On the projected changes in New Zealand's wave climate and its main drivers

ABSTRACT

Wave climatologies from historical and projected simulations of the ACCESS1.0, MIROC5 and CNRM-CM5 Global Circulation Models (GCM) were sourced from the Coordinated Ocean Wave Climate Project (COWCLIP) and downscaled using the SWAN wave model. Biases between GCM's historical simulations and a regional hindcast were assessed, and the two best-performing models (ACCESS1.0, MIROC5) had their projections analysed. A general increase in wave height and period was observed along the south/west, together with a decrease in $H_s$ along the north/east coasts. The projected near-term (NEA21C) period shows mostly a $H_s$ increase, whilst for the long-term (END21C) period, increased and decreased $H_s$ are present. The areas of statistically significant changes are larger in the END21C than in the NEA21C period. The wave direction change is counter-clockwise along the west and clockwise along the east coasts. This study is a first assessment of historical and projected GCM-forced waves along New Zealand and the database we generated can be of great value for renewable energy research, risk assessment and the mitigation of future coastal hazards.

KEYWORDS:

• CMIP5
• global climate projections
• New Zealand
• wind waves
• multimodal spectra
• wave downscaling
• SWAN

Acknowledgments

All the programming code for this research was written in Python programming language (www.python.org) and all the plots displayed were created with python's matplotlib module (Hunter 2007). Finally, the authors wish to thank all the scientists that have contributed in building the databases used in the present study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The current research is funded by the now defunct GNS-MBIE research programme ‘Climate impacts on weather-related hazards’, through a grant to GC (contract 3710440). FJM acknowledges the Spanish Ministry of Science for the funding of project PID2019-107053RB-I00.