Internal Wave Energy Budget Studies in the South China Sea
Abstract : We are focused on understanding small-scale processes that influence the ocean's thermodynamic and dynamic properties on the sub-mesoscale (scales less than 10 km). This includes the role of turbulence in modifying the upper ocean temperature and density structure. In the South China Sea, large- amplitude, nonlinear waves force turbulence in the seasonally variable continental shelf region. New observational data is sought for use in characterizing turbulence phenomena, and for parameterizing processes in models.
Turbulent dissipation on the margins of the South China Sea
[1] Measurements of turbulence along the continental slope, shelfbreak, and shelf of the northern South China Sea are presented from a 10-day measurement program during April 2005. The shelfbreak region was characterized by a deep stratification that appears to be typical of the late winter-monsoon. This appears to shift the wave field at the shelfbreak from the soliton-like depression anomalies observed in previous years to a more complex wave field, supporting high-frequency waves in both upper and lower depth-intervals of the water column. On average, 30% of the depth-integrated turbulent dissipation occurs within 10 m of the bottom, where baroclinic energy is preferentially dissipated. Dissipation levels, reaching 50 mW/m2, are an order of magnitude larger than those attainable through frictional dissipation of the local barotropic tide, and an order of magnitude larger than levels typical in the open ocean.
The potential vorticity flux through the Yucatan Channel and the Loop Current in the Gulf of Mexico
Two‐year‐long time series of current and density structure measurements across the Yucatan Channel's main section allow the calculation of the time‐dependent potential vorticity flux between the Gulf of Mexico and the Caribbean Sea, which is characterized by alternating periods of positive (cyclonic) and negative (anti‐cyclonic) vorticity influx. Periods of negative cumulative vorticity influx are related to the Loop Current extending into the Gulf of Mexico, whereas periods of positive cumulative vorticity influx relate to a Loop Current retraction, sometimes coincident with the shedding of an anti‐cyclonic eddy.