Mechanisms for Recent Warming in the Antarctic Peninsula Revealed by Multi-model Analysis

The Antarctic Peninsula has warmed significantly since the 1950s. This pronounced and isolated warming trend is collectively simulated by 29 twentieth-century climate hindcasts done for the Fourth Assessment Report of the Intergovernmental Panel of Climate Change. The qualitative similarity to the observed distribution of Southern Hemisphere temperature change suggests the simulated mechanisms leading to warming in the Peninsula may be relevant to the real world. To understand the factors driving warming trends in the hindcasts, we examine trends in Peninsula region’s atmospheric heat budget in every simulation. Atmospheric latent heat release in Peninsula region increases in nearly all hindcasts, and is generally anthropogenic in origin. These increases are driven by well-documented and well-understood anthropogenic increases in poleward moisture transports as these flows are forced up and over the Peninsula’s steep topography. The latent heat increases can be thought of as the most important cause of simulated anthropogenic warming in the Antarctic Peninsula for two reasons. First, they are typically much larger than the warming effects associated with other types of heat fluxes. And second, their magnitudes, though highly variable across the models, are tightly correlated with the amount of warming in the Peninsula. Thus through an examination of the collective behavior of the model ensemble, we diagnose a mechanism of anthropogenic climate change very difficult to identify with a high degree of confidence through analysis of any one simulation. In this sense, the collective behavior of all the models offers insight into the physics of climate change impossible to obtain from any particular model.