ALBERT

Description: Annual to decadal variations in air–sea fluxes of carbon dioxide (CO2) impact the global carbon cycle and climate system, and previous studies suggest that these variations may be predictable in the near-term. Here, we quantify and understand the sources of near-term (annual to decadal) predictability and predictive skill in air–sea CO2 flux on global and regional scales by analyzing output from a novel set of retrospective decadal forecasts of the Earth system. These initialized forecasts exhibit the potential to predict year-to-year variations in the globally-integrated air–sea CO2 flux up to ~7 years in advance. This initialized predictability exceeds the predictability obtained solely from foreknowledge of variations in external forcing or a simple persistence forecast. The near-term CO2 flux predictability is largely driven by predictability in the surface ocean partial pressure of CO2, which itself is a function of predictability in surface ocean dissolved inorganic carbon and alkalinity. Comparison with an observationally-based product suggests that the initialized forecasts exhibit moderate predictive skill in the tropics and subtropics, but low skill elsewhere. In the subantarctic Southern Ocean and northern North Atlantic, we find long-lasting initialized predictability that beats that derived from uninitialized and persistence forecasts. Our results suggest that year-to-year variations in ocean carbon uptake may be predictable well in advance, and establish a precedent for forecasting air–sea CO2 flux in the near future.