The polar amplification asymmetry: Role of antarctic surface height
Institute for Meteorology, Universität Leipzig, Vor dem Hospitaltore 1, 04103 Leipzig, Germany
Received: 21 Dec 2016 – Accepted for review: 26 Dec 2016 – Discussion started: 02 Jan 2017
Abstract. Previous studies have attributed an overall weaker (or slower) polar amplification in Antarctica compared to the Arctic to a weaker antarctic surface albedo feedback and also to more efficient ocean heat uptake in the Southern Ocean in combination with antarctic ozone depletion. Here, the role of the antarctic surface height for meridional heat transport and local radiative feedbacks including the surface albedo feedback was investigated based on CO2 doubling experiments in a low resolution coupled climate model. If Antarctica was assumed to be flat, the north-south asymmetry of the zonal mean top of the atmosphere radiation budget was significantly reduced. Doubling CO2 in a flat Antarctica ("flat AA") model setup led to a stronger increase of southern hemispheric poleward atmospheric and oceanic heat transport compared to the base model setup. Based on partial radiative perturbation (PRP) computations it was shown that local radiative feedbacks and an increase of the CO2 forcing in the deeper atmospheric column also contributed to stronger antarctic warming in the flat AA model setup, and the roles of the individual radiative feedbacks are discussed in some detail. A significant fraction (between 24 and 80 % for three consecutive 25-year time slices starting in year 51 and ending in year 126 after CO2 doubling) of the polar amplification asymmetry was explained by the difference in surface height, but the fraction was subject to transient changes, and might to some extent also depend on model uncertainties.
Salzmann, M.: The polar amplification asymmetry: Role of antarctic surface height, Earth Syst. Dynam. Discuss., doi:10.5194/esd-2016-74, in review, 2017.