A comprehensive global study has shown that oceanic wind speeds and wave heights have increased significantly in the last two decades.
Researchers from the Australian National University (ANU) and Swinburne University have used recently developed satellite data to investigate wind and wave trends on a global scale for the first time.
Previously, researchers had to rely on visual observations, point measurements or numerical modeling. These limitations meant they were only able to examine changes to wind speed and wave height on a regional basis.
The researchers analyzed satellite data from 1985 to 2008 and found there was a general trend of increasing wind speeds and wave heights over the period and also a dramatic rate of increase for extreme events. According to the research, over the last 20 years, extreme wind speeds have increased over most of the globe by approximately 10 per cent and extreme wave heights have increased by an average of seven per cent.
ANU Vice-Chancellor, Professor Ian Young, was a part of the research team and said in a media release, “Off the southern coast of Australia, the highest one per cent of waves have increased in height from approximately five meters to almost six meters over the last 20 years.” He added, "Extreme conditions are where we are seeing the largest increases, but mean conditions are also going up."
The researchers say that global changes of oceanic wind speed and wave height are important environmental indicators for climate change.
“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.”
According to a New Scientist article, the researchers don't really know why there has been an increase in wind speed and wave height. There is some speculation that warming oceans and the variability of weather systems may be contributing factors, but in the end Professor Young says, "we don't know the driving force."
What ever the reason, Professor Young suggests that strengthening winds and rising waves could mean more intense storms, hurricanes and cyclones in the near future. He says, ocean winds and waves have a "profound effect on the transfer of energy (heat) between the sea and the atmosphere" and that this is one of the "great unknowns of climate change."
The research results are also expected to have an impact on the design of coastal buildings and structures as well as shipping.
The study was funded under an Australian Research Council Linkage Grant, with sponsorship from MetOcean Engineers and has recently been published in Science.