Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes (Nunavut, Canada) and reconstruction of summer water temperature

Diatoms from the surface sediments of 61 lakes on Baffin Island, Nunavut, w ere identified, enumerated, and interpreted quantitatively. The samples spa n a latitudinal transect from 62 to 74 degreesN, reflecting climatic and ve getational gradients that range from low Arctic to transitional mid-Arctic to high Arctic. While the sampled lakes encompass both predominantly mariti me and continental climatic regimes, sites have been deliberately restricte d to basins in Precambrian crystalline terrain to mitigate the edaphic cons equences of alkaline sedimentary bedrock. Canonical correspondence analysis , using forward selection and Monte Carlo permutation tests, identified pH, conductivity, summer lake water temperature, and mean annual air temperatu re as significant environmental controls over diatom assemblages. Using wei ghted-averaging regression and calibration, predictive models for these par ameters have been developed. When applied to down-core assemblages, the sum mer lake water temperature model provides realistic reconstructions when co mpared with other paleoenvironmental records. Over the past 5000 years, the amplitude of reconstructed summer lake water temperature is on the order o f 4.0 degreesC, expressed primarily as progressive Neoglacial cooling culmi nating in the Little Ice Age. Diatom-inferred summer water temperatures hav e increased by 2.0 degreesC in the past 150 years, again in agreement with independent paleoclimatic reconstructions.