Mar Arroyo

The ocean is a significant sink for fossil fuel CO2 emissions, but the uptake of this additional CO2 alters the ocean’s carbonate chemistry. My work examines how the surface ocean carbon cycle has changed over recent decades using a suite of global ocean biogeochemical models. Accurately capturing these historical carbon cycle changes is essential for constraining the future ocean carbon sink.

The ocean plays a major role in Earth’s climate, presently absorbing ~25% of fossil fuel CO2 emissions from the atmosphere each year. However, fossil fuel CO2 uptake by the ocean causes substantial changes in ocean carbon chemistry. These chemical changes influence how much more fossil fuel CO2 the ocean can absorb over time. I use ocean biogeochemical models to examine how the ocean carbon cycle has changed due to rising fossil fuel CO2 and how these changes affect the ocean carbon sink strength. While models are powerful tools, they do not always agree with each other or with observational data in capturing carbon cycle change. My work evaluates the differences in ocean carbon cycle change between models and quantifies the impact of those differences. A key finding is that the different model responses to fossil fuel CO2 perturbations lead to diverging trends in the seasonal carbon cycle change over time. These inconsistencies impact the net annual ocean carbon sink strength and thus ocean carbon budget estimates. Improving historical carbon cycle representations will help constrain future projections of the ocean carbon sink.