Browsing by Author "Hancock, Holt"

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Combining high spatial resolution snow mapping and meteorological analyses to improve forecasting of destructive avalanches in Longyearbyen, Svalbard
(Elsevier BV, 2018-10) Hancock, Holt; Prokop, Alexander; Eckerstorfer, Markus; Hendrikx, Jordy
Two naturally triggered snow avalanches occurred on 19 December 2015 and 21 February 2017 in the town of Longyearbyen, Svalbard in the Norwegian high-Arctic. These events resulted in two fatalities, numerous injuries, and rendered fourteen residential buildings uninhabitable. Both avalanches occurred on the west-facing slope of the Sukkertoppen Mountain and were preconditioned by similar meteorological conditions. We investigate these two events by combining traditional weather and snowpack analyses with snow distribution data acquired via terrestrial laser scanning (TLS). As limited snow data exists on Svalbard, the TLS-derived snow depth and differential snow depth maps are the primary viable method for the description and analysis of destructive avalanche activity in this location. These TLS-derived surfaces permit detailed assessment of slope-scale snow distribution patterns both prior to and following avalanche activity. We identify strong easterly winds and moderate to heavy snowfall as precursors to destructive avalanche activity on this slope. The results of our investigation help clarify the relationship between winter storm characteristics and avalanche activity in high-Arctic environments and demonstrate the importance of scale-appropriate snow data for avalanche forecasting with increased precision at finer spatial scales. These results have implications for avalanche forecasting in this setting and other data sparse, high-relief Arctic settings where snow distribution patterns are controlled by wind.
Quantifying seasonal cornice dynamics using a terrestrial laser scanner in Svalbard, Norway
(2020-02) Hancock, Holt; Eckerstorfer, Markus; Prokop, Alexander; Hendrikx, Jordy
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.
Synoptic control on snow avalanche activity in central Spitsbergen
(Copernicus GmbH, 2021-08) Hancock, Holt; Hendrikx, Jordy; Eckerstorfer, Markus; Wickström, Siiri
Atmospheric circulation exerts an important control on a region's snow avalanche activity by broadly determining the mountain weather patterns that influence snowpack development and avalanche release. In central Spitsbergen, the largest island in the High Arctic Svalbard archipelago, avalanches are a common natural hazard throughout the winter months. Previous work has identified a unique snow climate reflecting the region's climatically dynamic environmental setting but has not specifically addressed the synoptic-scale control of atmospheric circulation on avalanche activity here. In this work, we investigate atmospheric circulation's control on snow avalanching in the Nordenskiöld Land region of central Spitsbergen by first constructing a four-season (2016/2017–2019/2020) regional avalanche activity record using observations available on a database used by the Norwegian Water Resources and Energy Directorate (NVE). We then analyze the synoptic atmospheric conditions on days with differing avalanche activity situations. Our results show atmospheric circulation conducive to elevated precipitation, wind speeds, and air temperatures near Svalbard are associated with increased avalanche activity in Nordenskiöld Land, but different synoptic signals exist for days characterized by dry, mixed, and wet avalanche activity. Differing upwind conditions help further explain differences in the frequency and nature of avalanche activity resulting from these various atmospheric circulation patterns. We further employ a daily atmospheric circulation calendar to help contextualize our results in the growing body of literature related to climate change in this location. This work helps expand our understanding of snow avalanches in Svalbard to a broader spatial scale and provides a basis for future work investigating the impacts of climate change on avalanche activity in Svalbard and other locations where avalanche regimes are impacted by changing climatic and synoptic conditions.