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August 19: Devon Kerins: “Climate as the predominate driver for carbon levels in the Rocky Mountains”

Mountains are water towers for billions and are experiencing more rapid warming than lowland places. Although it is known warming will intensify aridity and droughts in these areas, little is known about how chemistry will respond, partly due to scarce and inconsistent temporal data in remote mountains. This work used the space-for-time approach and analyzed long-term average carbon levels across sites of elevation from 965m-3646m in the United States Rocky Mountain region. We focus on dissolved organic and inorganic carbon (DOC & DIC), solutes important as water quality measures as well as indicators of soil respiration and carbon cycles. Both temperature and soil moisture influence their production via soil respiration and their lateral transport can emit notable amounts of CO2 to the atmosphere. Unfortunately, the interrelation between DOC, DIC, and soil respiration is rarely studied, leaving little consensus on how a changing climate may modify DOC and DIC levels. Results show average DOC and DIC concentrations are predominantly regulated by mean discharge and are higher under more arid and warmer conditions. A simple one-box model describing steady state concentration as a function of reaction rate and average discharge captures this trend of increasing concentration with decreasing discharge. Additionally, a positive correlation between concentrations of DOC and DIC among sites implies respiration is likely the main source of both carbon components. Indicating advancing warming, aridity, and drought can lead to higher soil respiration, possibly providing positive carbon-climate feedback. Additionally, the simple model indicates DOC and DIC in mountain streams will likely increase, imposing challenges in water treatment and changes of downstream aquatic ecosystems.

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