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)

Sien Thys,Nore Praet,Peter Haeussler,Marc De Batist,Britta Jensen,Maarten Van Daele,Thomas Van Dyck,Elke Vandekerkhove,Veerle Cnudde

doi:10.3390/quat2010011

Sien Thys, Nore Praet + Show 7 more

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https://doi.org/10.3390/quat2010011

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Abstract

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.

Highlights

Over the period 2006 to 2016, an average of 27 people died each year in the United States of America due to snow avalanches [1]
We investigate the potential of lake sediments to record snow avalanches and to reconstruct the avalanche history
We observed snow-avalanche deposits on the five available satellite images over the period 2004 to 2014 along the south shore of the central basin of Kenai Lake (Figures 3 and 4). The majority of these can be found between the Hydroelectric Power Station (HPS) and the Ship Creek Delta (SCD)

Summary

Introduction

Over the period 2006 to 2016, an average of 27 people died each year in the United States of America due to snow avalanches [1]. In the European Alps, the number of fatalities is even higher, with a yearly average of 100 casualties over the past 40 years [2]. Snow avalanches have socio-economic consequences, such as road blockages, and power plant and power line damage [3]. Snow-avalanche records provide insights into possible triggering mechanisms and the periodicity of events. Triggering mechanisms can be both human induced and climate dependent, and understanding these mechanisms helps to assess the hazard. The more accurate and complete the snow avalanche record is, the better snow-avalanche hazards can be estimated and provide important information for infrastructure development [5]

Results

Discussion

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