Using an expanded surface sample data set, representing lakes distributed across a transect from southernmost
Canada to the Canadian High Arctic, a revised midge-palaeotemperature inference model was developed for
eastern Canada.Modelling trials with weighted averaging (with classical and inverse deshrinking; with and without
tolerance downweighting) and weighted averaging partial least squares (WA-PLS) regression, with and without
square-root transformation of the species data, were used to identify the best model. Comparison of measured
and predicted temperatures revealed that a 2 component WA-PLS model for square-root transformed percentage
species data provided the model with the highest explained variance (r2
jack= 0.88) and the lowest error estimate
(RMSEPjack =2.26 0C).
Comparison of temperature inferences based on the new and old models indicates that the original model may
have seriously under-estimated the magnitude of late-glacial temperature oscillations in Atlantic Canada. The new
inferences suggest that summer surface water temperatures in Splan Pond, New Brunswick were approximately 10
to 12 0C immediately following deglaciation and during theYoungerDryas. During the Allerød and early Holocene,
surface water temperatures of 20 to 24 C were attained. The new model thus provides the basis for more accurate
palaeotemperature reconstructions throughout easternmost Canada
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