Seasonal dynamics of dissolved organic matter in the Mackenzie Delta, Canadian Arctic waters: Implications for ocean colour remote sensing

Increasing air temperatures and associated permafrost thaw in Arctic river watersheds, such as the Mackenzie River catchment, are directly affecting the aquatic environment. As a consequence, the quantity and the quality of dissolved organic carbon (DOC) that is transported via the Mackenzie River i...

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Bibliographic Details
Published in:	Remote sensing of environment Vol. 283; p. 113327
Main Authors:	Juhls, B., Matsuoka, A., Lizotte, M., Bécu, G., Overduin, P.P., El Kassar, J., Devred, E., Doxaran, D., Ferland, J., Forget, M.H., Hilborn, A., Hieronymi, M., Leymarie, E., Maury, J., Oziel, L., Tisserand, L., Anikina, D.O.J., Dillon, M., Babin, M.
Format:	Journal Article
Language:	English
Published:	Elsevier Inc 15-12-2022 Elsevier
Subjects:	Beaufort Sea Dissolved organic matter Environmental Sciences Land-ocean fluxes Mackenzie River Satellite ocean colour remote sensing Sentinel-3 OLCI Sentinel-3 OLCI Beaufort Sea Dissolved organic matter Satellite ocean colour remote sensing Mackenzie River Land-ocean fluxes
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Summary:	Increasing air temperatures and associated permafrost thaw in Arctic river watersheds, such as the Mackenzie River catchment, are directly affecting the aquatic environment. As a consequence, the quantity and the quality of dissolved organic carbon (DOC) that is transported via the Mackenzie River into the Arctic Ocean is expected to change. Particularly in these remote permafrost regions of the Arctic, monitoring of terrigenous organic carbon fluxes is insufficient and knowledge of distribution and fate of organic carbon when released to the coastal waters is remarkably lacking. Despite its poorly evaluated performance in Arctic coastal waters, Satellite Ocean Colour Remote Sensing (SOCRS) remains a powerful tool to complement monitoring of land-ocean DOC fluxes, detect their trends, and help in understanding their propagation in the Arctic Ocean. In this study, we use in situ and SOCRS data to show the strong seasonal dynamics of the Mackenzie River plume and the spatial distribution of associated terrigenous DOC on the Beaufort Sea Shelf for the first time. Using a dataset collected during an extensive field campaign in 2019, the performance of three commonly-used atmospheric correction (AC) algorithms and two available colored dissolved organic matter (CDOM) retrieval algorithms were evaluated using the Ocean and Land Colour Instrument (OLCI). Our results showed that in optically-complex Arctic coastal waters the Polymer AC algorithm performed the best. For the retrieval of CDOM, the gsmA algorithm (Mean Percentage Error (MPE) = 35.7%) showed slightly more consistent results compared to the ONNS algorithm (MPE = 37.9%). By merging our measurements with published datasets, the newly-established DOC-CDOM relationship for the Mackenzie-Beaufort Sea region allowed estimations of DOC concentrations from SOCRS across the entire fluvial-marine transition zone with an MPE of 20.5%. Finally, we applied SOCRS with data from the Sentinel-3 OLCI sensor to illustrate the seasonal variation of DOC concentrations in the surface waters of the Beaufort Sea on a large spatial scales and high frequency throughout the entire open water period. Highest DOC concentrations and largest lateral extent of the plume were observed in spring right after the Mackenzie River ice break-up indicating that the freshet was the main driver of plume propagation and DOC distribution on the shelf. Satellite-derived images of surface water DOC concentration placed the in situ observations into a larger temporal and spatial context and revealed a strong seasonal variability in transport pathways of DOC in the Mackenzie- Beaufort Sea region. •Strong seasonal differences of Mackenzie River plume extent on the Beaufort Sea shelf.•In situ data of fluvial marine transition zone improves DOC-CDOM relationship.•DOC concentrations can be estimated from space with an uncertainty of 20.5%.•Remote sensing reveals distribution of DOC on larger scales and higher frequency.
ISSN:	0034-4257 1879-0704
DOI:	10.1016/j.rse.2022.113327