Simulating the extent and depth of spring snow cover for medieval settlements in Iceland and Greenland

Medieval settlements in Iceland and Greenland were vulnerable to changes in spring (April-June) snow cover duration and depth. These would have adversely affected the viability of their pastoral farming systems, but the impact would have been spatially variable. We use a physical-based model of snow distribution and melt to model spring snow cover and depth at a scale relevant to human activities across four sites: southern and northern Iceland, and inner and middle fjord sites in South Greenland, using both present day and simulated climate data from the HadCM3 GCM-model. Our climate scenarios cover the period CE 1000–1500, encompassing a climate shift to cooler conditions. We find that under average present climate conditions the inner fjord site in Greenland has similar spring snow conditions to sites in Iceland, but that the middle fjord site has notably greater snow cover, and as climate cools spring snow cover at this site becomes extensive (>60 days). The largest increase in snow cover duration between current average climate conditions and the coolest climate scenarios (47 days increase) is experienced at our Iceland sites. Inner and middle fjord sites in Greenland diverge in terms of snow cover under all scenarios, a potential driver of the growing importance of marine wild resources and the end of the Norse Greenland settlement.