Mapping Atmospheric Exposure of the Intertidal Zone with Sentinel-1 CSAR in Northern Norway

The intertidal zone (ITZ) is a highly dynamic and diverse coastal ecosystem under pressure that provides important eco-services. Being periodically water makes it challenging to monitor, the only possibility map in all tidal stages by using dense time series of observations. At high latitudes, Sentinel-1 (S1) constellation European Copernicus Program consistently radar imagery at fixed times on near-daily basis, independently cloud cover sunlight. As tides have period 12 h 25.2 min, 1–2 year long S1 are therefore able sample whole range and, thus, percentage atmospheric exposure ITZ, which an environmental parameter. Tidal reference levels mean high/low spring, neap tide correspond each specific percentiles heights inversely exposure. presented method maps basis purely statistical analyses without need for any gauge data, extracting lines via simple thresholding backscatter images. individual thresholds second, fifth, 25th, 50th, 75th, 95th, 98th percentile image were determined fitting threshold contour situ line GPS tracks collected corresponding five locations around Tromsø Northern Norway. They exposures 98%, 95%, 75%, 50%, 25%, 5%, 2%, respectively. was applied Municipality resulting ITZ map. validation shows low neap, mid, spring mapped with accuracies 93%, 84%, 64%, overall approach should be applicable worldwide.