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Millennial study climate change in the Eastern Canadian Arctic using diatom assemblages and oxygen stable isotopes

Diatoms are siliceous organisms composed of amorphous biogenic silica (SiO2 – nH2O). Siliceous organisms are resistant to dissolution and are ubiquitous in lake ecosystems. Diatoms have strong affinities with their habitat, they reproduce rapidly, and the assemblage of species reliably records changes in their environment. Diatoms preserve in the SiO2structure of their frustule (siliceous shell) the isotopic composition of the oxygen present during their formation in lake water. Several studies have successfully reconstructed paleo-temperatures of ocean surface water, hydrological parameters, and changes in the source of air masses, and as a result have confirmed the usefulness of stable oxygen isotopes in diatomaceous silica. Multi-proxy analysis that combines non-isotopic and isotopic indicators is the most promising approach for providing consistent paleo-environmental information. In addition, diatoms can help bridge regional historical gaps where ice cap records are not available. Given the continuing uncertainty about predictions of climate models, future studies in this remote region of the Eastern Canadian Arctic may shed light on postglacial dynamics and evolution. Understanding these postglacial dynamics can reveal important paleo-hydrological connectivity and exchange between terrestrial and marine aquatic ecosystems that have occurred and that may potentially exist in the future with the increased melting of ice caps and ice in the region.

The research project of my postdoctoral fellowship aims to study paleo-environmental changes recorded in arctic lake systems following the last deglaciation. The study site is the Nettilling Fjord area between Nettilling Lake and Cumberland Sound, Nunavut. Several sedimentary sequences, each representing a particular lake in this region, will be analyzed for their physicochemical and biological properties. In order to meet specific objectives (1) the retreat time of glaciers (2) the time of marine invasion and (3) the origin of marine waters in the region, a multi-proxy approach combining the isotopic composition of oxygen and the assembly of sedimentary diatoms will be favoured.