Wind and waves growing across the globe

March 25, 2011
Ocean wave
Oceanic wind speeds and wave heights have increased significantly over the last quarter of a century according to a major new study undertaken by Australian researchers.

The results of the research program - the most comprehensive of its kind ever undertaken - have been published today in the prestigious journal Science.

Studies of climate change typically consider measurements or predictions of temperature over extended periods of time. However this study examined global changes of oceanic wind speed and wave height, which are also important environmental indicators.

It was authored by former Swinburne University Vice-Chancellor Professor Ian Young and Swinburne oceanographers Professor Alex Babanin and Dr Stefan Zieger.

"Winds and waves control the flux of energy from the atmosphere to the ocean," said Young. "So an understanding of whether their parameters are changing on a global scale is very important."

In conducting the study, the researchers analysed satellite data over a 23 year period from 1985 to 2008.

"We found a general global trend of increasing values of wind speed and, to a lesser degree, wave height over this period. The rate of increase for extreme events was most significant."

The data showed that wind speeds over the majority of the world's oceans increased by 0.25 to 0.5 percent every year. For extremely high winds, speed increased by a yearly average of 0.75 percent.

The global increase in wave height was most significant for extreme waves, with the largest one percent increasing by an average of 0.5 percent every year. However in some parts of the ocean, extreme waves increased by up to one percent per annum.

"For example, today the average height of the top one percent of waves off south-west Australia's coastline is around six metres. That's over one metre higher than in 1985," said Babanin.

According to Professor Young it was the researchers' access to satellite data that enabled them to conduct such a comprehensive study.

"Previous attempts to investigate global trends in oceanic wind speed and wave height have relied on visual observations, point measurements or numerical modeling. Due to these limitations, researchers have only been able to examine changes to wind speed and wave height on a regional basis," said Young.

"However our study used recently developed satellite altimeter data sets, which enabled us to investigate trends on a global scale. This has really given us a much clearer picture of what is happening in the world's oceans."