PALEOENVIRONMENTAL CHANGE INFERRED FROM THE DIATOM SEDIMENTARY RECORD AT ALERT, ELLESMERE ISLAND, NUNAVUT

The Canadian High Arctic is recognized as an important reference area for the study of global environmental change. Despite this, little or no historical climate data exist from across this large region. This missing climate information can, however, be inferred through the development of paleolimnological proxy records using bioindicators such as diatoms.

Alert (82º 30’N, 62º 20’ W), the northernmost human settlement on the planet, is situated on the northeastern coast of Ellesmere Island. It is the site of a Canadian military base as well as a weather station of the Meteorological Service of Canada. In an effort to understand the natural limnological conditions of the area and the effects of environmental change on local water bodies, 30 freshwater sites surrounding Alert were sampled in July and August, 2000 for detailed analysis of water chemistry and diatom assemblages.

Self Pond is a small (~0.3 km²), alkaline (pH=8.3) lake located 8 km southeast of Alert (82º 26’N, 32º 01’W). A 16 cm gravity core was extracted from the deepest part of the lake, and analyzed for diatom relative abundances. Changes identified in the diatom record were correlated to lithological changes in the sediment core.

Throughout much of the history of the sediment core, the diatom assemblage was dominated (i.e. > 90% relative abundance) by the small, benthic diatom Fragilaria pinnata Ehrenberg, which is typical of cold arctic lakes with persistent or prolonged ice covers. In the upper 2 cm of sediments, a change from grey inorganic clays to darker organic sediments was accompanied by lower abundances of F. pinnata, and their replacement by a more diverse assemblage containing other Fragilaria species as well as several other genera. In the upper 0.5 cm of the core, a dramatic decline of F. pinnata occurred, replaced largely by Achnanthes kriegeri Krasske.

Similar striking changes in diatom sedimentary records have been observed further south on Ellesmere Island, as well as on Ellef Ringnes Island to the southwest, and in other high arctic regions. These changes are correlated to those found in other proxy indicators around the circumpolar Arctic, and appear to be indicative of a recent warming trend in the region. These data suggest that a similar, recent warming has occurred on northern Ellesmere Island, which resulted in a dramatic change in lake ecology.