Investigation of vertical and horizontal momentum transfer in the Gulf of Mexico using empirical mode decomposition method

Data from a series of deep mooring stations in the Gulf of Mexico (GOM) have been analyzed with the newly developed empirical mode decomposition and Hilbert spectral analysis method, abbreviated as Hilbert-Huang transformation (HHT). The flows in the GOM near the shelf/slope region are treated as a two-layer system, with the 800-m permanent thermocline as the dividing depth. When the data are treated with HHT, motions of different temporal scales are identified. The top layer (depth less than 800 m) is controlled by inertia flow with episodic Loop Current eddies, while the lower layer (depth greater than 800 m) is controlled primarily by the topographic Rossby waves and small-scale cyclonic and anticyclonic eddies. Using a cross-correlation analysis between the appropriate intrinsic mode components from the data, the wavelength, the phase velocity, and the vertical trapping depth for the topographic Rossby waves were determined. Observations are in general agreement with the modeled results by Oey and Lee.