A 2000 year midge-based paleotemperature reconstruction from the Canadian 2 Arctic archipelago

porinchu, d.f., macdonald, g.m., and rolland, n.

Abstract

Study Location

Lake V57 is a small (9 ha), relatively deep (6.90 m), weakly alkaline (pH = 8.20) lake located in southeastern Victoria Island (69° 39.408 N, 105° 21.436 W). The southeast quadrant of Victoria Island is characterized by a low arctic climate (Environment Canada 2008a). The nearest meteorological station to the study site is located in Cambridge Bay, NU (69.1°N, 105.13°W, 27 m asl). Mean annual temperature at Cambridge Bay for the period 1971-2000 is -14.4°C, with mean July temperature of 8.4°C, and mean winter temperature (DJF) of -28.5°C. Mean annual precipitation varies between 100 and 200 mm for the region.

Climate Proxy

A midge-based inference model for average July air temperature (AJAT) and summer surface-water temperature (SSWT) was recently developed for use in the central Canadian Arctic. The AJAT inference model is based on 77 lakes and 50 midge taxa; the SSWT inference model includes 75 lakes and 50 taxa. A two-component WA-PLS model provides the most robust performance statistics for AJAT, with an r²jack = 0.77, RMSEP = 1.0°C, maximum bias of 1.4°C.

Results

The most striking features of the LOI and chironomid stratigraphies at Lake V57 are an increase in lake productivity, as estimated by LOI, and a trend towards a more thermophilous community after 1600 AD. The shift to a more thermophilous midge community post-1600 AD is characterized by increases in Corynocera ambigua type and Psectrocladius sordidellus type, and decreases in cold-water taxa such as Heterotrissocladius and C. oliveri type. The changes in the midge community occur concomitantly with higher midge-inferred AJAT and SSWT. Beginning at ~1600 AD air and water temperature trended up-ward, with a maxima of 9.1°C and 10.8 °C occurring at 1900 AD for AJAT and SSWT, respectively. The average inferred AJAT is 7.8°C and the average inferred SSWT is 10.0°C between 1000 AD and present. The reconstructed temperature range captured by variations in the midge community in Lake V57 was 2.8°C (6.4-9.0°C) and 1.8°C (9.2-11.0°C) for AJAT and SSWT, respectively.

References

• Environment Canada (2008a) A National Ecological Framework for Canada http://www.ec.gc.ca/soer-ree/English/Framework/NarDesc/
• Finkelstein SA, Gaiewski K (2007) A palaeolimnological record of diatomcommunity dynamics and late-Holocene climatic changes from Prescott Island, Nunavut, central Canadian Arctic.Holocene 17: 803-812
• Peros MC, Gajewski K (2008) Holocene climate and vegetation change on Victoria Island, western Canadian Arctic Quat Sci Rev 27: 235-249

Related websites

• Integrated Paleoenvironmental Laboratory