Sherman Jeffrey

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  • Technical Report
    The Subduction experiment : cruise report RRS Charles Darwin cruise number 73 subduction 3 mooring deployment and recovery cruise, 30 September-26 October 1992
    (Woods Hole Oceanographic Institution, 1993-03) Trask, Richard P. ; Jenkins, William J. ; Sherman, Jeffrey ; McPhee, Neil M. ; Ostrom, William M. ; Payne, Richard E.
    Subduction is the mechanism by which water masses formed in the mixed layer and near the surface of the ocean find their way into the upper thermocline. The subduction process and its underlying mechanisms were studied through a combination of Eulerian and Langrangian measurements of velocity, measurements of tracer distrbutions and hydrographic properties and modeling. An array of five surface moorings carrying meteorological and oceanographic instrumentation were deployed for a period of two years beginning in June 1991 as part of an Office of Naval Research (ONR) funded Subduction experiment. Three eight month deployments were planned. The moorings were deployed at 18°N 34°W, 18°N 22°W, 25.5°N 29°W, 33°N 22°W and 33°N 34°W. A Vector Averaging Wind Recorder (VAWR) and an Improved Meteorological Recorder (IMET) collected wind speed and wind direction, sea surface temperature, air temperature, short wave radiation, barometric pressure and relative humidity. The IMET also measured precipitation. The moorings were heavily instrumented below the surface with Vector Measuring Current Meters (VMCM), and single point temperature recorders. Expendable bathythermograph (XBT) data were collected and meteorological observations were made while transitting between mooring locations. In addition a series of 59 cm stations were made and water samples taken to be analyzed for tritium levels, salinity and dissolved oxygen content. This report describes the work that took place during RRS Charles Darwin cruise number 73 which was the third scheduled Subduction mooring cruise. During this cruise the second setting of the moorings were recovered and redeployed for a third eight month period. This report includes a description of the instrumentation that was deployed and recovered, has information about the underway measurements (XBT and meteorological observations) that were made including plots of the data, includes a description of the work conducted in conjunction with the tracer/hydrography program and presents a chronology of the cruise events.
  • Article
    Absolute velocity estimates from autonomous underwater gliders equipped with Doppler current profilers
    (American Meteorological Society, 2017-01-31) Todd, Robert E. ; Rudnick, Daniel L. ; Sherman, Jeffrey ; Owens, W. Brechner ; George, Lawrence
    Doppler current profilers on autonomous underwater gliders measure water velocity relative to the moving glider over vertical ranges of O(10) m. Measurements obtained with 1-MHz Nortek acoustic Doppler dual current profilers (AD2CPs) on Spray gliders deployed off Southern California, west of the Galápagos Archipelago, and in the Gulf Stream are used to demonstrate methods of estimating absolute horizontal velocities in the upper 1000 m of the ocean. Relative velocity measurements nearest to a glider are used to infer dive-dependent flight parameters, which are then used to correct estimates of absolute vertically averaged currents to account for the accumulation of biofouling during months-long glider missions. The inverse method for combining Doppler profiler measurements of relative velocity with absolute references to estimate profiles of absolute horizontal velocity is reviewed and expanded to include additional constraints on the velocity solutions. Errors arising from both instrumental bias and decreased abundance of acoustic scatterers at depth are considered. Though demonstrated with measurements from a particular combination of platform and instrument, these techniques should be applicable to other combinations of gliders and Doppler current profilers.