Numerical Representation of Contemporary Atmospheric Δ; 14; CO; 2; : 2. Three‐Dimensional Simulation and Comparison With Observations
Journal Article
Overview
abstract
Abstract; ; The; 14; C:C ratio in atmospheric CO; 2; (expressed as Δ; 14; C) is a powerful tracer of Earth system carbon cycle processes. In the 21st century, spatio‐temporal variations of atmospheric Δ; 14; C are mainly the result of anthropogenic fossil CO; 2; emissions, but the oceans and terrestrial biosphere also exert significant influence on its variations. Here we present a complete three‐dimensional representation of the impact of; 14; CO; 2; and CO; 2; fluxes on atmospheric CO; 2; and Δ; 14; C for 2000 through 2012. We compare simulated atmospheric Δ; 14; C with approximately 5,000 measurements from both the remote atmosphere and continental areas strongly influenced by fossil CO; 2; emissions. These comparisons demonstrate that the spatio‐temporal characteristics of input surface fluxes developed in Part 1 of this study have high fidelity. Based on good model‐observation agreement, we used the model's ability to determine the relative contributions of fossil, oceanic, and terrestrial fluxes to simulated Δ; 14; C to help explain the origin of the observed variations. During our study period, the pole‐to‐pole difference in atmospheric Δ; 14; C increased, which our analysis indicates results from changes in both fossil and oceanic fluxes. Over the continents, we show that most short‐term variation of Δ; 14; C in the PBL results from atmospheric mixing acting on fossil CO; 2; fluxes. Overall, the validation of our simulations by comparison with observations demonstrates that we understand the processes affecting atmospheric Δ; 14; C at a variety of spatial and temporal scales. This suggests that, especially with an expanded set of measurements, we can use Δ; 14; C to better quantify and understand key carbon cycle processes, especially fossil CO; 2; emissions.;
