Isolating the Impact of human-induced Arctic Sea Ice Loss on the Atmosphere

Abstract:

Changes in Arctic sea ice play an important role in modulating surface fluxes of heat and moisture, and therefore local near-surface temperatures and precipitation. Whether or not historical sea-ice retreat has had a marked influence on remote climatic changes remains an open and important question. Here the effects of historical sea-ice loss on the atmosphere are isolated by prescribing Arctic sea ice loss from two different observational datasets to an atmosphere-only model. In addition, we prescribe to the atmosphere-only model sea ice loss patterns simulated by an ensemble of historical simulations with the corresponding coupled model. These simulations allow for the separation of the climate effects of forced (human-induced) sea ice loss and the climate effects of (random) sea ice changes induced by internal variability. We find that all scenarios exhibit a robust, shallow Arctic warming and a tendency for lower Arctic sea level pressure in Autumn and Winter. However, the pattern and magnitude of circulation change outside the Arctic and at upper levels varies widely across simulations. We suggest that midlatitude changes to observed Arctic sea ice loss are dominated by internal variability in the sea ice loss patterns.