The terrestrial Northern high-latitude (NHL) regions above permafrost are considered to be most vulnerable to climate change, and the dynamics of carbon fluxes in these regions is likely to have tremendous impacts for the future global climate. In this talk, I will investigate interactions of vegetation, soil and snow processes with carbon-nitrogen cycles in the NHL. I will be using the Integrated Science Assessment Model (ISAM), which integrates current advances in modeling of soil biogeophysics and biogeochemistry (including carbon-nitrogen cycles) that are necessary to study the NHL processes. Firstly, I will briefly present the results of model calibration using site-level data from FLUXNET, and other recently available datasets. Subsequently, I will focus on the impacts of vegetation energy, water and carbon fluxes on the simulated permafrost and the carbon stored therein. The overarching goal of this talk will be to quantify the uncertainties from key model parameterizations vs. those from input meteorological and land-cover datasets. The aim of the uncertainty analysis will be to highlight the relative importance of continued model development efforts vs. the required improvement in the datasets.