Abstract
In Arctic regions, a major concern is the release of carbon from melting permafrost that could greatly exceed current human carbon emissions. Arctic rivers drain these organic-rich watersheds (Ob, Lena, Yenisei, Mackenzie, Yukon) but field measurements at the outlets of these great Arctic rivers are constrained by limited accessibility of sampling sites. In particular, the highest dissolved organic carbon (DOC) fluxes are observed throughout the ice breakup period that occurs over a short two to three-week period in late May or early June during the snowmelt-generated peak flow. The colored fraction of dissolved organic carbon (DOC) which absorbs UV and visible light is designed as chromophoric dissolved organic matter (CDOM). It is highly correlated to DOC in large arctic rivers and streams, allowing for remote sensing to monitor DOC concentrations from satellite imagery. High temporal and spatial resolutions remote sensing tools are highly relevant for the study of DOC fluxes in a large Arctic river. The high temporal resolution allows for correctly assessing this highly dynamic process, especially the spring freshet event (a few weeks in May). The high spatial resolution allows for assessing the spatial variability within the stream and quantifying DOC transfer during the ice break period when the access to the river is almost impossible. In this study, we develop a CDOM retrieval algorithm at a high spatial and a high temporal resolution in the Yenisei River. We used extensive DOC and DOM spectral absorbance datasets from 2014 and 2015. Twelve SPOT5 (Take5) and Landsat 8 (OLI) images from 2014 and 2015 were examined for this investigation. Relationships between CDOM and spectral variables were explored using linear models (LM). Results demonstrated the capacity of a CDOM algorithm retrieval to monitor DOC fluxes in the Yenisei River during a whole open water season with a special focus on the peak flow period. Overall, future Sentinel2/Landsat8 synergies are promising to monitor DOC fluxes in Arctic rivers and advance our understanding of the Earth’s carbon cycle.
Highlights
Recent observations and climate model projections have identified the Arctic terrestrial ecosystem as a key area for climate change issues
This study demonstrated the capacity of the chromophoric dissolved organic matter (CDOM) algorithm retrieval to monitor dissolved organic carbon (DOC) fluxes in the Yenisei River during a whole open-water season from high spatio-temporal optical remote sensing data
Special attention could be given to the freshet period, where six maps of the DOC concentrations were produced
Summary
Recent observations and climate model projections have identified the Arctic terrestrial ecosystem as a key area for climate change issues. These sensors benefit from daily or weekly resolution, which generally implies more accurate atmospheric corrections Their spatial resolution is too low to evaluate the CDOM and DOC estimations in Arctic rivers. In these ecosystems, high spatial resolution satellite images are required for the following reasons:. This study aimed to evaluate the potential of high spatio-temporal optical resolution remote sensing to retrieve DOC concentrations in the Yenisei River. River based on SPOT5 and Landsat 8 images; (2) evaluate the predictive performance of the developed model to map the CDOM and DOC in the Yenisei River and on other large Arctic river systems; and (3) discuss the potential use of high spatio-temporal remote sensing data to monitor DOC fluxes in Arctic rivers
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