Senior Engineer at the CLIPT Lab - A Stable Isotope Biogeochemistry Laboratory at CEED and Department of Geosciences, University of Oslo, Norway.
Background
2017- Senior Engineer, The CLIPT Stable Isotope Laboratory, CEED and Dept. of Geosciences
Publications
-
Bajard, Manon Julietto Andree; Ballo, Eirik Magnus Gottschalk; Høeg, Helge I.; Bakke, Jostein; Støren, Eivind N.; Loftsgarden, Kjetil; Iversen, Frode; Hagopian, William Martin; Jahren, Anne Hope; Svensen, Henrik Hovland & Krüger, Kirstin (2021). Instability or adaptation of the pre-Viking society to the climate variability of the Late Antiquity?.
Show summary
Understanding how agricultural societies were impacted and adapted to past climate variations is critical to adapt to contemporary climate change and guaranty the food security. However, linking climate and change in the behaviour of a population are difficult to evidence. Here, we studied the climate variations of the period between 200 and 1300 CE and its impact on the pre-Viking and Viking societies in south Norway. We used a retrospective approach combining a multi-proxy analysis of lake sediments, including geochemical and palynological analyses, to reconstruct past changes in temperature and agricultural practices during the period 200-1300 CE. We associated variations in Ca/Ti ratio as a result of change in lake productivity with the temperature. The periods 200-300 and 800-1300 CE were warmer than the period between 300 and 800 CE, which is known as the “Dark Ages Cold Period” in the Northern Hemisphere. During this colder period, phases dominated by grazing activities (280-420 CE, 480-580 CE, 700-780 CE) alternated with phases dominated by the cultivation of cereals and hemp (before 280 CE, 420-480 CE, 580-700 CE, and after 800 CE). The alternation of these phases is synchronous of temperature changes. Cold periods are associated to livestock farming, and warmer periods to crop farming. This result suggests that when temperature no longer allowed crop farming, the food production specialized in animal breeding. The development of activities reached a maximum between 400 and 550 CE and a minimum between 680 and 800 CE, in agreement with archaeological findings. The Viking Age (800-1000 CE) started with an increase in temperature and corresponds to the warmest period between 200 and 1300 CE, allowing a larger development of the agriculture practices and society. Our results prove that the pre-Viking society adapted their agricultural practices to the climate variability of the Late Antiquity and that the Vikings expanded with climate warming.
-
Bostic, Joshua Neilson; Hagopian, William Martin; Svensen, Henrik & Jahren, Anne Hope (2019). Predicting seasonal climate using intra-ring stable isotope analysis.
Show summary
By emitting stratospheric sulphur aerosol clouds that dim the light-energy received from the sun, large-scale volcanic eruptions may cause acute changes in global climate that impact both natural ecosystems and human societies. One example is the 536 Event, a prolonged period of darkness and cooling across the northern hemisphere caused by two separate volcanic eruptions in 536 and 540 CE. Recent mean annual temperature (MAT) and mean annual precipitation (MAP) reconstructions suggest that the decade following the 536 event was one of the coldest and wettest of the past two millennia. This cold period likely contributed to the cultural upheavals that occurred in Scandinavia during the 6th century by reducing the geographic range suitable for cereal grain production. However, while annually-resolved MAT and MAP reconstructions are useful for identifying climatic perturbations, they provide limited insight into the effects of such climate anomalies on regional agricultural productivity due to their limited ability to differentiate summer and winter climatic conditions. To accurately estimate the number of days suitable for growing crops, or Growing Degree Days (GDD), seasonal resolution must be achieved by determining the ratio of summer to winter temperature and precipitation. To reconstruct growing season temperature and precipitation across southern Scandinavia in the decade following the 536 event (535-545 CE), we will combine prior reconstructions of annual mean data with novel analyses of summer/winter temperature and precipitation ratios derived from intra-ring carbon and oxygen stable isotope analysis of Picea abies collected from Raknehaugen, a burial mound in southern Norway constructed in 551 CE. These growing season temperature and precipitation estimates will be combined with other geo-climatic data (latitude, altitude etc.) for regional GDD reconstruction to ultimately determine changes in the geographic range suitable for crop production in Southern Norway following the 536/540 double event. Here, we 1.) Provide a conceptual outline of the project’s expected outcomes and 2.) Demonstrate the ability of intra-ring stable isotope analysis to detect short-term seasonal climatic perturbations in Scandinavia by reconstructing the European summer drought of 1959 from estimates of summer/winter temperature and precipitation ratios derived from stable isotope patterns in Picea abies samples from two locations in southern Norway.
View all works in Cristin
Published Jan. 2, 2017 1:51 PM
- Last modified Apr. 16, 2021 2:37 PM
