The Arctic Nearshore Turbidity Algorithm (ANTA) - A multi sensor turbidity algorithm for Arctic nearshore environments

The Arctic is greatly impacted by climate change. The increase in air temperature drives the thawing of
permafrost and an increase in coastal erosion and river discharge. This leads to a greater input of sediment and
organic matter into coastal waters, which substantially impacts the ecosystems by reducing light transmission
through the water column and altering the biogeochemistry, but also the subsistence economy of local people,
and changes in climate because of the transformation of organic matter into greenhouse gases. Yet, the quantification
of suspended sediment in Arctic coastal and nearshore waters remains unsatisfactory due to the absence
of dedicated algorithms to resolve the high loads occurring in the close vicinity of the shoreline. In this study we
present the Arctic Nearshore Turbidity Algorithm (ANTA), the first reflectance-turbidity relationship specifically
targeted towards Arctic nearshore waters that is tuned with in-situ measurements from the nearshore waters of
Herschel Island Qikiqtaruk in the western Canadian Arctic. A semi-empirical model was calibrated for several
relevant sensors in ocean color remote sensing, including MODIS, Sentinel 3 (OLCI), Landsat 8 (OLI), and
Sentinel 2 (MSI), as well as the older Landsat sensors TM and ETM+. The ANTA performed better with Landsat 8
than with Sentinel 2 and Sentinel 3. The application of the ANTA to Sentinel 2 imagery that matches in-situ
turbidity samples taken in Adventfjorden, Svalbard, shows transferability to nearshore areas beyond Herschel
Island Qikiqtaruk.