Interactions between Biogeophysical and Biogeochemical Processes and their Feedbacks on Permafrost Soil Carbon Stocks
TCS Building 240
The terrestrial northern high-latitude regions above permafrost are considered most vulnerable to climate change, and the dynamics of high-latitude carbon fluxes are likely to have grave impacts on the future global climate. One challenge for more detailed Earth system models is treatment of biophysical and biogeochemical processes and feedbacks, as well as their effects on soil organic carbon (SOC) in the northern high latitudes. This talk will highlight these feedbacks and their impacts on SOC for the northern permafrost region, as estimated by a land surface model — the Integrated Science Assessment Model (ISAM).
Our focus is on recent model improvements in both (1) biogeophysical processes that are important for high latitude soils/snow (the deep soil column, modulation of soil thermal and hydrologic properties, wind compaction of snow, depth of hoar formation, and permafrost SOC) and (2) biogeochemical processes (dynamic phenology and root distribution, litter carbon decomposition rates and residual nitrogen, and soil biogeochemistry). We selected multiple sites for model evaluation and then ran several model simulations to study the effects of feedbacks between biogeochemical and biogeophysical processes on SOC. Our model analysis shows that including biogeophysical processes alone could increase modeled permafrost carbon for the northern high latitudes by about 30%. Also accounting for biogeochmical processes would further improve the soil carbon estimate.