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Reconstruction of climate and ecology of Skagit Valley, Washington, from 27.7 to 19.8 ka based on plant and beetle macrofossils

Published online by Cambridge University Press:  27 October 2021

Jon L. Riedel Open the ORCID record for Jon L. Riedel [Opens in a new window] ,
Alice Telka ,
Andy Bunn  and
John J. Clague
Jon L. Riedel*
Affiliation:
Retired, National Park Service, 7280 Ranger Station Road, Marblemount, WA98267, USA
Alice Telka
Affiliation:
Paleotec Services, 1-574 Somerset Street, Ottawa, ON K1R 5K2, Canada
Andy Bunn
Affiliation:
Huxley College of the Environment, Western Washington University, 516 High St, Bellingham, WA 98225, USA
John J. Clague
Affiliation:
Department of Earth Sciences, Simon Fraser University, 8888 University Dr, Burnaby, BC V5A 1S6, Canada
*
*Corresponding author: 1605 24th Place, Anacortes, Washington 98221, USA. E-mail address: riedeljon7@gmail.com
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Abstract

Glacial lake sediments exposed at two sites in Skagit Valley, Washington, encase abundant macrofossils dating from 27.7 to 19.8 cal ka BP. At the last glacial maximum (LGM) most of the valley floor was part of a regionally extensive arid boreal (subalpine) forest that periodically included montane and temperate trees and open boreal species such as dwarf birch, northern spikemoss, and heath. We used the modern distribution and climate of 14 species in 12 macrofossil assemblages and a probability density function approach to reconstruct the LGM climate. Median annual precipitation (MAP) at glacial Lake Concrete (GLC) was ~50% lower than today. In comparison, MAP at glacial Lake Skymo (GLS) was only ~10% lower, which eliminated the steep climate gradient observed today. Median January air temperature at GLC was up to 10.8°C lower than today at 23.5 cal ka BP and 8.7°C lower at GLS at 25.1 cal ka BP. Median July air temperature declines were smaller at GLC (3.4°C–5.0°C) and GLS (4.2°C–6.3°C). Warmer winters (+2°C to +4°C) and increases in MAP (+200 mm) occurred at 27.7, 25.9, 24.4, and 21.2–20.7 cal ka BP. These changes accord with other regional proxies and Dansgaard–Oeschger interstades in the North Atlantic.

Keywords

Last glaciationMacrofossilsPaleoecologyPaleoclimateSkagit ValleyWashingtonNorth Cascades
Type
Research Article
Information
Quaternary Research , Volume 106 , March 2022 , pp. 94 - 112
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Copyright © University of Washington. Published by Cambridge University Press, 2021

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Footnotes

†

Deceased.

References

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