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Open AccessArticle

Dropstones in Lacustrine Sediments as a Record of Snow Avalanches—A Validation of the Proxy by Combining Satellite Imagery and Varve Chronology at Kenai Lake (South-Central Alaska)

1
Renard Centre of Marine Geology (RCMG), Department of Geology, Ghent University, Krijgslaan, 281 S8 Ghent, Belgium
2
Department of Earth and Atmospheric Science, University of Alberta, Edmonton, AB T6G 2E3, Canada
3
U.S. Geological Survey, Anchorage, 4210 University Drive, Anchorage, AK 99508, USA
4
Centre of X-ray Tomography-PProGRess, Department of Geology, Ghent University, Krijgslaan, 281 S8 Ghent, Belgium
*
Authors to whom correspondence should be addressed.
Quaternary 2019, 2(1), 11; https://doi.org/10.3390/quat2010011
Received: 12 December 2018 / Revised: 19 February 2019 / Accepted: 24 February 2019 / Published: 1 March 2019
(This article belongs to the Special Issue Annually Laminated Lake Sediments)
Snow avalanches cause many fatalities every year and damage local economies worldwide. The present-day climate change affects the snowpack and, thus, the properties and frequency of snow avalanches. Reconstructing snow avalanche records can help us understand past variations in avalanche frequency and their relationship to climate change. Previous avalanche records have primarily been reconstructed using dendrochronology. Here, we investigate the potential of lake sediments to record snow avalanches by studying 27 < 30-cm-long sediment cores from Kenai Lake, south-central Alaska. We use X-ray computed tomography (CT) to image post-1964 varves and to identify dropstones. We use two newly identified cryptotephras to update the existing varve chronology. Satellite imagery is used to understand the redistribution of sediments by ice floes over the lake, which helps to explain why some avalanches are not recorded. Finally, we compare the dropstone record with climate data to show that snow avalanche activity is related to high amounts of snowfall in periods of relatively warm or variable temperature conditions. We show, for the first time, a direct link between historical snow avalanches and dropstones preserved in lake sediments. Although the lacustrine varve record does not allow for the development of a complete annual reconstruction of the snow avalanche history in the Kenai Lake valley, our results suggest that it can be used for long-term decadal reconstructions of the snow-avalanche history, ideally in combination with similar records from lakes elsewhere in the region. View Full-Text
Keywords: dropstones; snow avalanche; X-ray CT; varve dropstones; snow avalanche; X-ray CT; varve
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Thys, S.; Van Daele, M.; Praet, N.; Jensen, B.J.; Van Dyck, T.; Haeussler, P.J.; Vandekerkhove, E.; Cnudde, V.; De Batist, M. Dropstones in Lacustrine Sediments as a Record of Snow Avalanches—A Validation of the Proxy by Combining Satellite Imagery and Varve Chronology at Kenai Lake (South-Central Alaska). Quaternary 2019, 2, 11.

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