The response of ocean climate change to different heat-flux perturbations over North Atlantic in FAFMIP

Abstract. The diversity of surface flux perturbations, especially for heat-flux perturbations, notably results in uncertainties surrounding the responses of ocean climate change under the global warming scenarios projected by climate/earth system models. However, when imposing heat-flux perturbations on the models, there are strong feedbacks between atmosphere and ocean, causing nearly doubled heat-flux perturbation over North Atlantic (NA). In this study, we quantitatively evaluated the impacts of magnitude changes of heat-flux perturbations over NA on the changes in the Atlantic Meridional Overturning Circulation (AMOC), ocean heat uptake (OHU) and dynamic sea level (DSL) by analyzing eight model responses to the heat flux perturbations experiments in Flux-Anomaly-Forced Model Inter-comparison Project (FAFMIP). We found that the magnitude of the AMOC change was very sensitive to the magnitude change of imposed NA heat-flux perturbation, and the weakening amplitude of the AMOC was nearly halved as the imposed heat-flux perturbation F halved over the NA. The most significant responses of both DSL and OHU to the magnitude changes of NA heat-flux perturbation were mainly found in the Atlantic and Arctic (AA) basin, especially for the NA region. Both the added ocean heat uptake (OHUa) and redistributed ocean heat uptake (OHUr) play roles in OHU changes among the different NA heat-flux perturbation experiments. The magnitude change of NA-mean OHUa was almost linearly related to the imposed NA heat-flux perturbation, while the magnitude change of NA-mean OHUr, which is mainly caused by AMOC change and redistributed heat flux, was not proportional to the imposed NA heat-flux perturbation.