2022 CSDMS meeting-062
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River ice affects the residence time of soil organic C when rivers migrate through permafrost
Josie Arcuri,
(she/her/hers),University of Colorado Boulder Boulder Colorado, United States. Josephine.Arcuri@colorado.edu
Rivers are fundamental sculptors of Earth’s surface, even in the coldest regions where ice seasonally occupies channels. On the North Slope of Alaska, rivers move water and sediment through a treeless, thawing landscape of continuous permafrost. As permafrost thaws, the greenhouse gas emission from soil organic (SOC) decomposition presents a potential acceleration to global warming. Rivers are the main conveyor belt which partitions soil organic carbon (SOC) in thawed river banks between storage and the atmosphere. Bank migration limits C02 respiration from permafrost by decreasing the residence time of SOC in floodplains, but also exposes POC_petro from eroded SOC to in-channel oxidation as sediment is rerouted downstream. Currently, we do not have an understanding of how carbon is exchanged between river banks and running water under the seasonal influence of ice. Untangling how icy rivers reroute SOC is central to assessing if icy landscapes are net sources or sinks in our global carbon budget. Initially, we are looking at characterizing how much SOC is mobilized by river bank erosion and bank collapse from thaw. This is done by creating bank migration maps from remote sensing data to measure rates of bank channel migration along the Canning River, AK. We also look to remote sensing for a record of river ice conditions in relation to the five years of daily mean discharge data from the USGS. We hope to extract a record of locations along the river where (1 ) river ice is prominent, (2) bank migration is overpredicted by classical river bank migration models. Classical river bank migration models depend on bank material properties, channel geometry, and discharge to describe lateral migration. We plan on testing the relationships between predicted and measured migration rates, and river ice occurrence. The knowledge of river ice’s role in bank migration will then be used to inform a model of icy bank erosion. This model considers the effects of lateral migration and bank collapse as a function of excess shear stress and bank stability, but also incorporates a critical discharge to portray the shear-limiting effects of river ice on cross-channel flow. Understanding icy river bank migration is necessary to predict and model the seasonal exchange of carbon between the atmosphere, permafrost floodplains and channel system, and ultimate delivery to the Arctic Ocean. We can also make use of this work in predicting the future contribution of the Canning river watershed, and other arctic landscapes, to the global carbon budget. This work has immediate importance for people who traverse arctic landscapes and depend on their resources, but especially those who live there. Arctic landscape response to climate change is just as much a story about the loss of place and vanishing resources as it is a story about a dynamic earth system.
