Modelling and characterization of climate, environment, and human impact during the Holocene and Eemian using an Interactive Physical Downscaling
Doctoral thesis
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Date
2024-06-26Metadata
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- Ecology [26]
Abstract
The study of the past climate is important as it provides valuable information about how the earth’s climate has changed over long timescales and helps scientists to better understand natural climate processes and distinguish them from human-induced changes. The Holocene and Eemian epochs represent critical periods in Earth's climatic history, characterized by distinct climate conditions and significant implications for our understanding of past, present, and future climate dynamics. In this thesis, I employ an interactive physical downscaling to our Earth system model of intermediate complexity (iLOVECLIM) to conduct comprehensive simulations of the Holocene and Eemian climates, to unravel the regional intricacies of these pivotal periods. Utilizing the downscaling approach allows us to increase the resolution of the model from 5.56° to 0.25° latitude-longitude in Europe, enabling a detailed examination of regional climate dynamics, including temperature, precipitation, and vegetation patterns. This thesis includes four papers. Transient simulations using both the standard version of the iLOVECLIM and a version with an interactive physical downscaling were performed for the Eemian and the Holocene epoch, as reported in two separate papers. In addition, we have combined archeological data with our downscaled model to simulate the impact of the 536/540 AD volcanic eruption (the Fimbulwinter) within the Holocene period in Scandinavia. In a final paper, bias correction is applied to the downscaling scheme to correct climate model outputs by performing simulations within (the Mid Holocene, the Last Glacial Maximum, the pre-industrial and the Present day). The comparative analysis of these simulations offers a unique opportunity to assess the impact of varying boundary conditions, such as greenhouse gas concentrations, orbital parameters, and land surface characteristics on regional climate patterns. The results show that the interactive downscaling as expected provides more spatial variability in terms of temperature gradient and precipitation in topographic regions such as the Alps, the Scandes mountains and the Scottish Highlands. The results also agree well with other climate models and captures the magnitude of the temperature and precipitation patterns reconstructed by proxy reconstruction during the Holocene and the Eemian in Europe. For example, the Holocene simulations suggest that the downscaling technique simulates approximately 24% more precipitation than the standard version. The simulation for the Eemian at 127 ka produces a magnitude of temperature (3 – 4 °C) and precipitation of (150 – 300 mm/yr) change in the Northern part of Europe relative to preindustrial which is similar to most reconstructions from proxies. Moreover, our simulations with volcanic eruptions applied in 536 and 540 AD reveal a significant cooling in Scandinavia (ensemble mean -1.1 °C), with a sudden decrease in precipitation and a very sharp decline in growing degree days (GDD0) following the volcanic event. Our results imply that a social shift that was already underway was intensified by this sudden climatic anomaly. In the fourth paper, there was a good agreement between the simulated results and the pollen-based biome reconstruction when bias correction was combined with the downscaling in the mid-Holocene and the pre-industrial. Our results demonstrate that we can simulate paleoclimate and vegetation in better agreement with independent reconstructions when bias correction is applied to simulated climate variables. Our study underscores the significance of downscaling as a valuable tool for unraveling the regional complexities of past climates and their implications for the present and future. The insights gained from this research have the potential to advance our understanding of Earth's climatic evolution, contributing to more robust climate models and enhancing our ability to assess the potential impact of ongoing and future environmental changes on regional climates.
Has parts
Paper 1: Arthur, F., Roche, D.M., Fyfe, R., Quiquet, A., & Renssen, H.: Simulations of the Holocene climate in Europe using an interactive downscaling within the iLOVECLIM model (version 1.1). Climate of the Past, 19(1), (2023), 87–106. https://doi.org/10.5194/cp-19-87-2023.Paper 2: Arthur, F., Zapolska, A., Roche, D.M., Li, H., Renssen, H.: Modelling the climate of the Eemian in Europe using an Interactive Physical Downscaling. Manuscript. Not available online
Paper 3: Arthur, F., Hatlestad, K., Lindholm, K.J., Loftsgarden, K., Löwenborg, D., Solheim, S., Roche, D.M., & Renssen, H.: The impact of volcanism on Scandinavian climate and human societies during the Holocene: Insights into the Fimbulwinter eruptions (536/540 AD). The Holocene, 34(5), 2024, 619-633. https://doi.org/10.1177/09596836231225718
Paper 4: Zapolska, A., Vrac, M., Quiquet, A., Extier, T., Arthur, F., Renssen, H., & Roche, D.M.: Improving biome and climate modelling for a set of past climate conditions: evaluating bias correction using the CDF-t approach. Environmental Research: Climate, 2(2), (2023), 025004. https://doi.org/10.1088/2752-5295/accbe2