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, were identified, enumerated, and interpreted quantitatively. The samples span a latitudinal transect from 62 to 74 degreesN, reflecting climatic and vegetational gradients that range from low Arctic to transitional mid-Arctic to high Arctic. While the sampled lakes encompass both predominantly maritime and continental climatic regimes, sites have been deliberately restricted to basins in Precambrian crystalline terrain to mitigate the edaphic consequences 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 temperature as significant environmental controls over diatom assemblages. Using weighted-averaging regression and calibration, predictive models for these parameters have been developed. When applied to down-core assemblages, the summer lake water temperature model provides realistic reconstructions when compared with other paleoenvironmental records. Over the past 5000 years, the amplitude of reconstructed summer lake water temperature is on the order of 4.0 degreesC, expressed primarily as progressive Neoglacial cooling culminating in the Little Ice Age. Diatom-inferred summer water temperatures have increased by 2.0 degreesC in the past 150 years, again in agreement with independent paleoclimatic reconstructions.