Variations of suspended particulate matter concentrations of the Mackenzie River plume (Beaufort Sea, Arctic Ocean) over the last two decades

This work addresses the last 20 years' evolution of the suspended particulate matter (SPM) concentrations in the Beaufort Sea (Canadian Arctic Ocean) directly influenced by the Mackenzie River discharge. The SPM variations in the coastal zone are highlighted and related to the freshwater and solid discharges of the river measured in situ at the Arctic Red River station (150 km upstream of the river delta). The correlation between the variations of the river discharge and SPM concentration within the surface layer of the coastal waters is obvious. Rather unexpectedly, both have been slightly but significantly decreasing from 2003 to 2018–2019 and started to increase very recently (2019–2022). This change of regime could be explained by changing winter precipitation and groundwater distribution, progressively accumulating sediments within the thawing permafrost layer and its recent release into the groundwater together with thermokarst lakes' rapid drainage. [Display omitted] •We investigated 20-year SPM variations (2003-2022) in coastal waters influenced by Mackenzie River using MODIS/Aqua data•Over the last twenty years, we identified a significant negative trend in both SPM and river discharge from 2003-2018.•We also observed a subsequent positive trend starting in 2019 and continuing to the present.•Offshore SPM variations were linked to Mackenzie hydrology, snow amount, possibly, permafrost over its basin, and wind