Observation of the Deepwater Manifestation of the Loop Current and Loop Current Rings in the Eastern Gulf of Mexico

摘要

Following the previous successful observations involving three deployments covering the periods June 2000 June 2002 and April 2003 June 2004, two additional years of deployment of a deep water mooring at the center of the eastern Gulf of Mexico produced additional observations of deep water manifestations of the Loop Current and Loop Current rings. These deployments placed an emphasis on observing the interface between the upper- and lower-layers and variability of water mass properties in deep water. The interface between the upper and lower layers appears to be located close to the sill depth (approx. 800 m) at Strait of Florida. In the modeling component of this project, very high horizontal (.075 degrees) and vertical (100 levels) resolution allowed more realistic representation of the bottom topography including the gentle rise and the steep escarpments. Consequently, it resulted in more realistic simulation of deep water currents in the eastern Gulf of Mexico, i.e., more energetic deep water and more chaotic eddy field in deep water, consistent with the observations at the mooring site. It appears that the Loop Current and Loop Current rings drive deep water currents in the eastern Gulf of Mexico. A modon pair forms underneath the Loop Current when the Loop Current extends northward prior to the formation of a Loop Current ring. However, deep water eddy-eddy and eddy-topography interaction due to the topographic constriction in the central gulf and the limited size of the eastern basin make clear identification of a modon pair problematic. The observations of currents and water mass characteristics at the mooring site appear to be consistent with the Cushman-Roisin et al. (1990) mechanism for the generation of the deep anticyclone-cyclone pair beneath the Loop Current. Another mechanism to transmit significant energy to deep water in the Gulf of Mexico is the barotropic oceanic response to the elevated sea surface near the center of tropical and extra-tropical storms often observed in the Gulf of Mexico. Due to frequent occurrences of these storms within the Gulf of Mexico, this could represent another important forcing mechanism to transmit significant energy to deep water in the Gulf of Mexico, thus contributing to deep water energetics and its well-mixed deep water conditions below the Yucatan sill depths.