Dissolved organic matter composition of Arctic rivers: Linking permafrost and parent material to riverine carbon. Issue 12 (19th December 2016)

• Record Type: Journal Article
• Authors: O'Donnell, Jonathan A.; Aiken, George R.; Swanson, David K.; Panda, Santosh; Butler, Kenna D.; Baltensperger, Andrew P.
• Is Part Of: Global biogeochemical cycles. Volume 30:Issue 12(2016:Dec.)
• Page Start: 1811
• Page End: 1826
• Publication Date: 2016-12-19
• Subjects: Arctic -- dissolved organic matter -- permafrost -- carbon cycle -- rivers -- climate change; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/2016GB005482
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high‐latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine‐grained loess compared to watersheds underlain by coarse‐grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice‐rich landscapes compared to rivers draining ice‐poor landscapes. Similarly, specific ultraviolet absorbance (SUVA254, an index of DOM aromaticity) values were highest in watersheds underlain by fine‐grained deposits or ice‐rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA254 were negatively correlated with watershed active layer thickness, as determined by high‐resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM. Key Points: DOM composition varies across Arctic rivers in northern Alaska Parent material and ground ice content drive spatial patterns of DOM DOC concentration and aromaticity are negatively correlated with watershed active layer thickness