New Zealand surrounded by Biggest Waves on the Planet

New Zealand is bang in the middle of the biggest and wildest waters on the planet: the Southern Ocean.

Many of New Zealand’s coasts and coastal communities are already facing the impact of rising sea levels. Will the future see even bigger storms and waves, putting our increasingly intensive development of coastal areas dramatically at risk?

Faced with this scenario, NIWA scientists are using special modelling techniques to build a long record of wave conditions from which they can predict future wave conditions.

“The height of the waves relates to the danger facing our coastal areas. The most dangerous place is along the south and west coast of the South Island, with Fiordland seeing some of the highest waves. Wave heights average three metres on a typical day, but reach over ten metres at times. Wave heights in the North Island average around two metres on much of the west coast, and one metre on the east coast,” says NIWA scientist Dr Richard Gorman.

The scientists are looking at the existing climate and at how future projections of climate change could affect wave height. This NIWA research programme will develop and produce regional projections of waves, swells and storm surge on a national scale. These projections will support local government, engineering and planning consultants in making decisions about adapting to climate change in coastal areas.

“If you want to know about climate you need a long record to base it on. Unlike the data from meteorological stations, some of which have been in place for over 100 years, that length of record is not available for waves where the longest record (from Baring Head near Wellington) is only 15 years. So we use numerical modelling to fill in the gaps in the record,” says Gorman.

Modelling backwards in time to get this wave data is called a ‘hindcast’.

In the first stage of the research, a 45-year long hindcast of wave conditions around New Zealand was created using a numerical model. The model takes wind data from the European Centre for Medium ange Weather Forecasts (ECMWF), one of the main agencies for weather forecasting around the globe, and from this it can simulate waves over the long timescales the scientists need.

The resulting wave statistics have been tested for accuracy and calibrated by comparison with satellite data and with records from a global set of wave buoys.

A similar hindcast has been run for storm surge, in work led by Dr Emily Lane, and tested against measurements from sea-level recorders around New Zealand.

In the next stage of the research, the NIWA scientists will go from using inputs from the European Centre for Medium range Weather Forecasts weather model, to using the results of climate models capable of projecting the effects of different greenhouse gas emission scenarios on winds and sea level pressure.

Climate model inputs will be used to drive wave and storm-surge models simulating the past, so the models can be tested.

Having run all of their checks, the scientists will begin the third stage of the research. Simulations for the period 2070-2100 will be used to investigate projections of future wave and storm surge climates. Projections will be made for different greenhouse gas emission scenarios.

When completed, this information will be available to everyone through a new web-based system. The science will be completed in 2012.

This research is funded by Ministry of Science and Innovation (MSI).

Measurements from sea level recorders around New Zealand are available at http://www.niwa.co.nz/our-services/online-services/sea-levels

ENDS

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