Making waves in global forecasting
- This article featured in Swinburne’s new ‘Research Impact’ magazine, produced in association with Nature Publishing Group.
As climate change causes the Arctic polar ice to retreat more each summer, countries and industry are anticipating the opening of faster and cheaper shipping routes. But the wave and ice conditions that ships will encounter are a big unknown.
Waves are Alexander Babanin’s specialty. The Swinburne Adjunct Professor, and former Director of the Centre for Ocean Engineering, Science and Technology (COEST) is researching the rapidly changing wind and wave dynamics that will affect climate and shipping.
Babanin says this exciting and novel project, funded by the United States Office of Naval Research, involves field research and analysis of data from 20 years of satellite imaging. “The shipping route from South Eastern Asia to Europe via the Arctic is only half the distance of the traditional route via the Indian Ocean and Mediterranean. Imagine how much more economical that is.”
As Arctic ice melts and more of the ocean opens, the waves break up the remaining ice, causing it to melt faster. This in turn creates larger areas of open ocean, bigger waves and, in storms, even more ice broken.
Babanin is recognised as a world expert on wave–air interactions. Research at COEST considers how the waves, winds, currents and ice interact to affect the atmosphere, weather and climate. This metocean research is vital for industry and coastal engineering, he says. It can be applied to design better and safer ships, ports and offshore oil and gas rigs. For example, Babanin says ships that operate in a specific region can save 10 per cent on fuel consumption if they are designed to suit the particular wave conditions.
As well as his studies in the Arctic, the Russian-born scientist has been involved in developing the physics driving global wave prediction models managed by the United States’ National Ocean and Atmospheric Administration (NOAA). His research is also helping scientists understand the ocean dynamics of tropical cyclones and the impact waves have on the ocean’s ability to store carbon dioxide and heat, as the world warms up.
Not just waves
While there are many oceanographers in Australia, Babanin says few investigate the effects waves bring to the climate system. “That’s our niche. It’s not just waves, it’s not just oceanography, it’s the wave-coupled effects.”
He explains that the missing factor in wave modelling is the physics that govern the interaction between waves and winds. Waves are generated by wind, but in turn the roughness of the sea surface changes the wind, which affects the meteorology over the ocean and the climate.
In tropical cyclones or hurricanes for instance, giant waves mix and churn up cold water from the deep ocean, changing the local current structure. An upwelling of cold water under the footprint of the cyclone can dampen it down or shut it off completely once the water reaches 26 degrees Celsius. Occasionally a downwelling can bring in warmer water and increase the power of the cyclone.
The waves produced by tropical cyclones or hurricanes are most destructive once they hit the coastline, as shown by Hurricane Sandy, which caused around US$70 billion damage in New York and New Jersey in 2012.
Babanin says our ability to predict the intensity of tropical cyclones has not improved for decades. This is due to enormous uncertainty about the dynamics of fluxes that go into the ocean and back into the atmosphere. For instance, scientists struggle to precisely measure ocean spray production.
To get more accurate measurements, Babanin negotiated with research partner Woodside Energy to set up a tropical cyclone observation site on their North Rankin Complex gas platform off Australia. “That’s the first field site which is equipped to measure the whole set of air interactions, the fluxes in the air, the fluxes in the water, the waves themselves and the spray,” says Babanin. They recorded the first tropical cyclone from the platform last summer.
Drawn to the sea
Babanin, who was brought up in Crimea on the Black Sea, was always fascinated by oceanography. He worked as a research scientist in Russia before migrating to Australia about 20 years ago. Appointed a Research Fellow at the Australian Defence Force Academy in Canberra, he worked on the landmark wind-wave field experiments conducted in the shallow Lake George, about 40 kilometres north-east of the city.
The research was headed by Professor Ian Young, who later became Vice-Chancellor of Swinburne university and then Australian National University. Young says the Lake George study, funded largely by the United States Navy, examined “all the forces that went towards generating waves” by mimicking how waves behave in coastal areas. While the lake is only around 1.5 metres deep, the dataset from this ideal field site is now used to forecast wave conditions across the world’s oceans.
“Particularly in the past five years, one of the very significant things that Babanin has been driving and building up is the new physics going into these global wave prediction models,” says Professor Young. Wave models consider the impact of a range of physical processes, which determine how waves evolve, such as energy input from the wind and energy loss due to wave breaking. “It is the understanding of these terms where Babanin has made his impact,” he says. In fact, Babanin updated around 60 per cent of the physics terms of NOAA’s new Wavewatch 111 model, which is used by national agencies such as the Australian Bureau of Meteorology for wave forecasting, as well as by industry, surfers, ships navigators and captains.
Young, now an Adjunct Professor at Swinburne, is researching extreme waves with Babanin. They were awarded an Australian Research Council grant to better understand and predict the most extreme storms, and the most extreme wave heights, as the climate changes.
Their modelling is based on the world’s most comprehensive wind and wave dataset, which Young compiled from 30 years of satellite imaging.
Already they have found that over the past 30 years the average wave conditions across the globe have increased by about four to five per cent. The data indicates that extremes are increasing. “So you’re getting more storms and more intense storms,” says Young.
The largest wind-generated waves could be 35 metres high. “I’ve certainly never been to sea in these conditions, but it would be simply terrifying,” he says.
Accurately predicting extreme waves is important for engineering and shipping. They intend using the dataset to simulate not just one in 100 year events but the highest waves that could occur in 1,000 or 10,000 years. The one in 10,000-year information is now demanded by some insurers of offshore gas rigs.
Perhaps more important in the near future is the role ocean waves play in climate change, says Young. Large amounts of heat from the atmosphere enter the oceans and, in many cases, mix into the deeper ocean. Young says the speed at which the ocean can take up carbon dioxide depends on the roughness of the ocean, so research into waves is “an important element of being able to build accurate models for what might happen to our climate in future”.
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