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.
Bernard Stamm (Cheminees Poujoulat), fights to for survival in a Force 10 storm in mountainous seas the Bay of Biscay, the day after the start of the VELUX 5 Oceans solo round the world yacht race.
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, who earlier this month became Vice-Chancellor of the Australian National University and Swinburne oceanographers Professor Alex Babanin and Dr Stefan Zieger.
'Winds and waves control the flux of energy from the atmosphere to the ocean,' Professor Young said. '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 per cent every year. For extremely high winds, speed increased by a yearly average of 0.75 per cent.
The global increase in wave height was most significant for extreme waves, with the largest one per cent increasing by an average of 0.5 per cent every year. However in some parts of the ocean, extreme waves increased by up to one per cent per annum.
'For example, today the average height of the top one per cent of waves off south-west Australia’s coastline is around six metres. That’s over one metre higher than in 1985,' Professor Babanin said.
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.
'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.'
The study was funded under an Australian Research Council Linkage Grant, with sponsorship from MetOcean Engineers.
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