| An important source of information about climate change comes from sedimentary deposits from the arctic region. However, there are few lacustrine fossil records from the central mid Arctic region of Canada. A 485 cm sediment core, from a lake unofficially called JR01, Boothia Peninsula, Nunavut, yielded a high-resolution diatom record. Five radiocarbon dates provided the chronology. Three distinct zones are revealed in the relative percent abundance and diatom concentration diagrams. A more diverse and productive flora in the first zone implies warmer temperatures in the middle Holocene. A complete shift in diatom composition to a predominantly Fragilaria flora and a reduction in diversity and production suggests a cooler climate in this region after approximately 4360 years B.P. Smaller-scale climatic trends, such as the Little Ice Age (LIA) (ca. 550–150 yr. B.P.) and the Medieval Warm Period (ca. 1000–700 yr. B.P.), caused shifts in the diatom flora and production. Subtle shifts in floristic diversity within the LIA may reflect climate variability at a decadal scale. This variability is also recorded in other high-resolution paleoclimate records from the Arctic. A gradual shift to a more diverse and productive flora in the last 180 years B.P. (1790 years A.D.) suggests a response to the recent warming trend. This study permits us to address ambiguities with respect to the timing, the geographic extent and the severity of the recent warming. Changes in total diatom concentrations, magnetic susceptibility, organic and carbonate content may also reflect changes in the diatom assemblages and indicate shifts in vegetation, soil erosion, or in hydrology from the surrounding catchment. The morphological variance of Fragilaria and other taxonomy issues are also discussed. |
