Polar Amplification in Idealized Climates: The Role of Ice, Moisture, and Seasons
Nicole Feldl, Timothy M. Merlis
Abstract
Abstract The drivers of polar amplification are investigated by isolating the role of sea‐ice processes, moist energy transport, and the seasonal cycle of insolation in two models, an energy balance model and an idealized general circulation model. Compared to a simple ice‐albedo feedback (temperature‐dependent surface albedo), the addition of thermodynamic‐ice processes and the seasonal cycle of insolation profoundly affects seasonal polar warming. Climatologically limited‐extent ice in the warm season permits only small increases in absorbed solar radiation, producing weak warming, while thick, cold ice in the cold season enables a large radiatively forced response. Despite this enhanced winter warming, the annual‐mean polar amplification is modestly reduced by thermodynamic‐ice processes. When latent heat transport is disabled, polar amplification is further reduced by a factor of 1.8 across the range of ice representations, suggestive of a nearly additive warming by ice and moist‐transport processes.