CGRG Bibliography of Canadian Geomorphology
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Author : Frechette, B.; Wolfe, A.P.; Miller, G.H.; Richard, P.J.H.; and de Vernal, A.
Date : 2005.
Title : Vegetation and climate of the last interglacial on eastern Baffin Island, Arctic Canada.
Publication : 35th Annual International Arctic Workshop. March 9-12, 2005. Timms Centre for the Arts, University of Alberta, Edmonton, Alberta, Canada.
Issue :
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Abstract
Sediment cores recovered from three mid-arctic lakes on eastern Baffin Island contain two superimposed sediment packets of weakly stratified lacustrine gyttja, which are separated by stratified minerogenic sediment. Radiocarbon ages on aquatic macrofossils in the lower lacustrine unit are greater than 50 ka, and luminescence ages on two of these cores suggest that the unit belongs to the early part of the last interglacial sensu lato, >90,000 years BP and <130,000 years BP. Pollen spectra from these cores are used to reconstruct past vegetation and climate of Holocene and last interglacial periods. The last interglacial sediment in the three sequences exhibits (1) very high pollen concentrations, (2) shrub-dominated (Betula, Alnus) pollen spectra, with few arctic herbs and long-distance pollen grains, (3) low palynological diversity, interpreted as the result of a local dense shrub tundra vegetation. In comparison, the Holocene spectra exhibit higher palynological diversity, interpreted as the result of a sparse, less productive herb tundra vegetation. From these results, we conclude that a shrub tundra vegetation, with shrub Betula, colonized the Cumberland Peninsula during the last interglacial period. Comparison by correspondence analysis of fossil pollen spectra to a data-set of 400 high-latitude modern lake sediment samples reveals that the vegetation of the last interglacial on east-central Baffin Island was Low Arctic in character and comparable to present-day southwest Greenland. From application of correspondence analysis regression and best modern analogue method, we show that July air temperatures of the last interglacial were 4 to 5°C warmer than present on eastern Baffin Island, which is warmer than any time in the Holocene. At the optimum of the last interglacial, the July air temperatures were high enough to have allowed the establishment of a shrub birch vegetation and small tree birch and alder populations on Cumberland Peninsula. Tree birch may well have been growing in protected lowland areas, but there is no evidence that alder ever grew on Baffin Island, possibly due to the geographic barriers to migration. Regardless, the calculated warmth of the last interglacial implies that the Low Arctic phytogeographical zone on Baffin Island extended several hundred km farther north during the last interglacial period relative to the present day. Our data suggest regionalism in the last interglacial palynostratigraphical and climatostratigraphical signatures. Although our sites have recorded different Holocene vegetation histories, there is consistency in their interglacial shrub tundra representation. Based on the clear evidence of terrestrial summer warmth greater than at any time in the Holocene, we equate the interglacial sediment with the last interglacial sensu stricto, ca. 117 to 130 ka BP (Marine Isotopic Stage 5e).
Bibliography of Canadian Geomorphology