Researchers are predicting waves will get higher on New Zealand’s west coast, and lower on the east as a result of climate change.
Modelling at the University of Auckland also indicated shifts in wave direction, with implications for coastal erosion as waves hit the shore at altered angles.
Scientists made projections for 2026-45 and 2081-2100 under a high emissions global warming scenario (RCP8.5) and a moderate emissions scenario (RCP4.5).
From 2026 to 2045, the main effect may be a small wave height increase (a maximum of 5%) along the South Island’s west coast, the university said.
READ MORE:
* Building resilience: How to protect Wellington from the rising tide
* ‘A terrifying glimpse of what is to come’: La Niña raises sea levels in the western Pacific by 20cm
* Pounding waves on top of rising sea levels threaten our coastline, but are they actually getting bigger?
KEVIN STENT
Huge swells on Wellington’s South Coast. (file pic)
Through the end of the century, wave heights may increase by 5% to 10% on the west coasts of both islands, with the effect stronger in the south than the north.
Wave heights along the east of both islands may decrease by 5% to 20%, with that range accounting for both emissions scenarios.
Changes were likely to become increasingly evident as the end of the century approached.
Overall, averaging out seasonal variations, surfers and swimmers at Ōhope and Mt Maunganui in Bay of Plenty may encounter waves more than 10% smaller in height by the end of the century, the university said.
Waves could gain in height at Auckland’s Piha and Waikato’s Raglan. At Carters Beach at Westport the maximum projected increase was more than 6%. At Dunedin’s St Kilda, projections ranged from a 0.1% gain to a 13% decline.
Stuff
The remnants of tropical cyclone Dovi whipped up huge swells in Taranaki in February 2022.
The modelling also indicated changes in wave heights could vary depending on the season. So waves could be lower in future than they are now in autumn and summer, and higher in spring and winter.
Coastal oceanographer Dr João Albuquerque started the work in 2016 as part of his PhD thesis. It was led by Professor Giovanni Coco, from Auckland University’s School of Environment.
After more than 4200 supercomputer sessions, results were published on Friday in the New Zealand Journal of Marine and Freshwater Research.
“People might just expect waves to get bigger under climate change, but the picture is a lot more complicated,” Albuquerque said.
The project drew on information from global climate models used by the International Panel for Climate Change, to generate projections of the New Zealand wave climate.
STUFF
Rivers bursting their banks, flash floods and more intense cyclones – how climate change is making floods more extreme.
Winds were the key driver of waves and changes in two atmospheric effects would be key in altering winds around New Zealand and therefore waves, Albuquerque said.
One was the western jet stream – a narrow band of strong wind high in the atmosphere, projected to move south and to intensify. Another was the high-pressure sub-tropical ridge, which is also expected to move south.
Oceans around New Zealand were modelled at a resolution of 10km for the project.
The study was the first to project how New Zealand’s waves could change, and took into account such factors as the frequency and intensity of storms.
The database generated by the project is available free for uses including the risk assessment and mitigation of future coastal hazards such as flooding and erosion, and for studying the potential to generate electricity from waves.
