Long-Term Oceanographic Monitoring in Massachusetts Bay (1989-2006) for Assessment of the Transport and Fate of Sediments and Associated Contaminants

FIELD PROGRAM: Sequential deployments of instruments at two sites to measure ocean currents, temperature, conductivity, turbidity light transmission and other parameters was completed between 1989 and 2006 to assess impacts of sewage discharge in Massachusetts Bay. Site A was just at 42 degrees 22.6 minutes N., 70 degrees 47.0 minutes W.; nominal water depth 32 meters. Four mooring configurations were used during the 16-year period (1989-2006) that instruments were deployed at LT-A.  The objective was to obtain measurements of currents and water properties at three nominal depths:  near-surface (about 5 m below the surface, above the thermocline in summer); near-bottom (about 22 m, 10 m above the bottom, below the thermocline in summer); and bottom (1-2 m above bottom). Long -term site B (1997-2004) was at 42 degrees 9.8 minutes N., 70 degrees 38.4 minutes W.; nominal water depth 22 meters. Observations at LT-B included temperature and conductivity at about 12 m (10 m above bottom) and 21 m (1 m above bottom), and time-series sediment trap at about 18 m (4 m above bottom). The instruments at each site varied with what was available at the time, thus current measurements were made at discrete depths with Vector Measuring Current Meters (VMCM) in the early years and progressed to full water column measurements made with Acoustic Doppler Current Profilers (ADCP) after 1994. For a more complete description of the configuration, see the Field Program section of: http://pubs.usgs.gov/ds/74/.

DATA PROCESSING Data processing was conducted using the proprietary software for each instrument, and (or) specialized software developed by the USGS. The proprietary software was often used to download data from the instruments and export the data to ASCII-files. Post-processing of the raw binary or ASCII files was accomplished using USGS software developed in the MATLAB (http://www.mathworks.com/) programming language. As part of the processing, instrument-specific formats were converted to the EPIC-standard NetCDF format (http://www.pmel.noaa.gov/epic/) and scientific units. Data were carefully checked for inconsistencies, time drift, and other problems and then edited if needed. The beginning and end of each data series were truncated to remove data collected out of water. After final editing, the best basic version of the data file that includes all variables recorded at the basic sampling interval (the fastest rate at which the sensor sampled) is published. Biological fouling often degrades light transmission data after several months of deployment. Organisms grow on the transmissometer lenses and gradually block light transmission, which results in a gradual increase of the beam-attenuation coefficient. This drift occurs more quickly and is more severe at shallower depths. The attenuation data plots have not been corrected for biological fouling and should be interpreted with care. Salinity measured by instruments on tripods during 1989-1996, were erroneously low by as much as one practical salinity unit by the end of the 4-month deployments, due to fouling of the conductivity cells. Tripod conductivity data apparently were affected by a slow, gradual build-up of a biological film on the electrodes and also occasional sudden depositions of a significant volume of material (possibly sediments) inside the measurement volume of the conductivity cell. In June 1996 (mooring 470), Sea-Bird pumps were added to the MIDAS to flush the conductivity cell prior to making a measurement, reducing the effect of deposits on the conductivity measurements. The salinity data should be used and interpreted with care. For a more complete description of the data processing, see the Data Processing section of http://pubs.usgs.gov/ds/74/.

Edits to the metadata were made to fix any errors that MP v 2.9.32 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). The links to the experiment page had to be fixed in the Identification_Information section and the Distribution_Information section. Fixed the online link to a cross-reference. Removed special characters in the text. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.