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Holocene climate inferred from biological (Diptera: Chironomidae) analyses in a Southampton Island (Nunavut, Canada) lake

Institut National de la Recherche Scientifique (INRS): Eau, Terre et Environnement (ETE), 490 de la Couronne, Québec, Québec G1K 9A9, Canada; Department of Geography, The Ohio State University, 1036 Derby Hall, 154 North Oval Mall, Columbus OH 43210-1361, USA, rolland.4{at}osu.edu

Isabelle Larocque

Institut National de la Recherche Scientifique (INRS): Eau, Terre et Environnement (ETE), 490 de la Couronne, Québec, Québec G1K 9A9, Canada; NCCR-Climate, Institute of Geography, University of Bern, Erlachstrasse 9A, CH 3013 Bern, Switzerland

Pierre Francus

Institut National de la Recherche Scientifique (INRS): Eau, Terre et Environnement (ETE), 490 de la Couronne, Québec, Québec G1K 9A9, Canada; Centre d'Études Nordiques, Paleolimnology-Paleoecology Laboratory, Université Laval, Québec, Québec G1K 7P4, Canada

Reinhard Pienitz

Centre d'Études Nordiques, Paleolimnology-Paleoecology Laboratory, Université Laval, Québec, Québec G1K 7P4, Canada

Laurence Laperrière

Centre d'Études Nordiques, Paleolimnology-Paleoecology Laboratory, Université Laval, Québec, Québec G1K 7P4, Canada

Concerns about the effects of global warming on Arctic environments have stimulated multidisciplinary research into the history of their long-term climatic and environmental variability to improve future predictions of climate in these remote areas. Here we present the first palaeolimnological study for Southampton Island using analyses of chironomids supported by sedimentological analyses, carried out on a 1 m long core retrieved from a lake located in the northeastern part of the island. This core was made up of marine sediments underneath 65 cm of freshwater lake sediments. A marine shell, humic-acids and chironomid head capsules were used to date this sequence. The Holocene environmental history of the lake consisted of two major contrasting periods. The first one, between about 5570 and 4360 cal. yr BP, was climatically unstable, with common postglacial chironomid taxa such as Corynocera oliveri-type, Paracladius and Microspectra radialis-type. This period also corresponded to the highest chironomid-inferred August air temperature (10°C) for the whole record and to significant increases in major chemical elements as detected by x-ray fluorescence. During the second period, which lasted from about 3570 cal. yr BP until the present, limnological conditions seemed to stabilize after a change to cold oligotrophic chironomid taxa, such as Heterotrissocladius subpilosus-group, with no major variations in the abundance of chemical elements. Inferred August air temperatures ranged between 8 and 9°C. This study provided unique information on the timing of the Holocene Thermal Maximum in the Foxe Basin area, a region with very little information available on long-term climate change. This region showed, so far, relatively few signs of recent climatic change, as opposed to other regions in the High Arctic.

Key Words: Southampton Island • Canadian Arctic • Holocene climate reconstruction • chironomids • x-ray fluorescence • lacustrine—marine transition.

The Holocene, Vol. 18, No. 2, 229-241 (2008)
DOI: 10.1177/0959683607086761


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