Quantifying DOC and Its Controlling Factors in Major Arctic Rivers during Ice-Free Conditions using Sentinel-2 Data

Abstract

The six largest Arctic rivers (Yenisey, Lena, Ob’, Kolyma, Yukon, and Mackenzie) drain the organic-rich Arctic watersheds and serve as important pools in the global carbon cycle. Satellite remote sensing data are considered to be a necessary supplement to the ground-based monitoring of riverine organic matter circulation, especially for the ice-free periods in high-latitudes. In this study, we propose a remote sensing retrieval algorithm to obtain the chromophoric dissolved organic matter (CDOM) levels of the six largest Arctic rivers using Sentinel-2 images from 2016 to 2018. These CDOM results are converted to dissolved organic carbon (DOC) concentrations using the strong relationship (R2 = 0.89) between the field measurements of these two water constituents. The temporal-spatial distributions of the DOC in the six largest Arctic rivers during ice-free conditions are depicted. The performance of the retrieval algorithm verifies the capacity of using Sentinel-2 data to monitor riverine DOC variations due to its improved spatial resolution, better band placement, and increased observation frequency. River discharge, watershed slopes, human activities, and land use/land cover change drove much of the variation in the satellite-derived DOC. The seasonality, geography, and scale would affect the correlation between DOC concentration and these influence factors. Our results could improve the ability to monitor DOC fluxes in Arctic rivers and advance our understanding of the Earth’s carbon cycle.

Exploring Spatially Explicit Changes in Carbon Budgets of Global River Basins during the 20th Century

“…The DOC concentrations tend to be higher at high latitudes, especially in the Northern Hemisphere, and the highest DOC concentrations are in Arctic river basins. This agrees with the reported high DOC concentrations for the Yenisey (2–13 mg C/L), Ob’ (4–17 mg C/L), Lena (3–24 mg C/L), Yukon (3–16 mg C/L), Porcupine (2–12 mg C/L), and Kolyma (3–18 mg C/L) Rivers. ,, The latitudinal distribution of river DOC concentrations is mainly due to the spatial heterogeneity of soil C inputs. , High-latitude soils and peatlands account for about half of the global soil C stock, much of which is in the Arctic watersheds that extend as far south as 45°N in the Eurasian continent. , With substantial inputs from the large soil C stocks, ,,− the DOC concentrations in Arctic rivers are among the highest. The DOC concentrations for tropical rivers are low because high DOC inputs (from vegetation and soils) to rivers are balanced by high DOC decomposition rates at high temperatures.…”

“…This agrees with the reported high DOC concentrations for the Yenisey (2–13 mg C/L), Ob’ (4–17 mg C/L), Lena (3–24 mg C/L), Yukon (3–16 mg C/L), Porcupine (2–12 mg C/L), and Kolyma (3–18 mg C/L) Rivers. 87 , 94 , 95 The latitudinal distribution of river DOC concentrations is mainly due to the spatial heterogeneity of soil C inputs. 94 , 96 High-latitude soils and peatlands account for about half of the global soil C stock, much of which is in the Arctic watersheds that extend as far south as 45°N in the Eurasian continent.…”

“…92 Simulated DIC concentrations are also high in rivers in semiarid and arid regions because of the high evaporation and low water discharge, 93 including the Niger and Nile River basins (in northern Africa), Limpopo and Orange River basins (in southern Africa), Darling River basin (in Oceania), and Indus, Ural, Volga, Tigris, and Euphrates River basins (in eastern Europe and western Asia). 87,94,95 The latitudinal distribution of river DOC concentrations is mainly due to the spatial heterogeneity of soil C inputs. 94,96 High-latitude soils and peatlands account for about half of the global soil C stock, much of which is in the Arctic watersheds that extend as far south as 45°N in the Eurasian continent.…”

Landscape, Soil, Lithology, Climate and Permafrost Control on Dissolved Carbon, Major and Trace Elements in the Ob River, Western Siberia

“…Several detailed studies of Dissolved Organic Carbon (DOC) and major elements were conducted at the terminal gauging station of the river, near the Salekhard city [4][5][6]. These included DOC time-series observations by molecular-level techniques [15] and via remote sensing [16] and the quantification of particulate organic matter export [7]. In contrast, spatial coverage of the river main stem and its tributaries remains rather low, with just a few studies of the dissolved carbon and related CO 2 and CH 4 emissions [17,18] and one study of the molecular composition of DOC [19].…”

Landscape, Soil, Lithology, Climate and Permafrost Control on Dissolved Carbon, Major and Trace Elements in the Ob River, Western Siberia

“…Several detailed studies of Dissolved Organic Carbon (DOC) and major elements were conducted at the terminal gauging station of the river, near the Salekhard city [4,5,6]. These included DOC time series observation by molecular-level techniques [15] and via remote sensing [16] and quantification of particulate organic matter export [7]. In contrast, spatial coverage of the river main stem and tributaries is rather low, with just a few studies of the dissolved carbon and related CO2 and CH4 emissions [17,18] and one study of molecular composition of DOC [19].…”