Climate History along the Arctic Seaboard of Eurasia (CHASE)

The main objective of the CHASE project is to reconstruct climate and environmental changes in the Russian Arctic from the start of the last Ice Age and up to the present day, a period of 120,000 years. This period spans both the build-up and retreat of both large ice sheets covering the Barents and Kara Seas, and smaller glaciers in the Polar Urals. We have also aimed at reconstructing the fauna and vegetation history. This knowledge has provided us with a better understanding of the climate changes experienced in this part of the Arctic, but also similarities and differences with developments in Northwestern Europe, including Norway. It has also been an objective to assess the significance of climate and environmental change for the early human occupation in the Arctic. In the CHASE project we have investigated geological archives from lakes as well as from exposed strata along rivers and coastal cliffs. Our focus is the development in the Polar Urals where we have collected sediment cores and seismic profiles from two deep lakes, Malaya Schuchye and Bolshye Schuchye. These lakes are containing exceptional thick sequences of silt and clay. The project has had a collaborating with a German-Russian lake coring project termed Paleolomnological Transect (PLOT) that is coordinated by one of our partners (prof. Martin Melles) at the University of Cologne, Germany. Dating results from Bolshoye Schuchye, the largest and deepest lakes in the entire mountain chain, indicate that ice free conditions prevailed in the study are throughout the last 60,000 years. This forms a sharp contrast to the development in Scandinavia, the Barents and Kara Seas and Svalbard where large ice caps formed during the last major glaciation that culminated some 20,000 years ago. It seems clear that local glaciers also formed in the Polar Urals during this cold period, but they remained small and did not expand into the lakes. Thus, the sediments in these lakes preserve a continuous record through the peak of the last Ice Age and, and thus provide a rare insight into the long-term climate variability in the Arctic. Studies of the Holocene mollusk fauna around Svalbard show that the summer climate here was as much as 6 degrees warmer than today during the climatic optimum that peaked 10,000-9,000 years ago. The sediment cores from the lakes in the Polar Ural Mountains contain a sequence of annual layers, so-called varves. In combination with many radiocarbon dates (14C) of plant remains found in the sediments this has enabled us to establish a very precise chronology throughout a period that is poorly investigated. The vegetation and fauna history has been explored by using pollen and DNA analysis. So far, more than 160 species of plants have been identified and jointly they reveal some dramatic climatic changes. To our surprise, the DNA analyses have also revealed the presence of several species of earth worms, even during the coldest peak of the last Ice Age. This is also the first time such animals have been recorded in geological records. Furthermore, analysis of organic molecules of plant remains combined with oxygen and hydrogen isotope analysis will provide us with information about the changes in temperature and precipitation. We have also discovered a new paleomagnetic excursion that is dated to the period 20-19,000 years ago. Geo-archaeological investigations based on finds from a Paleolithic site located on the tundra on the western flank of the Polar Urals reveal a rich and varied Ice Age fauna. This also includes bones of a cave lion that lived 14-15,000 years ago, which is one of the youngest known remains of this species. Based on our well dated sediment cores we are now working with detailed studies of the climate change towards the end of the Ice Age, including the cold Younger Dryas cold spell. To our surprise, we found indications that this cold spell in the Polar Urals started 2-3 hundred years earlier than further west in Europe. So far, we have no good explanation for this anomaly, but the cores sheds new light on the development and may contribute to a better understanding of the causal connections. We also find that the Holocene climatic optimum happened as early as 10,000 years ago at which time much of the northern mountain chain was forested. A deforestation occurred 4000 years ago in response to a climatic cooling leading towards the Little Ice Age.

The project has contributed to a better understanding of the role of the Arctic in the global climate system, including driving forces for climate change. This is especially true of the glaciation history and how the climate has affected the growth and decay of glaciers. A particularly surprising finding is that in the Ural Mountains, the glaciers during the Last Glacial Maximum (LGM) were only slightly larger than today while the whole of Scandinavia and Svalbard at this time were covered by gigantic ice sheets. Through DNA, pollen and other fossil analysis we have gained a completely new and more detailed picture of the vegetation and fauna history. Studies of the mollusk fauna from Svalbard and Northern Russia provide new knowledge of the ocean climate during interglacial periods. The results may contribute to refine Ice Sheet, General Circulation Climate and Earth System Models, and thus help to improve the predictive capacity with respect to future changes in the cryosphere.

The overall aim of the CHASE project is to document the climate variability and environmental responses in the Eurasian Arctic, focusing on the past development in the Barents-Kara Sea region and adjacent landmasses. We will address the climatic changes in the Eurasian Arctic throughout the last glacial-interglacial cycle up to the present and assess the impact this variability had on glaciers, landscapes, ecosystems, and early human occupation. The investigations will be a direct follow up of several projects in Northern Russia spearheaded by participants of the research group seated in Bergen. In this proposal we will investigate some unprecedented high-resolution lake records from the Polar Urals together with some other archives in the Russian Arctic. Jointly, these records are spanning some of the most dramatic climatic shifts that have taken place in the Eurasian Arctic over the last 130,000 years. We anticipate that the proposed investigations will provide us with new and important knowledge about the pattern and magnitude of the past climatic changes and their consequences for the ecosystems and landscape evolution. This includes the interaction with ice sheets and alpine glaciers, vegetation cover, run off and the marine environment. In addition to geological and palynological methods we will employ new and novel molecular tools (ancient DNA) and compound-specific isotope analysis (2H,18O) of organic remains that will allow us to reconstruct past floras well as well as the temperature and moisture balance history to a detail that has not been possible earlier. The proposed investigations will be carried out in close collaboration with the newly established German-Russian project termed PLOT (2017-2019) that will undertake a new coring campaign all across the northern margin of the Eurasian continent.