Abstract
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.
Highlights
Climate change is stronger in the Arctic than anywhere else on Earth (Serreze and Barry, 2011): intensified permafrost thaw (Biskaborn et al, 2019), increased river discharge (McClelland et al, 2016) and stronger coastal erosion (Fritz et al, 2017) have significant impacts on the bio physical system
The tuning of the Arctic Nearshore Turbidity Algorithm (ANTA) is based on in-situ measurements from the nearshore waters around Herschel Island Qikiqtaruk (HIQ), located at the Yukon coast in the western Canadian Arctic
The ANTA was applied to Sentinel 2 imagery from Adventfjorden in Svalbard to assess its performance outside the Canadian Beaufort Sea, where the calibration data was collected
Summary
Climate change is stronger in the Arctic than anywhere else on Earth (Serreze and Barry, 2011): intensified permafrost thaw (Biskaborn et al, 2019), increased river discharge (McClelland et al, 2016) and stronger coastal erosion (Fritz et al, 2017) have significant impacts on the bio physical system. Arctic coasts are eroding at a mean annual rate of 0.5 m/a (Lantuit et al, 2013), leading to enhanced sediment input to nearshore areas. These sediments are likely to contain large amounts of carbon given the high organic matter content of coastal permafrost (Fritz et al, 2017).
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