Comparisons of Geostrophic Current Observations from Buoyancy Gliders and Satellite Altimetry

Abstract:

Our ability to estimate surface geostrophic currents in the ocean has improved by the development of autonomous buoyancy-driven underwater gliders and satellite altimetry. In the Gulf of Mexico, it is important to estimate surface current velocities to be able to track large, energetic, anticyclonic eddies that are shed intermittently from the Loop Current. These eddies have the potential to negatively impact the economy of the region by interrupting offshore oil-drilling operations. In this project, we compare geostrophic velocities estimated from gliders and satellite altimetry in the Gulf of Mexico. We seek to quantify the uncertainties of using the two approaches. For this comparison, we will use glider observations gathered by members of the Gulf of Mexico Coastal Observing System (GCOOS) and satellite altimetry data from the Jason-3 mission. Glider data allows density profiles of the water column to be computed to a depth of 1000 meters. These density profiles based on along-track density gradients, are then used to estimate geostrophic velocities perpendicular to the glider transect. Satellite geostrophic velocities, on the other hand, are derived from gradients of sea surface height. By selecting satellite orbital paths nearly parallel to the glider track and extracting satellite data nearly simultaneous with the glider mission, we compare the two cross-track geostrophic velocity estimates. The differences in velocity estimates are quantified and evaluated for statistical significance.