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Carbon Dioxide Partial Pressure and Emission Throughout the Scandinavian Stream Network
Author(s) -
Martinsen Kenneth Thorø,
Kragh Theis,
SandJensen Kaj
Publication year - 2020
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2020gb006703
Subject(s) - streams , environmental science , carbon dioxide , hydrology (agriculture) , drainage basin , surface runoff , land cover , flux (metallurgy) , partial pressure , range (aeronautics) , geology , chemistry , geography , oxygen , materials science , land use , ecology , computer network , geotechnical engineering , cartography , organic chemistry , computer science , biology , composite material
Stream networks transport and emit substantial volumes of carbon dioxide (CO 2 ) into the atmosphere. We gathered open monitoring data from streams in three Scandinavian countries and estimated CO 2 partial pressure (pCO 2 ) at 2,298 sites. Most of the sites (87%) were supersaturated when averaged across the year with an overall mean pCO 2 of 1,464 μ atm (range: 17–15,646). Using remote sensing data, we modeled a realistic stream network including streams above ~2.5 m wide and calculated catchment averages of multiple variables associated with geomorphometry, stream network proximity, and land cover. We compared the ability of eight machine learning models to predict pCO 2 and found that the Random Forest model achieved the highest accuracy, with a root‐mean‐square error of 0.22 (log 10 (pCO 2 )) and R 2 of 0.66. Mean catchment elevation, slope, and permanent water cover were the most important predictor variables. We used the predictive model to create a high‐resolution (25‐m resolution) map with predicted stream pCO 2 throughout the 268.807 km stream network in Denmark, Sweden, and Finland. Predicted pCO 2 averaged 1,134 μ atm (range: 154–8,174). We used surface runoff, air temperature, and stream channel slope to estimate gas transfer velocity and CO 2 flux throughout the network. Mean stream CO 2 fluxes ranged from 1.0 and 1.2 in Sweden and Finland, respectively, 3 to 3.2 g C m −2 day −1 in Denmark. Better‐performing models improve our ability to predict pCO 2 in stream networks and reduce the uncertainty of upscaling estimates of carbon emissions from inland waters to countries and continents.