Grain-size analysis and Arcellinida as tools for inferring paleoclimatological variability: a case study from Holocene Canadian Subarctic Lake Sediments

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Macumber, Andrew Lloyd




The central Northwest Territories of the Canadian Subarctic, and the myriad of lakes found therein, has through previous research been shown to archive records of past Holocene climate variability. Due to the low temporal resolution of previous paleoclimatic reconstructions questions remain as to past rates of natural climate change, a deficiency of concern to policy makers and modelers responsible with addressing human induced climate change. Two paleolimnological proxies of climate variability, end-member mixing analysis (EMMA) of lake grain-size distributions and the Arcellinida were further developed to increase the temporal resolution of paleoclimate reconstructions and provide a more complete picture of environmental response to past climate variability. A mm-interval subsampling strategy made possible through use of a custom-designed sledge microtome combined with EMMA of lake sediment cores significantly increased the temporal resolution of paleoclimate reconstructions. EMMA of lake sediment cores was used to describe changes in lake catchment hydrology and track the rate of climate deterioration and subsequent amelioration associated with known Holocene events such as the Holocene Climate Optimum (HCO) and the onset of the Neoglacial. Arcellinida as demonstrated here, are sensitive to treeline dynamics. Due to their well-preserved dissolution-resistant tests, rapid generation time and trophic position within lacustrine environments they offer unique insight into climate variability and change. Arcellinida are also characterized by ecophenotypes, which respond markedly to changing environmental conditions making them valuable tools for reconstructing environmental change. Three ecological transitions were seen in the observed Arcellinida communities through the past ca. 6600 cal yBP. Zone 1 spanned ca. 6600-2800 cal yBP and characterized the hydroecology of the lake during the HCO. Zone 2 spanned ca. 2800-140 cal yBP, which represents the Neoglacial. Zone 3 spans ca. 140 cal yBP to present and archives the recovery of the region from the Little Ice Age. Further development of these proxies will help to constrain the rate of climate variability and increase our understanding of the many ways in which the environment responds to climate change. This has implications not only for the Canadian Subarctic but for the Taiga biome, the largest terrestrial biome in the world.






Carleton University

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Earth Sciences

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