Late glacial and Holocene vegetation and climate history from easternmost Beringia (northern Yukon Territory, Canada).
During the late Wisconsin glacial episode (28–10 cal ka BP), the Bering land bridge connected the unglaciated parts of Alaska and the Yukon Territory with eastern Siberia to form an extensive continuous landmass known as Beringia. Beringian environments are of particular interest, because they serve...
| Main Authors: | , , , , , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2012
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/31782/ https://hdl.handle.net/10013/epic.40635 |
| Summary: | During the late Wisconsin glacial episode (28–10 cal ka BP), the Bering land bridge connected the unglaciated parts of Alaska and the Yukon Territory with eastern Siberia to form an extensive continuous landmass known as Beringia. Beringian environments are of particular interest, because they served as glacial refugia for various taxa and enabled the migration of plants, animals, and early humans between Eurasia and North America. The northern Yukon Territory was the easternmost boundary of Beringia and in close vicinity to the Laurentide Ice Sheet (LIS). So far, Beringian climate and environmental history are poorly characterized at its easternmost edge. Little is known about vegetation and temperature dynamics northwest of the collapsing LIS close to the Arctic Ocean. Lake sediments from Trout Lake in the northern Yukon Territory have recorded sedimentation, vegetation, summer temperature and precipitation changes since ~16 cal ka BP. Pollen spectra and quantitative climate reconstructions (transfer functions: MAT and WAPLS) indicate that herb-dominated tundra persisted until ~14.7 cal ka BP with mean July air temperatures ≤5°C colder and annual precipitation 50 to 120 mm lower than today. Temperatures rapidly increased during the Bølling/Allerød interstadial towards modern conditions, favoring establishment of Betula-Salix shrub tundra. Pollen-inferred temperature reconstructions recorded a pronounced Younger Dryas stadial in east Beringia with a temperature drop of 2.5 to 3.0°C below modern conditions and low net precipitation of 90 to 170 mm but show little evidence of an early Holocene thermal maximum. Sustained low net precipitation and increased evaporation during early Holocene warming suggest a moisture-limited spread of vegetation and an obscured summer temperature maximum. Northern Yukon Holocene moisture availability increased in response to a retreating Laurentide Ice Sheet, postglacial sea level rise, and decreasing summer insolation that in turn led to establishment of Alnus-Betula shrub tundra from ~5 cal ka BP until present, and conversion of a continental climate into a coastal-maritime climate near the Beaufort Sea. |
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