Quantifying Dissolved Organic Carbon Dynamics Using a Three‐Dimensional Terrestrial Ecosystem Model at High Spatial‐Temporal Resolutions.

Arctic terrestrial ecosystems are very sensitive to the global climate change due to the large storage of soil organic carbon and the presence of snow, glacier, and permafrost, which respond directly to near surface air temperature that has warmed in the Arctic by almost twice as much as the global average. These ecosystems play a significant role in affecting regional and global carbon cycling, which have been traditionally quantified using biogeochemical models that have not explicitly considered the loss of carbon due to lateral flow of water from land to aquatic ecosystems. Building upon an extant spatially distributed hydrological model and a process‐based biogeochemical model, we have developed a three‐dimensional terrestrial ecosystem model to elucidate how lateral water flow has impacted the regional dissolved organic carbon (DOC) dynamics in the Tanana Flats Basin in central Alaska. The model explicitly simulates the production, consumption, and transport of DOC. Both in situ observational data and remote sensing‐based products were used to calibrate and validate the model. Our simulations show that (1) plant litter DOC leaching exerts significant controls on soil DOC concentration during precipitation and snowmelt events, (2) lateral transport plays an important role in affecting regional DOC dynamics, and (3) DOC export to the Tanana River is approximately 9.6 × 106 kg C year−1. This study provides a modeling framework to adequately quantify the Arctic land ecosystem carbon budget by considering the lateral transport of carbon affected by permafrost degradation. The quantification of the lateral carbon fluxes will also improve future carbon cycle modeling for Arctic aquatic ecosystems. Plain Language Summary: Arctic ecosystems are very sensitive to the warming climate because of the presence of snow, glacier, and frozen soil. As Arctic is warming up, snow and glacier are melting, and frozen soil begins to thaw. The latter may release a large amount of carbon stored in the frozen soil, potentially causing a positive feedback to the global climate system. Dissolved organic carbon (DOC) is the largest reduced carbon and plays an important role in the Arctic carbon cycling. Few studies have quantified how land DOC can be produced and released to aquatic ecosystems. In this study, we developed a three‐dimensional ecosystem model to illustrate how DOC can be produced and transferred from land to river. We applied and validated this model to the Tanana Flats in central Alaska. We found that (1) litterfall plays an important role in releasing DOC during snowmelt and runoff, (2) water flow is key to the redistribution of DOC from land to river, and (3) 10,000 tons of DOC is released into the Tanana River annually from this region. Our study provides a powerful tool to quantify the regional carbon cycling by explicitly considering the carbon export from land to aquatic ecosystems in the Arctic. Key Points: A three‐dimensional water and carbon cycle model has been developed and applied to the Tanana Flats Basin in central AlaskaLateral litter DOC and soil DOC fluxes contribute 54% and 46% to the total stream DOC export, respectively, in the Tanana Flats BasinWith plant litter leaching during precipitation and snowmelt events, lateral flow is important in DOC transport from land to aquatic ecosystems [ABSTRACT FROM AUTHOR]