Abstract
Maritime mountain snowpacks exist at near critical temperature thresholds, where small warming triggers disproportionate snow loss. The Craigieburn Range in Aotearoa New Zealand offers an important case study for understanding this vulnerability. Its location, in the lee of the Kā Tiritiri o te Moana | Southern Alps, creates marginal snow conditions that support five ski areas. This study examines past and projected changes in seasonal snowpack dynamics using the Flexible Snow Model (FSM2.0), driven by New Zealand Reanalysis (NZRA) data and validated against ski patrol observations. A 26-year baseline dataset (1992–2018) was used to simulate historical snowpack conditions and was further adapted to represent three Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, and SSP3-7.0) to assess future variability in seasonal snow.
Results demonstrate the extreme sensitivity of this maritime snowpack: mean ski season (July- September) air temperatures at ~1600 m a.s.l. crossed the critical freezing threshold, rising from -1.8°C (1990s) to +0.3°C (2010s), with freezing days declining from 116 to 63 annually. This thermal shift is associated with substantial reductions in snow cover days (-40 days) and snow water equivalent (-58%) over the study period. Under continued warming, average annual snow cover days are predicted to decline from 113 (1995–2014) to 56 (SSP2-4.5) or just 36 days (SSP3-7.0) by 2100. However, under the low-emission scenario (SSP1-2.6), annual snow cover days are projected to stabilise at around 88 days by mid-century. The most severe impacts are projected for lower elevations (1000–1400 m), where SWE could decline by 37–53% by 2040, and up to 95% by the end of the century under high-emission pathways.
These changes have profound implications for ski operations, particularly due to shorter seasons and access challenges linked to rising snowlines. While some near-term decline in seasonal snow appears unavoidable, the growing divergence in emission scenarios after 2040, and the corresponding differences in seasonal snow outcomes, highlights the critical importance of climate mitigation in limiting long-term snow loss and supporting the resilience of snow- dependent industries.