Medieval Icelandic farm abandonment, climate models and volcanic-induced climate change

The Norse settled Iceland from the mid-late 9th century AD, and they established farms across all inhabitable parts of Iceland (Schmid et al. 2017). Many of these farms endured, often through to the present day. Others were not so successful and farm sites were abandoned. It is not clear why some farms continued to be occupied, whilst others nearby did not. As well as socio-economic factors, we know that climate fluctuations must have been crucial, due to the environmentally marginal nature of farming in Iceland. Late springs, the early onset of winter and variations in the time that snow lies on the land can have dramatic impacts on livestock mortality, grazing quality, and fodder production (essential for feeding animals over the winter). Climate change can also drive soil erosion, adding to pressures on farming. Changing patterns of settlement in Iceland is also reflected in the differing fates of Norse colonies in the Faroes and Greenland (Hartmann et al. 2017). High resolution land surface models and meteorological downscaling provide us with an opportunity to better understand the dynamics between landscape, climate and people, and modelling on human/farm scales is key. This will enable neighbouring farms to be compared and the modelling will link directly with archaeological excavations by Icelandic colleagues and others in the North Atlantic Biocultural Organisation (www.nabohome.org).

Global climate models driven with reconstructions of solar variations, volcanic aerosols and land use change can simulate climate variations over past centuries, but only on spatial scales far coarser than the scales on which communities will have experienced climate change impacts. This project will use a high-resolution land surface model and meteorological downscaling to reconstruct impacts on human scales for selected regions in Iceland (Skaftártunga, Hörgárdalur, Mývatnsveit and Svalbard) during the late medieval period (13-15th centuries CE).

Research questions

1) How well can downscaling of climate model outputs reproduce current conditions over northern Iceland and the area to the east of Mýrdalsjökull (Skaftártunga)?
2) Can downscaled climate model outputs recreate past human-scale climatic variations in the selected sites in Iceland?
3) Did volcanic influenced climate fluctuations contribute to farm abandonment in parts of Iceland?

Methodology

Climate reconstructions will be taken from the archive of global simulations in the Paleoclimate Model Intercomparison Project (Jungclaus et al. 2017). Downscaling over landscapes will be achieved with RePLACE, a new model that is being built to implement the capabilities of the PLACE model (Casely and Dugmore 2006) in a flexible physically-based modelling environment for cold regions (Essery 2015).

This modelling work will be closely integrated with archaeologists who have worked on the sites in the areas to be studied. This will require the student to work with the archaeologists and read through archaeological reports from the various relevant sites. This will be crucial to understanding the invaluable environmental evidence provided by archaeological finds. Further details on environmental conditions throughout time will be provided by Sediment Accumulation Rate information found in soil profiles dated by volcanic ash layers (tephrochronology).

Visits to Iceland will help the student to understand the areas being modelled, but also will allow visits to areas that have representative vegetation that is no longer present at the farms being investigated. Seasonal visits may also be required to understand variations in snow cover and its interaction with vegetation types in particular.