Decadal predictions of the oceanic carbon uptake

The world ocean is a major sink of anthropogenic carbon emissions. Besides an overall increase of the oceanic carbon sink in response to fossil fuel carbon emission rise, the oceanic carbon uptake also shows pronounced variability on decadal timescale. To what extent is the decadal variation of oceanic carbon uptake predictable? What are the underlying mechanisms in maintaining the predictability? We address these questions by investigating decadal prediction simulations, in which the Earth System Model is initialized with observations and hence the evolution of the climate and the carbon cycle are well reproduced. 

The strength of the oceanic carbon uptake determines the fraction of carbon remaining in the atmosphere and hence modulates the global climate change.  The oceanic uptake of anthropogenic carbon also perturbs ocean biogeochemical cycles and causes ocean acidification. Therefore, decadal predictions of the oceanic carbon uptake considering both the anthropogenic forcing and the natural variations is crucial for understanding future evolution of the climate change, global carbon cycle, and ocean acidification. 

We explore the predictability of the ocean carbon sink. In the first step the focus was on the North Atlantic CO2 sink. We used decadal prediction systems based on the earth system model of the Max Planck Institute for Meteorology (i.e., MPI-ESM). We found pronounced multi-year variations of the oceanic carbon uptake in the MPI-ESM initialized retrospective predictions. Furthermore, we demonstrated that the potential predictive skill of the oceanic carbon uptake in the North Atlantic western subpolar gyre region is up to 4-7 years. Comparison of the initialized predictions against observations further confirms the predictability of the oceanic carbon cycle. The high predictive skill is mainly maintained in winter, and is attributed to the improvement of the ocean physical state and circulation by initialization. More details on predictions of the North Atlantic carbon uptake can be found in Li et al. (2016).

The variability and predictability of the oceanic carbon uptake show prominent regional features. The goal of our ongoing project funded by MiKlip II is to investigate the decadal predictions of the oceanic carbon uptake and the associated underlying mechanisms.

Contact: Hongmei Li

Project:Opens external link in current window MiKlip II

References:

Li, H., Ilyina, T., Müller, W.A., Sienz, F., Decadal predictions of the North Atlantic CO2 uptake, Nat. Commun. 7:11076, doi: 10.1038/ncomms11076 (2016).