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ASYNCHRONOUS ECOLOGICAL RESPONSES TO CLIMATIC CHANGE IN CANADIAN HIGH ARCTIC LAKES AND PONDS
ANTONIADES, DERMOT University of Toronto.
Douglas, Marianne S.V. University of Toronto.
Smol, John P. Queen's University.
The Canadian High Arctic is recognized as a critical reference area for the detection of global environmental change, as research indicates that it has been disproportionately affected by recent climatic change. Predicted future climate change is also expected to have dramatic effects on lakes and ponds in the Canadian High Arctic. Because there is a paucity of historical climate data from this large region, proxy records developed from paleolimnological techniques are crucial to understanding the climate history of the High Arctic. Studies have been published detailing distinct qualitative changes in diatom sedimentary records over the last ca. 200 years from several high arctic sites. However, almost no studies exist which apply transfer functions to quantify these environmental changes.
Diatom inference models were constructed using samples collected from ninety lakes and ponds from Ellef Ringnes, Ellesmere, and Prince Patrick islands. These sites range in latitude from 76º13' to 82º31' N, and from 61º31' to 119º21' W longitude, and, despite broad similarities in climate regime across this area, the diversity of geological and vegetational characteristics resulted in large limnological gradients (i.e. pH 5.1-8.9, median 7.9, conductivity 10-2130 μS, median 162 μS, TPU 3.4-256.9 μg/L, median 11.6 μg/L). Transfer functions for pH (RMSEP = 0.40, r2boot = 0.77) and conductivity (RMSEP = 0.28, r2boot = 0.70) were developed using this biological and limnological dataset.
An examination of sediment cores from Isachsen, Ellef Ringnes Island, and Alert, Ellesmere Island, revealed marked shifts in the stratigraphic record in both regions. Assemblages with relatively few species dominated the lower portions of all sediment cores examined. These dominant species diminished in importance within the upper several centimetres of the cores, and were replaced by new assemblages with much greater species diversity.
The application of diatom transfer functions to these cores suggested relatively stable pH and conductivity throughout most of the history of these cores, with large inferred increases both variables in the during the last two centuries at Isachsen, but only during the last decade at Alert. The trends in conductivity and pH mirror temperature records from high arctic weather stations, and may reflect higher productivity and evaporation resulting from warmer observed temperatures over the last decade.
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