An Annual Cycle of Upper Ocean Salinity in a Rainfall–Dominated Region Captured by High-Resolution Glider Surveys

PI: Luc Rainville, Craig M. Lee, Charles Eriksen, Kyla Drushka
Sponsor: NASA

Contributing to both the Eulerian and Lagrangian components of the SPURS-2 field program, gliders are maintaining a persistent presence though a complete annual cycle, repeatedly occupying survey patterns to resolve the very near-­‐surface layer, mixed layer, and barrier layer. Over a pair of deployments covering an entire year, the main objectives of the SPURS Seaglider program are to:

  1. Resolve salinity, temperature, density, and their lateral gradients, in the top 1000 m of the water column on horizontal scales of ~20 km and time scales on the order of the inertial period (~3 days) near mooring sites(s).
  2. Provide direct estimates of turbulent dissipation in the mixed layer and in the sharp thermocline and halocline, via microstructure measurements.
  3. Provide gradients and turbulence estimates around freshwater patches as they are advected by the mean and mesoscale circulations, in combination with surface drifters or Lagrangian floats.

With these measurements, we will be able to resolve the salt storage and the horizontal and vertical advection of salt, and quantify diapycnal mixing of salt by small-scale turbulence around the mooring(s). This will provide a direct view of the processes by which the ocean spreads and integrates freshwater from precipitation.

The proposed glider surveys will characterize the upper ocean in a consistent, reapeated manner at temporal and spatial scales that are well matched to the footprint and repeat cycle of the Aquarius salinity satellite. The year-long time series will capture an annual cycle to provide ample data for direct comparison with satellite measurements. These data will also be used to assess the ability (and limitations) of using remotely-­‐sensed measurements to quantify selected terms of the large-scale salinity budget.