The relative importance of Antarctic sea-ice loss within the response to greenhouse warming

Abstract The response to Antarctic sea-ice loss within a coupled modelling framework is examined in comparison to the response to Arctic sea-ice loss and within the context of general greenhouse warming. Sea-ice loss responses are found to be linear (particularly in response to Antarctic or global sea-ice loss) with respect to the degree of imposed perturbation and additive when perturbations are applied in hemispheres separately and concurrently. Globally, and in the tropical Pacific in particular, Antarctic sea-ice loss plays a relatively larger role than Arctic sea-ice loss in both the atmosphere and the ocean, within the parameters of our experiments. The pattern of response to Antarctic sea-ice loss is also found to more closely resemble that of greenhouse warming, again particularly in the tropics. An extension to multi-parameter pattern scaling is developed to include a scaling factor for Antarctic change in addition to those for tropical warming and Arctic sea-ice loss. The decomposition is applied to the modelled response to Antarctic sea-ice loss to break it down into component partial responses that scale with Antarctic, tropical, and Arctic changes. This reveals the aspects of the response that are directly related to Antarctic change, such as an equatorward intensification of tropical precipitation in the Northern Hemisphere, and those that are modified via the induced changes in the tropics and Arctic, such as Northern Hemisphere temperature change. With this, we hope to gain a deeper understanding of the role of each of these changes for the development of physical mechanisms of the response.