Applicability of Landsat 8 Thermal Infrared Sensor to Identify Submarine Groundwater Discharge Springs in the Mediterranean Sea Basin

Abstract. Submarine groundwater discharge (SGD) has received increasing attention over the past two decades as a source of nutrients, trace elements and pollutants to the ocean that may alter coastal biogeochemical cycles. Assessing submarine groundwater flows and their impacts on coastal marine environments is a difficult task since it is not easy to identify and measure these water flows discharging into the sea. The aim of this study is to prove the great usefulness of the freely-available thermal infrared (TIR) imagery of the Landsat 8 thermal infrared sensor (TIRS) as an exploratory tool to identify SGD springs worldwide, from local to regional scales, for long-term analysis. The use of satellite thermal data as a technique to identify SGD springs in seawater is based on the identification of thermally-anomalous plumes obtained from the thermal contrasts between groundwater and sea surface water. We propose a conceptual framework to apply this technique worldwide and also discuss the limitations of using this technique in SGD studies. The study was developed on a regional scale in karstic coastal aquifers in the Mediterranean Sea basin at different seasons and diverse meteorological conditions. Although this study demonstrates that the freely-available satellite TIR remote sensing is a useful method to identify coastal springs in karst aquifers both locally and regionally, the limiting factors include technical limitations, geological/hydrogeological characteristics, environmental and marine conditions and coastal geomorphology.