A large wet snow avalanche cycle in West Greenland quantified using remote sensing and in situ observations

Jakob Abermann,Markus Eckerstorfer,Birger Ulf Hansen,Eirik Malnes

doi:10.1007/s11069-019-03655-8

Jakob Abermann, Markus Eckerstorfer + Show 2 more

Open Access

https://doi.org/10.1007/s11069-019-03655-8

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Abstract

On 11 April 2016 we observed high slushflow and wet snow avalanche activity at the environmental monitoring station Kobbefjord in W-Greenland. Snow avalanches released as a result of snow wetting induced by rain-on-snow in combination with a strong rise in air temperature. We exploit high-resolution satellite imagery covering pre- and post-event conditions for avalanche quantification and show that nearly 800 avalanches were triggered during this cycle. The nature of this extraordinary event is put into a longer temporal context by analysing several years of meteorological data and time-lapse imagery. We find that no event of similar size has occurred during the past 10 years of intense environmental monitoring in the study area. Meteorological reanalysis data reveal consistent relevant weather patterns for potential rain-on-snow events in the study area being warm fronts from Southwest with orographic lifting processes that triggered heavy precipitation.

Highlights

Wet snow avalanches are a common type of snow avalanche and can release from a point or as a slab, in both cases transporting high-density snow masses downslope at relatively low flow velocities (McClung and Schaerer 2006)
We know that most avalanches released between April noon and April noon as this is evident from the daily time-lapse images available in the region (Fig. 3)
A relative backscatter difference between avalanche debris and surrounding undisturbed snow of 3.7 dB was previously used (Eckerstorfer and Malnes 2015). They formulated a qualitative model of backscatter from dry and wet snow avalanche debris based on an earlier study (Ulaby et al 1986)

Summary

Introduction

Wet snow avalanches are a common type of snow avalanche (hereafter called avalanche) and can release from a point or as a slab, in both cases transporting high-density snow masses downslope at relatively low flow velocities (McClung and Schaerer 2006). The occurrence of permafrost or a frozen bed underneath the snowpack impedes meltwater infiltration in the soil; slushflows are common in the Arctic (Washburn and Goldthwait 1958; Nobles 1966) Their potential of destroying infrastructure is especially high in more densely populated areas of the Arctic such as Norway (Hestnes 1998), Iceland (Decaulne and Sæmundsson 2006) or Alaska (Onesti 1985). The majority of impact studies deal with impacts of extreme winter weather events on the ecosystems (Bokhorst et al 2009; Hansen et al 2014; Cooper 2014) It is, likely that wet snow avalanche activity will increase in frequency, threatening growing populations and infrastructure as it was pointed out by Eckerstorfer and Christiansen (2011)

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