Good for glaciers, bad for people? Archaeologically relevant climate models developed from reconstructions of glacier mass balance

We present a new climate and vegetation model, and discuss applications with a study of medieval land degradation and settlement abandonment in þórsmörk, Iceland. Existing meteorological data are used as the starting point for modelling glacier snowlines (equilibrium lines), and this is developed to model seasonal snowcover, potential vegetation and growing season. The current status and past fluctuations of glaciers across Iceland provide independent spatial and temporal constraints to the model. In þórsmörk, there was extensive landscape degradation and settlement abandonment in the late Medieval period, with an unclear role for climate change. Modelling of the landscape impacts of a 1 °C fall in temperatures shows that climatically induced degradation through reduced vegetation, growing season, and increased snowcover had limited effects on the once settled area, highlighting the importance of anthropogenically driven change. High resolution modelling offers a significant potential for assessing ‘what if’ questions, and identifying key empirical tests.