From Sea to Summit: Investigating the Explicit Role of SST Increase for Regional and High‐Altitude Climates in New Zealand

• Published in: Journal of geophysical research. Atmospheres Vol. 130; no. 15
• Main Authors: Kropač, E., Mölg, T., Cullen, N. J.
• Format: Journal Article
• Language: English
• Published: 16.08.2025
• Subjects: elevation‐dependent warming; mountain climate; regional atmospheric modeling; sea surface temperature; sensitivity study; Southern Alps
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2025JD043572

The oceans around New Zealand are regional warming hotspots where sea surface temperature (SST) is rising much faster than the global average. 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 highly sensitive alpine regions 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 thermodynamic responses, including increases in near‐surface air temperature and humidity, particularly in autumn and summer. These responses have most likely affected circulation dynamics—such as changes in wind fields and moisture transport—that have modified the mesoscale flow regime near the Southern Alps, reshaping precipitation patterns and reducing foehn effects in the eastern lowlands. The dynamic responses, however, remain subject to uncertainty. Crucially, the impacts of the SST increase extend into the alpine environment, where surface warming is amplified and snowfall is reduced. Consequently, high‐elevation climate regimes have shifted toward 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. Plain Language Summary The oceans around New Zealand are warming much faster than the global average, which impacts the region's climate. Mountain regions like the Southern Alps are particularly sensitive to variations in climate, as even small shifts in temperature and precipitation can have major impacts on glaciers, ecosystems, and water availability. Determining to what extent ocean warming contributes to these local changes is difficult, as it occurs alongside many other global climate changes. This study isolates the effects of ocean warming by using an atmospheric model to simulate New Zealand's climate for 2010–2020 under different sea surface temperature (SST) conditions—one with realistic, observed SSTs and one with modified, colder SSTs reflecting the 1981–2010 average. Comparing the two simulations reveals how rising ocean temperatures alone have influenced the country's climate over the past decade. The results show that ocean warming has made New Zealand's atmosphere warmer and more humid, especially in autumn and summer. This most likely affected wind patterns and atmospheric moisture transport, leading to changes in precipitation across the South Island. In the high elevations of the Southern Alps, many effects are amplified, with a stronger increase in air temperature, less snowfall and a greater dominance of rainfall. Key Points The explicit effect of ocean warming around New Zealand has impacted the region's hydrothermal climate and moisture transport Mesoscale changes include modifications in flow regime, precipitation patterns, foehn effects, and vertical meteorological gradients Changes in high‐elevation climate conditions suggest that ocean warming can strongly impact mountain climates and glaciers