Abstract
The ability to track the dynamics of processes in natural water bodies on a global scale, and at a resolution that enables highly localised behaviour to be visualized, is an ideal scenario for understanding how local events can influence the global environment. While advances in in-situ chem/bio-sensing continue to be reported, costs and reliability issues still inhibit the implementation of large-scale deployments. In contrast, physical parameters like surface temperature can be tracked on a global scale using satellite remote sensing, and locally at high resolution via flyovers and drones using multi-spectral imaging. In this study, we show how a much more complete picture of submarine and intertidal groundwater discharge patterns in Kinvara Bay, Galway can be achieved using a fusion of data collected from the Earth Observation satellite (Landsat 8), small aircraft and in-situ sensors. Over the course of the four-day field campaign, over 65,000 in-situ temperatures, salinity and nutrient measurements were collected in parallel with high-resolution thermal imaging from aircraft flyovers. The processed in-situ data show highly correlated patterns between temperature and salinity at the southern end of the bay where freshwater springs can be identified at low tide. Salinity values range from 1 to 2 ppt at the southern end of the bay to 30 ppt at the mouth of the bay, indicating the presence of a freshwater wedge. The data clearly show that temperature differences can be used to track the dynamics of freshwater and seawater mixing in the inner bay region. This outcome suggests that combining the tremendous spatial density and wide geographical reach of remote temperature sensing (using drones, flyovers and satellites) with ground-truthing via appropriately located in-situ sensors (temperature, salinity, chemical, and biological) can produce a much more complete and accurate picture of the water dynamics than each modality used in isolation.
Highlights
Understanding the inter-play of local events and global environmental processes is a frustratingly elusive but critically important goal, as it is fundamental to creating a deeper and more accurate understanding of these processes, and for ensuring that environmental legislation at global and local levels is made on an appropriately informed basis
Study, we we were were interested in exploring whether there was a relationship between water temperature and salinity, salinity, and and whether this would enable temperature to be used as a surrogate means for distinguishing water type in Kinvara Bay
The first step was to establish whether there was a difference between groundwater temperature and sea
Summary
Understanding the inter-play of local events and global environmental processes is a frustratingly elusive but critically important goal, as it is fundamental to creating a deeper and more accurate understanding of these processes, and for ensuring that environmental legislation at global and local levels is made on an appropriately informed basis. For a restricted number of physical parameters (e.g., colour, temperature), global scale sensing can be achieved and dynamics visualised via satellite remote sensing. Satellite sensing has has significant limitations such as Sensors 2016, 16, 1402; doi:10.3390/s16091402 www.mdpi.com/journal/sensors. Sensors 2016, 16, 1402 spatial resolution, low frequency pass-over cycle, inability to track sub-surface events, cloud cover preventing measurements, inability to directly sense detailed molecular information (except for the limited range of species that are directly accessible through spectroscopic methods), and need for specialist knowledge to convert data into accessible (visualized) information. Satellite remote sensing is a very powerful means for accessing information at a global scale, and the capabilities of these platforms continues to improve. The European Space Agency Sentinel 2A satellite launched 23 June 2015, and Sentinel
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