A Remote Sensing Perspective on Spatial Scales of Variation in Biogeophysical Properties of Coastal Waters

Using remote sensing for understanding the effects of environmental changes and anthropogenic activities on estuarine and coastal waters requires the capability to measure and track complex biogeophysical and biogeochemical processes in water. A key sensor design consideration is the minimum spatial resolution required to optically resolve estuarine and coastal features and processes that are of interest. Quantitative information on spatial scales of bio-optical variation in near-shore waters and the expected ability to capture this variation at various spatial resolutions would provide a valuable and essential guideline while deciding on the spatial characteristics of a future remote sensor. We have analyzed continuous, along-track measurements of temperature and salinity of water and absorption and scattering properties of in-water constituents collected using flow-through instruments (AC-9, AC-s) deployed from a ship, airborne lidar, and airborne and spaceborne hyperspectral sensors from various coastal regions around the United States. We analyzed the sub-pixel variability of the aforementioned parameters as a function of spatial sampling interval to quantitatively understand the trade-off between the spatial resolution of a sensor and the in-water spatial variability captured, and look for ‘tipping points’ in the relationship. In general, decreasing the resolution to less than 200 m offered significant gains in spatial information, whereas changes in the spatial resolution beyond the 200-500 m range resulted in only moderate changes in the amount of spatial information captured.