Practical Applications of Infrared Imagery for Investigating Submarine Groundwater Discharge and Other Thermal Anomalies in Coastal Zones

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Airborne thermal infrared remote sensing is a highly effective tool for mapping locations, surface distributions, and mixing characteristics of terrestrial groundwater discharge to the coastal ocean where even subtle temperature differences exist between the receiving waters and the discharging water. The spatially and temporally variable nature of submarine groundwater discharge (SGD) and its mixing with seawater necessitates rapid, high-resolution data acquisition techniques, of which airborne thermal infrared remote sensing is uniquely qualified. We have used thermal infrared images acquired at 762 m – 2743 m altitude to generate 0.5 m – 3.2 m resolution sea-surface temperature maps with <0.1°C precision and 0.5°C accuracy of most of Oahu, the western half of Hawaii Island, and critical targets on Maui and Molokai. This imagery allows us to precisely locate and map small- to large-scale point-and diffuse sourced groundwater and stream flow discharges not resolvable at the 60 m resolution afforded by Landsat 7 infrared images. These much higher resolutions also minimize contamination effects imparted by land thermal signatures in pixels immediately adjacent to coasts. Basic information about prevailing coastal currents and groundwater mixing with seawater are clearly evident in the images. By establishing several transects across each groundwater plume, the highly precise temperatures in the imagery allow for unique quantification of each discharge plume’s boundary. The surface area of each discharge can then be easily calculated and subsequently up-scaled, or combined with ground-based flow rates to determine time-spatial variations of volumetric flow. This mapping technique is the preferred method for rapid assessment and precise identification of natural and anthropogenically introduced coastal groundwater and stream flow, at scales both large and small. It is highly desirable for many aspects of ecosystems, pollution and coastal-zone planning and management, as well as a prerequisite for the best use of subsequent and time-consuming in-situ field study efforts.


American Geophysical Union Chapman Conference on Remote Sensing of the Terrestrial Water Cycle (AGU)


Kona, HI