The Energetics of a Warming Arctic

The inconsistency between observed and simulated rates of recent Arctic sea-ice decline demands a better understanding of energetics of model simulated Arctic warming. Using various ensembles of perturbed HadCM3 simulations, we investigate the sensitivity of sea-ice decline to ocean heat uptake, air-sea fluxes and atmospheric radiative balance and their changing relationships in a warming climate. In a 22-member ensemble, we find consistent amplification of Arctic surface air temperature changes but much smaller SST changes in both polar regions. This is because the extra solar radiation absorbed by the ocean due to decreasing sea-ice and surface albedo in the summer is mostly lost by increased outgoing long wave radiation in the Autumn with a much reduced air-sea temperature difference. The change in heat loss from the ocean in fall varies widely between the different perturbed physics ensemble members and is shown to be correlated with both the change in the sea-ice area and initial sea-ice area. The change in solar heat flux into the ocean does not show this dependency and varies much less between the perturbed physics ensemble members.