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Near-Inertial and Thermal Upper Ocean Response to Atmospheric Forcing in the North Atlantic Ocean

Katherine E. Silverthorne, Ph.D., 2010
John Toole, Advisor

Observational and modeling techniques are employed to investigate thermal and
inertial upper ocean response to atmospheric forcing in the North Atlantic Ocean. Wintertime enhancement and surface intensification of moored profiler observed near-inertial kinetic energy are recorded. A depth-integrated near-inertial kinetic energy model consisting of a wind forcing term and a dissipation parameterization is shown to have skill capturing the seasonal cycle and order of magnitude of the observations. Focusing on wintertime storm passage, records from drifting profiling floats (EM-APEX) and a meteorological spar buoy/tethered profiler system (ASIS/FILIS) deployed in the Gulf Stream in February 2007 during the CLIvar MOde water Dynamics Experiment (CLIMODE) were analyzed. Despite large surface heat loss during cold air outbreaks and the drifting nature of the instruments, changes in upper ocean heat content were found to be controlled primarily by relative advection of temperature associated with the strong Gulf Stream vertical shear. Gulf Stream velocity records exhibited energetic near-inertial oscillations with frequency that was shifted below the local resting inertial frequency. Three-dimensional Price-Weller-Pinkel (PWP) model simulations show corresponding evidence of near-inertial wave trapping in the Gulf Stream jet and quantify the resulting mixing and its effect on stratification in the Eighteen Degree Water formation region.