Modern Pollen Deposition and Holocene Paleotemperature Reconstructions, Central Northern Canada

Abstract

The relative modern pollen spectra is reported for a transect from the edge of the boreal forest of Keewatin (ca. 60°N), northeastward to the high arctic/polar desert environments of Clyde River, Baffin Island (ca. 71°N). Two hundred and ninety-three surface moss polsters are analyzed from 29 sites. Thirteen modern pollen taxa (Alnus, Betula, Picea, Pinus, Salix, Artemisia, Chenopodiaceae, Caryophyllaceae, Compositae, Gramineae, Cyperaceae, Ericaceae, and Sphagnum) are used, in association with estimates of present temperature and precipitation, to construct transfer function equations from fossil pollen diagrams. Equations are derived using the Imbrie/Kipp (1971) approach and multiplex regression procedures. The resulting equations are all statistically significant with multiple correlation coefficients for summer temperatures of better than 0.9 with standard errors of ± 1.0°C or less.

The transfer functions are used on four published pollen diagrams (Nichols, 1975) to predict July temperatures. The resulting time-series are presented as standardized departures from the mean July T°C at each of the four sites. A generalized reconstruction of the July temperature history of central northern Canada is then made by taking average departures for each of the four sites over the last 6000 yr. This shows (1) temperatures above average between 5500 and 4000 BP; (2) temperatures below average (or average) between 4000 and 3000 BP; (3) temperatures above average between 3000 and 2000 BP; and (4) temperatures below average between 2000 and the last few hundred years. In addition, on the basis of multivariate statistical analysis, we define four geographic pollen assemblage regions. Proceeding from south to north the pollen assemblages are Region I: Betula/Pinus/Picea/Ericaceae; Region II: Betula/Pinus/Ericaceae/ Alnus; Region III: Ericaceae/Salix/Cyperaceae/Pinus; and Region IV: Gramineae/Cyperaceae/Ericaceae/Salix.