Surging waves threaten Australia coastline, warns researcher

Even small, sustained changes in waves could have long-term consequences for coastal ecosystems and the people who rely on them.
Even small, sustained changes in waves could have long-term consequences for coastal ecosystems and the people who rely on them.PHOTO: AFP

SYDNEY (XINHUA) - Ocean waves in the Southern Hemisphere are becoming more powerful and are exacerbating Australia's coastal erosion, according to an international team of oceanographic and environmental scientists.

Dr Tom Mortlock, an environmental scientist with Australia's Macquarie University, said his team plotted the trajectory of stronger waves and found the coasts of South Australia and Western Australia along with Pacific and Caribbean Islands were experiencing more powerful waves because of global warming.

Dr Mortlock, who also works for Risk Frontiers, a company that monitors and predicts the impact of natural disasters and environmental changes, believes the waves along with rising sea levels were putting low-lying island Pacific nations such as Tuvalu and Kiribati in even further danger.

The paper, Natural Variability and Warming Signals in Global Ocean Wave Climates, was published in May on the Advancing Earth and Space Science journal. Its authors included Itxaso Odériz and Professor Rodolfo Silva of the National Autonomous University of Mexico, and Professor Nobuhito Mori of Kyoto University.

Speaking to Xinhua on Tuesday (June 14), Dr Morlock said although rising sea levels were a long-term environmental problem, the impact of more powerful waves was more immediate.

"The key point of our study is that warmer ocean waters are the mechanism that causes these waves," he said.

Writing in The Conversation media outlet, the scientists noted that since the 1970s, the ocean had absorbed more than 90 per cent of the heat gained by the planet.

This caused a range of impacts, including longer and more frequent marine heatwaves, coral bleaching such as in the Great Barrier Reef, and provided an energy source for more powerful storms.

The team looked at wave conditions over the past 35 years and found global wave power had increased particularly in the Southern Hemisphere, as more energy was being pumped into the oceans in the form of heat.

Even small, sustained changes in waves could have long-term consequences for coastal ecosystems and the people who rely on them, they found.

Mangroves and salt marshes, for example, are vulnerable to increases in wave energy when combined with rises in sea levels. These fragile ecosystems often provide a buffer to wave attack for low-lying coastal areas.

"So without these fringing ecosystems, the coastal communities behind them will be exposed to more wave energy and, potentially, higher erosion," they wrote.

They described the situation as a "cascade of impacts", with warmer sea surface temperatures bringing about stronger winds, which alter ocean wave conditions.

The team warned that if warming continues at the present rate over the coming century, "we can expect to see more significant changes in wave conditions along the world's coasts than uncovered in our backward-looking research."

They added that changes to wave patterns towards the equator are more driven by ocean warming from man-made climate change, as opposed to those towards the poles, which tend to be affected by natural climate variability.

The team, however, said if greenhouse warming was kept in line with the guidelines of the Paris Agreement on climate change, wave patterns could still remain within the bounds of natural climate variability.