Quantifying seasonal cornice dynamics using a terrestrial laser scanner in Svalbard, Norway

Abstract

Abstract. Snow cornices develop along mountain ridges, edges of plateaus, and marked inflections in topography throughout regions with seasonal and permanent snow cover. Despite the recognized hazard posed by cornices in mountainous locations, limited modern research on cornice dynamics exists and accurately forecasting cornice failure continues to be problematic. Cornice failures and associated cornice fall avalanches comprise a majority of observed avalanche activity and endanger human life and infrastructure annually near Longyearbyen in central Svalbard, Norway. In this work, we monitored the seasonal development of the cornices along the plateaus near Longyearbyen with a terrestrial laser scanner (TLS) during the 2016–2017 and 2017–2018 winter seasons. The spatial resolution at which we acquired snow surface data with TLS enabled us to observe and quantify changes to the cornice systems in detail not previously achieved. We focused primarily on the evolution and failure of the lower cornice surfaces where accessibility has precluded previous research. We measured cornice accretion rates in excess of 10 mm h−1 during several accretion events coinciding with winter storms. We observed five cornice fall avalanche events following periods of cornice accretion and one event following a warm period with midwinter rain. The results of our investigation provide quantitative reinforcement to existing conceptual models of cornice dynamics and illustrate cornice response to specific meteorological events. Our results demonstrate the utility of TLS for monitoring cornice processes and as a viable method for quantitative cornice studies in this and other locations where cornices are of scientific or operational interest.

Combining high spatial resolution snow mapping and meteorological analyses to improve forecasting of destructive avalanches in Longyearbyen, Svalbard

“…Hancock, H., Eckerstorfer, M., Prokop, A., and Hendrikx, J., 2020. Quantifying seasonal cornice dynamics using a terrestrial laser scanner in Svalbard, Norway, Nat. Hazards Earth Syst.…”

“…Wind slabs and ice layers form in the snowpack during these warm, wet winter storms and are often separated by persistent weak layers of faceted grains developing during colder, stable periods . Snow is readily transported by the wind across the region's broad plateau summits and expansive glaciofluvial valleys in the absence of woody vegetation, and large cornices develop annually along the edges of the plateaus Hancock et al, 2020). Avalanche activity in this environment clusters temporally around winter storms, where precipitation and strong winds result in modest snow fall amounts rapidly accumulating in leeward areas .…”

Environmental Conditions for Snow Cornice Formation tested in a Wind Tunnel

“…Its maximum length growth rate is 3.2×10 -4 m s -1 , and the average length growth rate during the stable wind speed is 1.4×10 -4 m s -1 . For comparison, in field observations, the measured accretion rate range is 3.9×10 -6 -4.7×10 -6 m s -1 (Hancock et al, 2020) which is two orders of magnitude smaller than the experimental values. The main reason for the discrepancies between the laboratory and the field results is most likely due to observational differences.…”

“…According to Hancock et al (2020), the appropriate wind speed range of cornice growth in the field is 12-30 m s -1 (in a height of 2.8 m). To compare it with our experiments, the mass concentration in this wind speed range was estimated by the following steps for our experiments:…”

Synoptic control on snow avalanche activity in central Spitsbergen

“…Synoptic avalanches climatologies have been developed for Iceland (Björnsson, 1980), the Norwegian mainland (Fitzharris and Bakkehøi, 1986), western Canada (Fitzharris, 1987), the western United States (Birkeland et al, 2001;Schauer et al, 2020), the Spanish Pyrenees (García et al, 2009), Mt. Shasta in northern California (Hansen and Underwood, 2012), and portions of the northeastern United States (Martin and Germain, 2017). Other works investigating synoptic-scale meteorological controls on regional avalanche activity include analyses of the North Atlantic Oscillation's influence on the avalanche regimes in Iceland (Keylock, 2003) and the Eastern Pyrenees (García-Sellés et al, 2010), as well as the effects of the El Niño-Southern Oscillation on avalanche patterns in western Canada and Chile (McClung, 2013).…”