CGRG Bibliography of Canadian Geomorphology
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Author : Frechette, B.; Axford, Y.; Briner, J.P.; and Wolfe, A.P.
Date : 2010.
Title : Arctic biome changes on Baffin Island within the past 200,000 years: lessons from past warm times.
Publication : 7th Annual ArcticNet Scientific Meeting. December 15-17, 2010. The Westin Ottawa, Ottawa,Ontario.
Issue : Programme.
Page(s) : 50-51.
Abstract
A new sediment core recovered from Lake CF8 (70°33’ N, 68°57’ W, 195 m asl) on Baffin Island, Arctic Canada, preserves for the first time the last three interglaciations superimposed between minerogenic sands. Records of insect (Chironomidae) remains, diatoms and biogeochemical parameters are summarized in Axford et al. (2009, Proceedings of the National Academy of Sciences, 106, 18443-18446.). Here we present the pollen record of these three organic units. The vegetation cover of the warm periods of the past 200,000 years will be reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June-July-August- September) will be reconstructed from pollen assemblages using the modern analogue technique. The vegetation and climate results at Lake CF8 will then be compared with other interglacial Baffin Island records. Preliminary results indicate that a succession of Arctic biomes is distinguished from the present interglacial (Holocene, last 10 ka) and the last interglacial sediments (LIG, ca. 130 to 125 ka ago), whereas only one Arctic biome is recorded in the previous interglacial sediments (PIG, ca. 190 ka ago). On northeastern Baffin Island, vegetation cover changes were more important during the LIG than during the Holocene. The LIG vegetation evolved from a prostrate dwarf-shrub tundra to an erect dwarf-shrub tundra and then to a vegetation evolved from a prostrate dwarf-shrub tundra to a hemiprostrate dwarf-shrub tundra. The vegetation at the end of the PIG was a hemiprostrate-prostrate dwarf-shrub tundra. From the pollen record, the LIG was the warmest within the past 200,000 years with July air temperature about 4°C higher than today, and shrub birches were present in the vicinity of Lake CF8. Today, the northernmost shrub birch populations grow about 400 km south of Lake CF8. Experimental summer warming in Arctic regions of Alaska resulted in increased shrubbiness (e.g. Tape et al., 2006, Global Change Biology, 12, 686–702). Increasing shrub abundance during the LIG is an important result as it suggests that the directional changes that occurred on Baffin Island are consistent with experimental tundra warming and recent shrub expansion in Alaska. A shift from herbaceous to woody tundra would have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere, notably through a decrease in albedo. In a global warming scenario, it is important that we improve our understanding of how changes in shrub cover likely influence the behaviour of the climate system.
Bibliography of Canadian Geomorphology