Investigating the Relationship between Last Millennium Climate, Volcanism and Ocean Carbon Using a GFDL Earth System Model

Abstract:

Ocean uptake of CO₂ is driven by a variety of chemical, physical and biological processes and feedbacks. We investigated the impact of volcanic perturbations on air-sea carbon flux and marine carbon variability during the last millennium (851-1850 CE) and historical periods (1851-2010 CE) using a Geophysical Fluid Dynamics Laboratory Earth System Model, GFDL-ESM2G. The model was forced with well-constrained external climate data (solar, volcanic, greenhouse gases, and land use) for the last millennium. Ensembles with various configurations of time-varying climate forcing data were executed, including solar, volcanic, land use, and well-mixed greenhouse gases, while holding all other forcing data constant at 1860 CE values. An all-forcing experiment with all climate forcing data varying in time was also conducted. Prior to 1810 CE, volcanically forced surface atmospheric cooling anomalies correlated with an increase in global ocean carbon uptake for ~10-20 years post eruption, with the tropics (30°S-30°N) showing the largest response and Southern Ocean latitudes showing minimal response. Analysis of the 15 events spanning the LM and HP show snap-shots of the time evolution of marine carbon storage. The 1810 CE and subsequent events show the dominant role of the 30°S to 30°N and the 30°S to 60°S latitudinal bands in marine carbon storage and the transition of the Southern Ocean between 30°S and 60°S from a carbon source to a carbon sink. Our analysis will investigate mechanisms that contribute to variability in the regional uptake of CO₂ during the last millennium and historical periods and the implications for the modern carbon cycle.