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Eurasian Ice Sheet and Climate Interactions

Alternative title: null

Awarded: NOK 11.9 mill.

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Project Period:

2014 - 2019

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The overall aim of the project is to reconstruct the Eurasian Ice Sheet during the last Ice Age aiming at a better understanding of the climatic and other factors that have determined the course of the development. Our approach has been to combine empirical data (geological observations) with numerical climate and ice sheet models. We have established a database with published dates from the part of Eurasia that was glaciated. The database (DATED) includes 7671 dates from 3722 locations, compiled from 1189 scientific articles. The data are utilized to create new map-reconstructions of the Eurasian Ice Sheet during the last glaciation. The ice sheet complex attained its maximum extent 20,000 yrs ago, but the eastern margin of the Scandinavian Ice Sheet reached its maximum position 6000 yrs later than in the west. Field based research in Norway have given us new knowledge about the regional changes of the ice sheet configuration, and processes that have been decisive for the course of deglaciation. The islands Utsira and Karmøy became ice free as early as 18,000 yrs ago, probably in response to the collapse of a large ice stream in the Norwegian Channel. The ice front then halted for a long time just outside the coast. In addition to 14C dates of marine mollusks and terrestrial plant remains we have performed many exposure dates of erratic boulders. This is done by measuring the concentration of the isotope 10Be in quartz minerals from their top surface, a method that give a measure of how long they have been exposed for cosmic radiation and thus also when they were released from the ice. It appears that the highest mountain peaks emerged from the ice 20,000 yrs ago, but it went 10,000 yrs before the last remnants of the ice to the east of the water divide disappeared. 16-17,000 yrs ago the ice front started to retreat inwards Boknafjorden that became the first ice free fjord in Norway. The areas further to the north remained ice-covered for a long time. The next phase with rapid retreat happened as a response to a climatic warming that started 14,700 yrs ago, and shortly afterwards the outermost coast was ice free. At about 12,700 yrs ago Northern Europe was hit by a dramatic cooling that lasted 1,100 yrs, a period called Younger Dryas. The ice sheet then grew and advanced on a broad front until the Holocene warming triggered rapid ice sheet disintegration 11,600 yrs ago. By studying sediment cores from lake basins that periodically have been inundated by the sea we have reconstructed the sea-level changes on the islands Karmøy and Bokn where the uplift after the deglaciation have been slower than the sea-level rise in two periods. This implies that the relative sea-level, i.e. the position of the shoreline, was rising twice. We find that the sea-level changes to a significant degree were affected by changes in the gravity field that can be explained by the changing ice mass. In addition, the more common processes such as crustal movements (isostacy) and ncreasing ocean volume (eustacy) played important roles. Model simulations of the outlet glaciers in Hardangerfjorden and Boknafjorden have provided a new and more detailed picture how the ocean and atmosphere have an influence on the ice sheet. We conclude that heating of the sea, as can be seen around Greenland and in the Antarctic today, may be a triggering effect for a rapid disintegration of fjord glaciers. However, it appears that the atmosphere have played an even more important role than the ocean for the deglaciation. One of our collaborators from the Memorial University in Canada, prof. Lev Tarasov, has developed a large scale 3d model of all ice sheets on Earth. Our results from the DATED-database are incorporated in order ensure a realistic ice sheet simulation. This model is now being used as a basis for describing the boundary conditions in global climate models. Based on data from the Russian Arctic we find that the Polar Urals Mountains during an early stage of the last Ice Age, some 60-70,000 yrs ago, was covered by a complex of ice caps that merged with a large ice sheet over the Barents-Kara Sea. This ice melted away during a mild period 50-60,000 yrs ago. A new generation of mountain glaciers formed 30-25,000 yrs ago, but in contrast to Scandinavia and Svalbard, the central valleys in the Ural Mountains remained ice free up to the present. From studies of sediment cores from lakes in the middle of the mountain range we have reconstructed glacier variations and changes in the climate and vegetation throughout the last 60,000 years. All mountain glaciers melted away 15-16,000 yrs ago when Scandinavia was still covered by ice. During a warm period in early Holocene (11,600-5000 yrs ago) the central mountain valleys in the Polar Urals were forested. This is in line with our climate reconstruction on Svalbard based on mollusks indicating that summer temperatures were as much as 6 degrees higher 10-9,000 yrs ago

Vil her fremheve betydningen av DATED-databasen og rekonstruksjonene av det Eurasiske isdekket. Dette arbeidet har vakt stor interesse i det internasjonale fagmiljøet og fremstår som en «mal» for lignende initiativer i andre regioner. Våre rekonstruksjoner er benyttet i globale is- og klimamodeller som simulerer utviklingshistorien på hele jorda. DATED vil også være et fritt tilgjengelig verktøy for videre forskning omkring isdekkenes utviklingshistorie og deres interaksjon med klima, naturmiljø og havnivå. Prosjektet har også bidratt til å utvikle avanserte numeriske is-modeller. Hvordan avsmeltingen har foregått i våre fjorder anses som gode «modeller» for utviklingen på Grønland og i Antarktis. Forskningsaktivitetene har resultert i et tett samarbeid med arkeologer, biologer, klimaforskere, is-modellører, geologer, geografer og geofysikere. Samarbeidspartnere har fått tilgang til unike data som utnyttes til å studere klima og miljøendringer gjennom lange tidsspenn.

The core aim of the EISCLIM Project is to determine the glacial and climatic dynamics that drove the build up and decay of the Eurasian Ice Sheet complex over the last glacial cycle (115,000 - 10,000 years ago). New empirical time-slice reconstructions of this vast former ice sheet will be generated based on existing geological and chronological evidence complemented with new observations from key areas. Glaciological and climate models will be used to investigate causal connections for the recorded chang es. This project builds upon several years of work by the research team to collate a database of published evidence for the last Eurasian Ice Sheet, which will form the basis for the empirical reconstructions. The database will be improved and updated wit h new information as it becomes available to ensure continued relevance as a research tool for the scientific community. We target our efforts to address specific shortfalls in current knowledge and understanding identified by the collation already achie ved. Specifically, we will examine east-west contrasts in ice sheet build up and retreat timing, and provide essential new datasets to generate robust reconstructions of the geometry and thickness of the ice sheet. Expected outputs include: free downloada ble online database of geochronological evidence, 1000-year time-slice maps and model simulations of ice sheet configuration and palaeoclimate conditions through the last glacial cycle (MIS 5d-2), sea level histories, and ice sheet volume, area, thickness , build up and retreat rate estimates. We have considerable support from the wider geological and ice sheet modelling communities for this work and expect that the resulting outputs will have a significant impact on, and be an ongoing legacy for, future c limate research.

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