Interactions Between Soil Organic Carbon Concentration and Soil Thermal and Hydraulic Dynamics and Its Impact on Soil Carbon Storage in Northern High-latitudes

Abstract:

Northern high-latitudes (NHLs) regions are estimated to contain half of world’s soil carbon and the dynamics of soil carbon fluxes in these regions will likely impact the global climate. However, the dynamics of soil carbon fluxes in these regions is likely to be significantly altered by increasing temperatures, resulting in a positive feedback on future climate. Processes that are most likely to generate strong carbon cycle feedbacks through redistribution of soil organic carbon (SOC) concentration (e.g., cryoturbation and dissolved organic carbon movement) and subsequently change soil thermal and hydraulic dynamics are poorly represented in Earth system models (ESMs) and thus have not been well-studied. We will present a multi-layer soil biogeochemical model that was implemented into a land surface model, the Integrated Science and Assessment Model (ISAM), to explicitly represent vertical heterogeneity of SOC profiles due to cold region processes and their impacts on soil thermal and hydraulic properties. The newly implemented ten-layer soil biogeochemical model, which extends down to 3.5 meters, includes two types of physical processes for estimating SOC distribution with depth: 1) diffusion, representing SOC movements through bioturbation/cryoturbation, and 2) convection, which describes SOC movements in the liquid phase. Soil type-dependent diffusion and advection rates applied in this model were calibrated and validated using SOC profile data from across the Pan-arctic region. The resulting calibrated and validated coupled model was also driven by future climate projections from CMIP5 output at different sites with varying soil types to study the impact of future climate change on SOC storage.