Using avalanche problems to examine the effect of large-scale atmosphere–ocean oscillations on avalanche hazard in western Canada

Abstract

Abstract. Numerous large-scale atmosphere–ocean oscillations including the El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Pacific North American Teleconnection Pattern (PNA), and the Arctic Oscillation (AO) are known to substantially affect winter weather patterns in western Canada. Several studies have examined the effect of these oscillations on avalanche hazard using long-term avalanche activity records from highway avalanche safety programmes. We present a new approach for gaining additional insight into these relationships that uses avalanche problem information published in public avalanche bulletins during the winters of 2010 to 2019. For each avalanche problem type, we calculate seasonal prevalence values for each forecast area, elevation band, and season, which are then included in a series of beta mixed-effects regression models to explore both the overall and regional effects of the Pacific-centered oscillations (POs; including ENSO, PDO, and PNA) and AO on the nature of avalanche hazard in the study area. We find significant negative effects of PO on the prevalence of storm slab avalanche problems, wind slab avalanche problems, and dry loose avalanche problems, which agree reasonably well with the known impacts of PO on winter weather in western Canada. The analysis also reveals a positive relationship between AO and the prevalence of deep persistent slab avalanche problems, particularly in the Rocky Mountains. In addition, we find several smaller-scale patterns that highlight that the avalanche hazard response to these oscillations varies regionally. Even though our study period is short, our study shows that the forecaster judgement included in avalanche problem assessments can add considerable value for these types of analyses. Since the predictability of the most important atmosphere–ocean oscillations is continuously improving, a better understanding of their effect on avalanche hazard can contribute to the development of informative seasonal avalanche forecasts in a relatively simple way.

Upslope migration of snow avalanches in a warming climate

“…Also, the overall patterns and changes may be more nuanced locally, depending on topography (altitudinal range, but also terrain that controls avalanche trigger and propagation). This means that a reduction of avalanche hazards 1) may potentially be enhanced in contexts where snow conditions become affected strongly and homogeneously by global warming, like in the Vosges Mountains, or 2) tempered where large elevation ranges may induce additional complexity [transient regime enhanced by the currently documented trend toward more intense snowfall at high elevations ( 22 ) or by possible specific responses of different avalanche types to climate change ( 2 , 17 )]. Ascertaining these assumptions will require 1) avalanche records that are even longer than the ones we analyzed in this study, that is, historical records extending from the core of the LIA or even earlier, 2) refined forecasts up to the end of the twenty-first century, and 3) reproducing similar analyses in different mountain environments.…”

“…Likewise, literature is also critically lacking regarding future avalanche activity in a warmer climate—the only study currently available ( 16 ) points to a 20 to 30% reduction in avalanche numbers in the French Alps by the end of the twenty-first century as compared to the reference period 1960 to 1990. Several factors explain this lack of direct evidence: first, homogeneous time series of snow avalanches have remained too short for trend analyses over time scales relevant for the detection of climate change impacts ( 12 , 17 ). Second, interpretations may have suffered from confounding influences of climatic and socioeconomical drivers or biases in the proxy data ( 14 , 17 – 20 ).…”

“…Several factors explain this lack of direct evidence: first, homogeneous time series of snow avalanches have remained too short for trend analyses over time scales relevant for the detection of climate change impacts ( 12 , 17 ). Second, interpretations may have suffered from confounding influences of climatic and socioeconomical drivers or biases in the proxy data ( 14 , 17 – 20 ). Eventually, with warming, a temporary increase in extreme snowfall or wet-snow amounts could emerge at higher elevations ( 2 , 21 , 22 ), which in turn could enhance avalanche activity ( 23 ).…”

Tree‐Ring Derived Avalanche Frequency and Climate Associations in a High‐Latitude, Maritime Climate

“…Avalanches also play an important ecological role by modifying landscape and habitat characteristics (Bebi et al., 2009; Rixen et al., 2007). Climate (e.g., coastal, continental) serves as a background influence on snowpack characteristics that drive long‐term patterns in avalanche activity (Armstrong & Armstrong, 1987; Mock & Birkeland, 2000; Mock et al., 2016) or prevalent avalanche problem type (Haegeli et al., 2021), while weather directly influences snowpack structure and avalanches on daily to seasonal timescales. In addition, variability in synoptic‐scale atmospheric circulation and persistent climate modes (i.e., ocean‐atmosphere teleconnections such as the El Niño Southern Oscillation, ENSO and the Pacific Decadal Oscillation, PDO) can have substantial effects on snowpack processes (Abatzoglou, 2010; McCabe, 1994; McCabe & Dettinger, 2002; Mock, 1996; Pederson et al., 2011a, 2011b, 2013) as well as avalanche frequency and behavior (Birkeland & Mock, 1996; Birkeland et al., 2001; Fitzharris & Bakkehoi, 1986; Fitzharris & Schaerer, 1980; Peitzsch, Pederson, et al., 2021).…”

“…Avalanches also play an important ecological role by modifying landscape and habitat characteristics (Bebi et al, 2009;Rixen et al, 2007). Climate (e.g., coastal, continental) serves as a background influence on snowpack characteristics that drive long-term patterns in avalanche activity (Armstrong & Armstrong, 1987;Mock & Birkeland, 2000;Mock et al, 2016) or prevalent avalanche problem type (Haegeli et al, 2021), while weather directly influences snowpack structure and avalanches on daily to seasonal timescales. In addition, variability in synoptic-scale…”