The oceans around New Zealand are regional warming hotspots where sea surface temperature (SST) is rising much faster than the global average. This has profound ecological, socio-economic and climatic implications, particularly for the Southern Alps, which are highly sensitive to variations in climate. This study uses a sensitivity experiment with a regional atmospheric model to investigate how ocean warming over the past decade (2010–2020) has influenced New Zealand’s climate at different spatial scales, with particular attention to the high-elevation zones of the Southern Alps. The approach addresses the effects of an isolated SST increase, explicitly excluding broader systemic changes associated with global warming.

Results suggest that rising SSTs have driven widespread increases in near-surface air temperature and humidity, particularly in autumn and summer, causing weakened westerlies and altered moisture transport pathways. These larger-scale circulation changes have modified the mesoscale flow regime near the Southern Alps, reshaping precipitation patterns and reducing foehn effects in the eastern lowlands. Crucially, the impacts of the SST increase extend into the alpine environment, where surface warming is amplified and (especially wintertime) snowfall is reduced. Consequently, high-elevation climate regimes have shifted towards warmer and more humid conditions, contributing to greater rainfall dominance and potentially accelerated glacial melt.

This study provides a process-based understanding of the influence of SST changes on both regional and high-altitude climate in New Zealand. The findings emphasize the potential for continued ocean warming to exacerbate high-elevation climate shifts and glacier retreat, with substantial implications for regional hydrology, ecosystems, and human activities.