The need for surface salinity observations has been expressed in several forums: climate predictions, seasonal to decadal climate variability research, model assimilation, flux closure, hydrologic budgets, and coastal and littoral zone dynamics. Recent studies indicate that ENSO predictability is measurably improved with the proper initiation of salinity fields in forecast models. Salinity also has a major influence on the dynamics of buoyancy-driven coastal jets and currents and serves both as a tracer and index of flow strength. Salinity observations by autonomous systems have been difficult because of conductivity sensor biofouling causes post-calibration uncertainties, and expensive because including a salinity sensor as a stand-alone instrument requires duplicating system components already present in the host: electrical power, computational power, and case. This proposal addresses the development and testing of a novel combination of mechanical systems and chemical treatments that will insure calibration stability for both coastal and open ocean applications, and that permit the deployment of salinity sensors on autonomous surface drifting buoys for observational programs exceeding one year. We look to achieve this goal, at a small incremental cost (<$2K), for our GPS-locating buoys that can be deployed in varied experiments.
Potential Commercial Applications:Clearwater Instrumentation, Inc is a supplier of sophisticated, multi-sensor buoys to oceanographers and meteorologists. Development of a long-lived sea surface salinity sensor will be an important addition to other sensors that currently provide long-term, accurate measurements of properties at the ocean surface: temperature, air pressure, wind speed, and ocean color. Our clients have asked for SSS sensors, but are unwilling to include them in instrumentation because their limited life makes many proposed deployments too expensive in relation to the useable data return. Our goal of an effective SSS sensor for ~$2K will bring this sensor into the realm of what can be afforded for a widely used sensor to add to inexpensive autonomous equipment such as the WOCE SVP drifter.
