The potential impact of climate change on seasonal snow in New Zealand: part II—industry vulnerability and future snowmaking potential

Seasonal snow in New Zealand is likely to be subject to substantial change due to the impacts of climate change. These changes will have wide ranging impacts on the New Zealand's economy through the energy, agricultural and tourism sectors. In this paper, we assess the impact of climate change, at a micro-scale for a selection of ski area locations in New Zealand. Where available, we have used current observations of snow depth to calibrate the snow model output for the current climate. We consider the change in the number of days with snow depths exceeding 0.30?m, ??snow-days??, at each of these locations for the 2030?C2049 (mid-point reference 2040) and 2080?C2099 (mid-point reference 2090) time periods, for the three different emission scenarios (B1, A1B and A1FI). These future scenarios are compared to simulations of current, 1980?C1999 (mid-point reference 1990), number of snow-days at these locations. We consider both an average year in each 20-year period, as well as a ??worst-case?? year. At each ski area, we consider an upper and lower elevation site. Depending on the elevation and location of the specific site, our analysis shows that there will be a reduction in the number of snow-days in nearly all of the future scenarios and time periods. When we consider a worst-case or minimum snow year in the 1990s, the number of snow-days at each site ranges from 0 to 229, while by the 2040s, it ranges from 0 to 187 (B1), 0 to 183 (A1B) and 0 to 176 (A1FI). By the 2090s the number of snow-days ranges from 0 to 155 (B1), 0 to 90 (A1B) and 0 to 74 (A1FI). We also simulate the hourly future climate for the 2040s and 2090s, for the A1FI scenario, to enable calculations of the potential available time for snowmaking in these two future time periods. We use simulated temperatures and humidity to calculate the total potential snowmaking hours in the future climates. For the snowmaking analysis, only a worst-case year in each time period, rather than an average year, was used to assess the snowmaking potential. This was done to ensure consistency with snowmaking design practices. At all sites, for the A1FI emissions scenario and for both future time periods, a reduction in potential snowmaking hours is observed. By the 2040s, there is only 82 to 53?%, and by the 2090s, there is only 59 to 17?% of the snowmaking time as compared to the 1990s in a worst-case year. Despite this reduction in snowmaking opportunity, snowmaking was still possible at all sites examined. Furthermore, the amount of snow which could be made was sufficient to reinstate the number of snow-days to the lesser of either that observed in the 1990s for each site or to exceed 100?days. While our snowmaking analysis has some limitations, such as neglecting calculation of melt in the man-made snow component, this study highlights the importance of considering adaptation options such as snowmaking for a more complete impact assessment.     

A comparative assessment of the potential impact of climate change on the ski industry in New Zealand and Australia

In this paper we assess the impact of climate change, at a micro-scale for a selection of four sites in New Zealand and Australia. These sites are representative of the key destination ski regions. In contrast to previous work, our work will for the first time, allow for a direct comparison between these two countries and enable both an estimate of the absolute impacts at a given site, as well as the relative impacts between the two countries. This direct comparison is possible because we have used exactly the same snow model, the same 3 global climate models (GCMs) and the same techniques to calibrate the model for all locations. We consider the changes in natural snow at these locations for the 2030–2049 and 2080–2099 time periods, for one mid-range emissions scenario (A1B). This future scenario is compared to simulations of current, 1980–1999, snow at these locations. We did not consider the snowmaking or economic components of the ski industry vulnerability, only the modelled changes in the natural snow component. At our New Zealand sites, our model indicates that by the 2040s there will be on average between 90 % and 102 % of the current maximum snow depth (on 31 August) and by the 2090s this will be on average reduced to between 46 % and 74 %. In Australia, our models estimates that by the 2040s there will be on average between 57 % and 78 % of the current maximum snow depth and by the 2090s this will be on average further reduced to between 21 % and 29 %. In terms of days with snowdepths equal to or exceeding a ski industry useable levels of 0.30 m, at our lowest elevation, and most sensitive sites, we observe a change from 125 days (current) to 99–126 (2040s) and 52–110 (2090s) in New Zealand. In Australia, a reduction from 94 to 155 days (current) to 81–114 (2040s) and 0–75 (2090s) is observed. In each case the changes are highly depended on the GCM used to drive the climate change scenario. While the absolute changes will have direct impacts at each location, so too will the relative changes with respect to future potential Australia–New Zealand tourism flows, and beyond. Our study provides an approach by which other regions or countries with climate sensitive tourism enterprises could assess the relative impacts and therefore the potential wider ranging ramifications with respect to destination attractiveness.     

Density fronts in the vicinity of a long ridge

Laboratory experiments concerning the nature of density fronts in a two-layer fluid in the vicinity of a continuous ridge were conducted. The experiments were carried out in a circular rotating test cell containing an annular ridge of uniform cross-section. The density fronts were established by releasing a lighter fluid contained in a bottomless cylinder in the interior of the region defined by the topography into a heavier fluid occupying the rest of the test cell. The system was also equipped with an oscillating plunger located along the test cell axis to produce simulated tidal currents impinging in the normal direction on the ridge; experiments without and with tidal forcing were conducted. The governing parameters for the physical system considered are the Rossby, temporal Rossby, Burger and Ekman numbers and geometrical parameters. It is found that for both the non-forced and tidally forced experiments the fronts were stabilized by the ridge. The fronts in the simulated tidal currents experiments were found to advect radially outward more rapidly at early times than their non-forced counterparts; at large times, the temporal evolution of the front for these forced experiments approached that of the non-forced experiments. In the region interior to the annular ridge, the motion field is highly baroclinic, while outside this region, the flow response at the forcing frequency is barotropic. Scaling arguments regarding frontal position, viscous decay and barotropic oscillatory flow responses are advanced and supported by experimental observations.     

The potential impact of climate change on seasonal snow in New Zealand: part I—an analysis using 12 GCMs

Seasonal snow directly affects New Zealand??s economy through the energy, agriculture and tourism sectors. In New Zealand, little is known about the long-term variability of the snow cover and the expected impacts of climate change on snow cover. The lack of systematic historical snow observations in New Zealand means that information on interannual variability, trends and projections of future seasonal snow must be generated using simulation models. We use a temperature index snow model to calculate the accumulation and ablation of the current (1980?C1999) snowpack for more than 37,000 third-order river basins with 100?m contour intervals, resulting in over 200,000 individual model elements in New Zealand. Using this model, which captures the gross features of snow under the current climate, we assess the range of likely effects of climate change on seasonal snow in New Zealand using downscaled temperature and precipitation changes from the middle of the road (A1B) climate change projections from 12 general circulation models (GCMs). For each of the 12 GCMs, we consider two future time periods 2030?C2049 (mid-point reference 2040) and 2080?C2099 (mid-point reference 2090). These future time periods are compared to simulations of current, 1980?C1999 (mid-point reference 1990), seasonal snow. Our results show that on average at a national scale, at nearly all elevations, the 2040s and 2090s result in a decrease in snow as described by all of our summary statistics: snow duration, percentage of precipitation that is snow and peak snow accumulation in each year. This decrease in snow is more marked at elevations below 1,000?m but is evident at all but the very highest elevations. Relative to snow simulations for average peak snow accumulation for the present, we observe that by the 2040s, depending on the GCM used, there is a reduction of between 3 and 44?% at 1,000?m, and an increase of 8?% through to a reduction of 22?% at 2,000?m. By the 2090s, the average reduction is greater, with a decrease of between 32 and 79?% at 1,000?m and between 6 and 51?% at 2,000?m. More substantial reductions are observed below these elevations. When we consider the elevation where snow duration exceeds 3?months, we see a rise in this elevation from 1,550?m in the 1990s to between 1,550 and 1,750?m by the 2040s and 1,700 and 2,000?m by the 2090s, depending on the GCM used. The results of this work are consistent with our understanding of snow processes in general and with work from other similar mid-latitude locations.