Continuous Underway Shipboard Measurements of Sea Surface Temperature and Sea Surface Salinity: Lessons From IMECOCAL

Abstract:

The problem of the correct quantification of heat exchange in the ocean-atmosphere interface needs studies of sub-mesoscale processes. The problem has captured the attention of observers, theorists, and modelers. Observers use continuous high-resolution measurements of sea temperature and salinity using navigational drones (Saildrones) and satellite-derived products, among other tools, to study sub-mesoscale processes.

In this work, we build on what we learned in our studies of surface temperature and salinity gradients using Saildrones and satellite-derived products to examine the dataset of these variables taken with a ship-mounted thermosalinograph from the Mexican Research program of the California Current (IMECOCAL, for its acronym in Spanish).

The IMECOCAL program has been conducting oceanographic cruises every three months, since October 1997, in the Southern Region of the California Current-off Baja California, Mexico. The sampling activities include, besides the continuous underway measurements of sea surface temperature and salinity, routine conductivity-temperature-depth casts to 1000 m.

We superimposed the IMECOCAL cruises' trajectories for January, April, July, and October 2011 on maps of sea level, temperature, and chlorophyll derived from satellites. We derived buoyancy and density ratio figures along the cruise trajectories, in such a way that, together with the satellite information, we were able to distinguish the fronts associated with coastal upwellings from the fronts associated with the instabilities of the mesoscale activity. Among the practical results found, it is noteworthy that we located the most active coastal upwelling regions along the Baja California peninsula and its seasonal variation associated with 2011.