cooperation with the U.S. Army Corps of Engineers and the National Park Service, to study coastal processes on Fire Island and assess coastal change during storms.
The projects in Barnegat Bay and Rachel Carson National Wildlife Refuge were conducted to study circulation and light penetration in estuaries, and how these factors affect vegetation. The Chandeleur Islands and Dauphin Island experiments were conducted to measure wave heights and water levels during storms as part of the Barrier Island Evolution Research (BIER) project.
Data from these experiments, and many more, are on the Woods Hole Coastal and Marine Science Center’s “stellwagen” server in “U.S. Geological Survey Oceanographic Time-Series Data,” a USGS-approved online database of oceanographic time-series measurements recorded during scientific research projects conducted from 1975 to the present. Periods of data collection were typically one month to several years. The experiments commonly focused on observations near the seafloor, but most also obtained current-velocity data in the water column.
Exploring the Data
The main page of the database presents a list of experiments with their dates, organized by region. Each experiment name links to a page with a description of the project, the principal investigator(s), the duration of the experiment, and a map detailing the location of each platform (for example, see “Characterizing light attenuation and sediment resuspension in the Barnegat Bay-Little Egg Harbor estuary, New Jersey”). Also included on the experiment page are links to associated publications and field-activity entries (for example, see Field Activity Report 2013-050-FA ).
Further details of the measurements collected at each site are available in a Google Earth .kml file or in links from a tabular catalog under the heading “Links to the Data.” All experiments have a “basic sampling interval” link to a catalog page describing the observations. Basic-sampling-interval data files contain data reported in the intervals at which they were sampled. Some experiment pages also provide a link to a catalog of all the data files converted to a common time base: hourly averages.
The catalog pages display a table describing the contents of each file: time, location, sample depth, and type of data (for example, see “Fluxes in Barnegat Bay”). Clicking on the filename in the leftmost column initiates downloading of the data file. Viewers such as ncBrowse allow easy viewing of the variables and structure of the files.
Nuts and Bolts
Data served on stellwagen go through a rigorous review and validation process before publication, as described in the database description document at http://woodshole.er.usgs.gov/pubs/of2007-1194/html/dataquality.html. The data are stored in Network Common Data Form (netCDF) files using the Equatorial Pacific Information Collection (EPIC) conventions defined by the National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory. Details about how netCDF is used in the data files are provided at “Network Common Data Format (NetCDF) Storage.” Select datasets have accompanying USGS Open-File Reports describing the research project.
Direct computer-to-computer access to the data files is provided via Unidata’s Thematic Realtime Environmental Distributed Data Services (THREDDS). THREDDS enables access via OPenDAP, WMS, SCS, and other methods.
Discovery by geoportals (webpages that collect information from different sources and provide a single point of access to the information) is enabled by using the attribute convention for dataset discovery (ACDD) in the ISO19115 metadata generated for each file. These records will also be harvested into the USGS Science Data Catalog in the second part of 2015, to become part of the broader list of government-supplied ocean data.
Additional datasets are added to the server as they pass the necessary quality-review steps. Data from several more experiments are in the pipeline as this article goes to press, so check the Oceanographic Time-Series Data website periodically to see what’s new.
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