A High-Performance, Fully Encapsulated, Optics-Based Ocean Salinometer

Because salinity is an essential ocean variable whose distribution in time and space is critical to ocean and climate dynamics, in situ salinity measurements are of immeasurable value to numerous oceanographic enterprises. However, like any such measurement, salinity data is in short supply due to the expense and challenge of obtaining measurements, as well as the innate sparseness of point measurements. Thus, there is space for additional sensing capabilities. This effort is an exploration of a viable, optics-based sensor configuration that utilizes Total Internal Reflection (TIR) - the same phenomenon exploited by handheld refractometers and commercially available refractive salinometers such as those employed for aquarium maintenance. The difference in this approach from existing ones is to encapsulate the sensor components in a compact, fully integrated package that lends itself to operating in the harsh ocean environment. Additionally, this small size form factor readily lends itself to integration as a persistent, multi-node array capable of rapid and simultaneous measurements with performance levels comparable to the most trusted oceanographic sensors currently in use. What's more, the compactness, flexibility, and sensing modality enable arbitrary spatial sampling - down to centimeter spacing - and instantaneous profiles. These attributes, and the potential salinity sampling sensor networks they enable, have the potential to unlock as yet unobserved phenomena in ocean dynamics.