title: Recording high-resolution changes in temperature and hydrology in the Canadian Prairies – proxy development and application
Creators: name: Zwick, Mike Marcell
Publisher: name: University of Glasgow
Year: 2021
Subjects: subject: palaeoclimate, long-chain alkenones, long-chain diols, XRF, ostracod shell geochemistry, compound-specific isotope analysis, CSIA, Canada, Saskatchewan, lake, holocene.

description: The Canadian Prairies rely heavily on ample amounts of freshwater, especially for their agricultural activities. Its position in the rain shadow of the Rocky Mountains and long-distance to major water bodies makes this area prone to re-occurring droughts and occasional floods. Especially the former creates costly natural and socio-economic disasters. Although, our understanding of climate drivers is fairly robust on a global scale, it is incredibly limited on a regional scale, which is indicated by our inability to fully explain the 2000s drought in the Canadian Prairie. Long-term regional droughts have the potential to occur abruptly but there is low confidence in current climate projections of their frequency, severity and timing (IPCC AR5, 2013). This uncertainty is to a large part caused by our limited understanding of climate drivers on regional and sub-centennial spatio-temporal scales. Here, the exceptionally low density of robust, (cross-) validated palaeoclimate records in the Northern Great Plains is particularly problematic. Dendrohydrological reconstructions are sparse, mostly short (&lt;500 years) and of reduced fidelity in this region. Diatom-inferred salinity is based on the premise that water balance (P-ET) in a closed lake is traced by salinity but several in-lake processes exist that can decouple the salinity - water balance relationship. Pollen-inferred temperature/precipitation uses the vegetation's response to climate variability which limits its temporal resolution to 50-100 years. Moreover, training data sets in the Northern Great Plains that are used to find modern analogues are affected by anthropogenic impact on species distribution. The meta-problem for the Canadian Prairies hence is two-fold: we lack a) proxies that allow high spatio-temporal resolution and b) robust, site-validated palaeoclimate reconstructions of multi-millenial length. In this thesis, we substantially contribute to the understanding of the climate system in the Canadian Prairies and how novel proxies in terrestrial palaeoclimatology can offer us valuable insights into past climate variability. We advance comparatively novel proxies (in terrestrial palaeoclimatology) based on long-chain diols, ostracod trace metal geochemistry, X-Ray Fluorescence (XRF) and compound-specific isotope analysis (CSIA). Moreover, we apply long-chain alkenones, CSIA, n-alkanes, pigments, bulk isotope analysis (13C), XRF and grain size analysis to reconstruct past lake surface temperature, hydrology and organic matter composition. In the process, we use cutting-edge technology like Mass Spectrometry Imaging to gain sub-annual insights into temperature variability during the abrupt termination of the Holocene Climatic Optimum. Our ability to understand climate events, their causes and for the recent events (e.g. Dust Bowl Drought) our role in it, can be the cradle of desperately needed changes in how we manage the earth system. Climate reconstructions as the basis for projections offer a glimpse into a potential future and at the same time incentive to avoid that future.