Understanding the mechanisms driving the ocean’s anthropogenic carbon reservoir under changing emissions

Understanding the mechanisms governing the evolution of the ocean’s anthropogenic carbon reservoir is critical for assessing its role in the global carbon cycle and susceptibility of the ocean carbon sink to climate change. Anthropogenic carbon, primarily from fossil fuel burning, interacts with and alters the natural carbon cycle, increasing the vulnerability of surface waters to natural carbon leaks. To address these dynamics, we quantify the mechanisms affecting oceanic anthropogenic carbon, including ocean circulation, biological production, and carbonate chemistry, using the Max Planck Institute Earth System Model. By disentangling the multi-factors through separating the evolutions of natural carbon—pre-industrial oceanic carbon pools—and anthropogenic carbon, we aim to develop a clearer and more comprehensive understanding of the ocean carbon cycle. Utilizing idealized emissions-driven simulations, we assess the sensitivity of the ocean carbon sink under varying emission pathways, such as increasing and decreasing CO₂ emissions. This mechanistic understanding is crucial to understanding the vulnerability of the ocean carbon sink and monitoring the carbon budget. By linking these insights to the Transient Climate Response to cumulative CO₂ Emissions (TCRE), this study contributes to a framework for evaluating carbon cycle feedback under diverse emission pathways.