Carbon Cycle Dynamics: Sources, Sinks, and Fluxes in Changing Climates

Abstract

The carbon cycle represents one of Earth's fundamental biogeochemical processes, governing the exchange of carbon between the atmosphere, biosphere, hydrosphere, and lithosphere. This paper provides a comprehensive analysis of contemporary carbon cycle dynamics, examining major sources, sinks, and fluxes within the context of anthropogenic climate change. Anthropogenic perturbations have fundamentally altered natural carbon flux patterns, with fossil fuel combustion contributing approximately 9.5 ± 0.5 Gt C yr⁻¹ and land-use changes adding 1.5 ± 0.7 Gt C yr⁻¹ to atmospheric carbon burdens. Ocean and terrestrial ecosystems absorb approximately 2.5 Gt C yr⁻¹ and 3.1 Gt C yr⁻¹ respectively, though sink efficiency shows concerning decline trajectories. Climate feedbacks, including permafrost thaw, ocean acidification, and ecosystem respiration changes, threaten to amplify atmospheric CO₂ accumulation rates. This analysis integrates contemporary observational networks, isotopic constraints, and Earth system models to provide a quantitative understanding of carbon cycle perturbations and their implications for climate stabilisation pathways.