Join us for a Physical Oceanography Seminar from Dr. Magdalena Andres, Associate Scientist of Physical Oceanography at Woods Hole Oceanographic Institution, titled "The transport and velocity structure of the Gulf Stream downstream of Cape Hatteras."

Abstract: Full-ocean-depth observations of subinertial horizontal velocity, temperature and salinity obtained from subsurface moorings at 68.5° W over the period October 2010 - May 2014 are analyzed in conjunction with altimeter-based sea surface height data to construct estimates of the time-averaged Gulf Stream velocity structure and transport. Construction of the stream-coordinate mean section follows the methods of Hall and Bryden [1985] and Johns et al. [1995] where data from a single mooring (or an array) are first binned relative to distance from the Gulf Stream axis and then averaged.  The moored results are compared with an ensemble of full-depth lowered acoustic Doppler current profiler (LADCP) data collected along the moored array and repeated shipboard ADCP (SADCP) upper-ocean velocity sections occupied upstream at 70.3° W.  A time-averaged, full-depth Gulf Stream volume transport estimate of 93 ± 3 Sv is obtained from the mooring data at 68.5˚W (excluding times of large Stream axis curvature); the corresponding transport based on the LADCP observations is 77 ± 5 Sv (the difference coming principally from flow below 1000-m depth).  Relative to the mean field at 70.3° W, the velocity core of the time-averaged Stream at 68.5° W appears broader with weaker maximum speed and slightly smaller volume transport above 600 m: 55 ± 2 Sv at 68.5° W versus 61 ± 2 Sv at 70.3° W.  Weaker Gulf Stream flow at 68.5° than 70.3° W is also inferred from a stream coordinate analysis of satellite altimeter data.  Possible reasons for these changes with downstream distance are discussed and comparisons to previous analyses of Gulf Stream structure and transport are made.