Reduced Ocean Carbon Storage in a Changing Climate due to the Ocean Mesoscale
Ivy Frenger1, Carolina O. Dufour1, Gregory F. de Souza2, Jorge L Sarmiento3, Stephen Matthew Griffies4 and Alison R Gray5, (1)Princeton Univ, Princeton, NJ, United States, (2)ETH Zurich, Institute of Geochemistry and Petrology, Zurich, Switzerland, (3)Princeton University, Program in Atmospheric and Oceanic Sciences, Princeton, NJ, United States, (4)Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States, (5)University of Washington, School of Oceanography, Seattle, WA, United States
Abstract:
It is uncertain how the contemporary ocean carbon sink will develop in future. One process contributing to this uncertainty is the ocean mesoscale, which we will address here using three GFDL global climate models differing only in the resolution of their ocean component. The three models, which include an ocean biogeochemical component, were run under preindustrial atmospheric carbon dioxide levels and an idealized climate change scenario. We use this model suite to assess the effect of (i) better resolving the ocean mesoscale (comparison of a simulation with a 0.1º eddying ocean and one with a 0.25º ocean), and to (ii) assess the skill of the eddy parameterization of the coarse resolution model (comparison of 1º versus 0.1º).(i) We find that an improved representation of the ocean mesoscale results in close to 10% reduction in the uptake and storage of carbon by the ocean.(ii) Taking the 0.1º resolution simulation as ground truth, the coarse resolution ocean is too efficient in taking up and storing anthropogenic carbon, indicating that current Earth system models potentially overestimate ocean carbon uptake by 15%.
The relative fraction of the carbon uptake (44%) and storage (35%) accounted for by the Southern Ocean is very similar between the models, suggesting that the prominent contribution of the Southern Ocean to the global anthropogenic carbon sink is not primarily driven by mesoscale oceanic features. Differences between the resolutions result from differences in the volume of well ventilated waters and different efficiencies of ventilating these waters. The mechanisms for these differences are under current investigation.
