Introduction Archaeological deposits in Arctic areas are known to hold extraordinary well-preserved organic archaeological remains, primarily due to the cold temperatures and, in some cases, lack of water or oxygen within the depositional environments. The ability to use these organic remains for aDNA (ancient DNA) studies, stable isotope analysis, and trace element analysis attracts front-line researchers from all over the world. Yet, just as new methods increase our ability to retrieve and study this information, climate change poses a dire threat to the continued preservation of the organic data. In recent years, we have studied how climate change may affect organic archaeological deposits in Greenland. Laboratory experiments show that decay rates increase 10-20% for each one degree of warming and furthermore, the optimal condition for microbial activity is at water contents from 40-80% of saturation. The decay of the organic and nutrient rich archaeological material produces great amounts of heat, which may act as an important positive-feedback mechanism that further increases soil temperatures and the speed at which organic materials are lost. For some sites, the combined effects of increasing temperatures, soil drainage, and microbial heat production could lead to a rapid loss of evidence of early human history in the Arctic. It is therefore urgent to act now and develop methods to pinpoint the areas most vulnerable to climate change in order to decide which sites should be excavated now and which sites can be saved for future generations. A single human hair found in a Greenlandic kitchen midden has provided new insight into the first Greenlanders genome. Thanks to permafrost, the hair was preserved for more than 4000 years. However, even in areas without permafrost in the southern parts of Greenland exceptional findings of well-preserved objects of wood, bone, fur, leather, and textile have been made (figure 1). The objects are safe and secure in the cold, damp, and oxygen-poor deposits. At least for a while. Climate change is detrimentally affecting preservation conditions. Over the next century, temperatures in the Greenland and other parts of the Arctic are predicted to rise by as much as 7 degrees Celsius. The hitherto well-preserved archaeological deposits may thereby be exposed to accelerated breakdown and once destroyed, these resources are gone forever with irrevocable impact on cultural heritage and archives of scientific data. Figure 1: Archaeological deposits in Greenland contain extraordinary well-preserved organic remains. From the left: Knives with preserved wooden handles (Qajaa, Saqqaq culture), carved figures of bone (Thule, Dorset culture), preserved textiles (Ikigaat, Norse settlers), and human remains (Qilakitsoq, Thule culture). Photo 1, 2 & 3: Grønlands Nationalmuseum og Arkiv. Photo 4: Nunatta Katersugaasivia Allagaateqarfialu. More than 6000 archaeological sites are currently registered in the Greenland Heritage Database, and only very few have been excavated. The potential of archaeological sites in Greenland to provide further spectacular finds, and thus novel contributions to the understanding Greenland’s and Arctic history, is therefore considered to be very high. Background and Relevance Since 2009 the National Museums of Denmark and Greenland and the University of Copenhagen have collaborated in order to investigate how climate change affects the preservation of organic archaeological deposits in Greenland. As part of this work the project ”Preserving the cultural heritage of Greenland in a changing climate” was initiated in 2013 based on a grant from the Carlsberg Foundation. In this project we set out to study how changes in soil temperature and water content influence the decay of archaeological deposits based on samples from several ancient kitchen middens located along two climatic gradients in Greenland (figure 2). Figure 2: Samples were collected from several sites in south-western Greenland. One of the sites was the kitchen midden at Qajaa in the Disco Bay area where more than 4000 years of history have been preserved in the permafrost. In 2009 a permafrost core was extracted from the site, after which monitoring equipment was installed at various depths. The equipment was connected to a weather station with a data logger (right picture). Photos: Jørgen Hollesen og Jesper Stub Johnsen. Figure 3: As part of the project, the heat production from the microbial metabolism was studied and the results showed that a tipping point can be reached, where the continued degradation of the kitchen midden at Qajaa will be more controlled by the internal heat production than by ongoing climate change. The results were published in Nature Climate Change with a picture of the Qajaa midden on the front page. Research Highlights The results have shown that different types of organic archaeological materials from different parts of Greenland are highly degradable and vulnerable to changes in the soil temperature and water content. The decay rate increases 10-20% for each one degree of warming and furthermore the optimal condition for microbial activity is at water contents from 40-80% of saturation. Consequently, it is very important that the archaeological deposits are kept at cold and at either very wet or very dry conditions. The decay of the organic and nutrient rich archaeological material produces great amounts of heat. We quantified the variability of heat production in different types of organic permafrost soils across Greenland (including a kitchen midden) and documented that the organic material produces enough heat to increase soil temperatures and accelerate the decay processes (Figure 3). Thereby, the impact of climate change on organic soils is enhanced compared to other soil types with crucial implications not only for organic archaeological artefacts, but also for the amounts of carbon being decomposed and potentially emitted to the atmosphere. The rate of degradation was investigated based on measurements of O2 consumption, CO2 production, and heat production at different temperatures and water contents. This is the first time that these three methods have been used in combination to study archaeological materials and hence the results of the project also provide a unique methodological insight that may be useful whenever assessing the vulnerability of organic archaeological deposits. Future Research Microbial decay is not the only threat to Archaeological sites in Greenland. Warmer winters and increasingly favourable growing season conditions lead to more and denser vegetation with deeper roots that causes physical damage to buried artefacts and destroys the integrity of stratified layers. Increasing sea level and storm surge impacts increase coastal erosion rates and represent a great threat for the many archaeological sites located close to the sea. The results of this project, financed by the Carlsberg Foundation, emphasise that it is urgent to act now and develop methods to document and manage the archaeological remains in Greenland. Building on the results, we will begin a new research project in March 2016 entitled ‘REMAINS of Greenland’. Here we will investigate and quantify the short and long-term net effects of different climate-change-induced threats to archaeological sites and artefacts in Greenland. The overall aim is to develop research management tools that can assist the Greenland National Museum to pinpoint the sites most vulnerable to climate change and thereby help them to prioritise and optimise future archaeological investigations. In this manner, the results of our research may help to safeguard our common heritage and be of value not only to the scientific community but also to the society in general. “We cannot prevent climate change, but we can try to limit the damage as much as possible by developing predictive models that show which areas are most vulnerable to the climate threat!” says Senior Researcher Jørgen Hollesen. The impact of climate change on cultural heritage sites is not only a problem in Greenland. In May 2014, the National Museums of Denmark and Greenland hosted the ICOMOS International Polar Heritage Committee Conference - The future of Polar Heritage (IPHC, 2014). One of the issues addressed at the conference was that cultural heritage sites are degrading all over the Polar Regions due to climate changes and that very little has currently been done to address this fact. How the Project Has Affected My Career “The project supported by the Carlsberg Foundation has been of great importance to my career. I am now in a permanent position as Senior Researcher at the National Museum of Denmark and will be PI on the REMAINS of Greenland project, described above. In addition, I have become an expert member of the ICOMOS International Polar Heritage Committee and I am part of the initial organising team for IHOPE Global Environmental Change Threats to Heritage and Long Term Observing Networks of the Past,” says Jørgen Hollesen. More Information Peer Reviewed Articles Related to the Project Hollesen, J., Matthiesen, H., Møller, A.B., and Elberling, B., (2015). Permafrost thawing in organic Arctic soils accelerated by ground heat production. Nature Climate Change 5, 574-578. Matthiesen, H., Jensen, J. B., Gregory, D. Hollesen, J., and Elberling, B. (2014a). Degradation of archaeological wood under freezing and thawing conditions – effects of permafrost and climate change. Archaeometry 56, 3, 479–495. Hollesen, J., Bickersteth, J., Watson, N., Friesen, M., (2014). Conference Review - The 2014 ICOMOS International Polar Heritage Committee Conference - The Future of Polar Heritage, Environmental Challenges in the Face of Climate Change. Conservation and Management of Archaeological Sites 16(3), 283-288. DOI:10.1179/1350503315Z.00000000087 Peer Reviewed Articles Related to the Subject Hollesen, J., Jensen, J. B., Matthiesen, H., Elberling, B., Lange, H., and Meldgaard, M. (2012). Kitchen middens and climate change - the preservation of permafrozen sites in a warm future. In D. Gregory, and H. Matthiesen (eds.) Proceedings from the 4th conference on Preserving Archaeological Remains In Situ. Conservation and Management of Archaeological sites vol. 14, nr. 1-4, s. 159-168 Elberling, B., Matthiesen, H., Jorgensen, C.J., Hansen, B.U., Gronnow, B., Meldgaard, M., Andreasen, C., Khan, S.A. (2011) Paleo-Eskimo kitchen midden preservation in permafrost under future climate conditions at Qajaa, West Greenland, Journal of Archaeological Science 38, 1331-1339. Rasmussen M, Li YR, Lindgreen S et al. (2010) Ancient human genome sequence of an extinct Palaeo-Eskimo. Nature, 463, 757-762.