Peatlands in Southern South America (SSA), in the path of the Southern Westerly Wind belt (SWW), offer the potential of reliable palaeoclimate archives. This investigation aimed to test the late-Holocene climate signal related to variability of the SWW. Three sites were investigated: San Juan and Karukinka bog, southernmost Chile and San Carlos, a Sphagnum dominated bog, discovered in the Falkland Islands, to form a regional comparison. A multi-proxy approach was used, combining both palaeoecological and stable isotopic methods. At one site, Karukinka, intra-site replicability was tested across three profiles located along a microtopographical gradient. A low number of statistically significant correlations between proxies were evident. KAR-EM-1, the low-hummock profile, displayed the highest number of significant correlations, suggesting an optimal coring location. Chronological uncertainty in the high-hummock profile, KAR-EM-3, was the focus of discussion. Intra-site replicability between the palaeoecological records was improved by plotting the records against a ‘master chronology’, from the mid-hummock profile, KAR-EM-2, assuming a synchronous acrotelm-catotelm boundary across the profiles. The testate amoeba inferred depth to water table (WTD) reconstructions offered the highest intra-site coherence, while the stable isotope records suggested generally poor intra-site replicability. A semi-quantitative method of intra-site comparison was carried out which resulted in a number of climate scenarios. The inter-site comparison assessed correlations between the records from the three sites. A lack of significant correlations between the sites may have been due to regional climate variations and differences in the temporal resolution of the records. Robust climatic inferences were limited to the last 300 years. The WTD reconstructions displayed the highest inter-site coherence and suggested a drying trend after AD 1930 due to a southerly shift of the SWW. Late-Holocene climate variability was inferred from the palaeoecological records from Karukinka. Two periods were identified: a MCA period of generally wetter conditions (AD 750-1100) and a LIA period of overall drier conditions (~AD 1100-1900) during a southerly and northerly shifted SWW respectively, driven by solar variability and polar cell strengthening.

<p> The pollen, charcoal and sediment stratigraphies of two cores from small lakes located northeast of Yellowknife, NWT are examined. The focus of this study is to reconstruct post-glacial vegetation changes in this climatically sensitive area. The resulting vegetation history is compared to similar reconstructions from across Canada. The pollen content of twenty-eight modern sediment samples, collected from the forest, the forest-tundra and the tundra zones were used to aid in the interpretation of the fossil record. Radiocarbon dates indicate that the fossil records from these lakes span ~7 500 years. The initial vegetation, shrub Betula tundra, was established at ~7 000 BP and persisted until ~6 000 BP. The presence of Ericaceae, Myrica, and Sphagnum distinguishes this zone from similar zones from western Canada and suggests the existance of large areas of bog environment. This zone is succeeded by a second shrub tundra zone, which is marked by a dramatic increase in Alnus crispa and Alnus incana. This zone spans from ~6 000 BP until ~5 000 BP. A synchronous increase in Alnus is noted from sites across Canada and is attributed to an increase in moisture. The third zone, spanning from ~5 000 BP to ~3 500 · BP, delimits the existance of forest vegetation defined by the northward expansion of Picea mariana. The delay of Picea mariana expansion into the area relative to its arrival in western Canada can be explained by one of the following: 1) geological differences; or 2) remnant glacial ice retarding climatic amelioration; or 3) the long-wave westerly disturbance, which causes cooler temperatures in the east when warmer temperatures persist in western Canada; or 4) some combination of the above. The decline of forest vegetation at ~3 500 BP marks the establishment of modern tundra vegetation at both sites. Climatic cooling coupled with fire caused the extinction of aboreal vegetation at the study sites.</p> / Thesis / Master of Science (MSc)