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Climate change is making ocean waves more powerful, threatening to erode many coastlines


Sea level rise isn't the only way climate change will devastate the coast. Our research, published today, found it is also making waves more powerful, particularly in the Southern Hemisphere.


We plotted the trajectory of these stronger waves and found the coasts of South Australia and Western Australia, Pacific and Caribbean Islands, East Indonesia and Japan, and South Africa are already experiencing more powerful waves because of global warming.


This will compound the effects of sea level rise, putting low-lying island nations in the Pacific—such as Tuvalu, Kiribati and the Marshall Islands—in further danger, and changing how we manage coasts worldwide.


But it's not too late to stop the worst effects—that is, if we drastically and urgently cut greenhouse gas emissions.


An energetic ocean


Since the 1970s, the ocean has absorbed more than 90% of the heat gained by the planet. This has a range of impacts, including longer and more frequent marine heatwaves, coral bleaching, and providing an energy source for more powerful storms.


But our focus was on how warming oceans boost wave power. We looked at wave conditions over the past 35 years, and found global wave power has increased since at least the 1980s, mostly concentrated in the Southern Hemisphere, as more energy is being pumped into the oceans in the form of heat.


And a more energetic ocean means larger wave heights and more erosive energy potential for coastlines in some parts of the world than before.


Ocean waves have shaped Earth's coastlines for millions of years. So any small, sustained changes in waves can have long-term consequences for coastal ecosystems and the people who rely on them.


Mangroves and salt marshes, for example, are particularly vulnerable to increases in wave energy when combined with sea level rise.


To escape, mangroves and marshes naturally migrate to higher ground. But when these ecosystems back onto urban areas, they have nowhere to go and die out. This process is known as "coastal squeeze".

These ecosystems often provide a natural 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.

So why is this happening?


Ocean waves are generated by winds blowing along the ocean surface. And when the ocean absorbs heat, the sea surface warms, encouraging the warm air over the top of it to rise (this is called convection). This helps spin up atmospheric circulation and winds.

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