Waves reaching new heights as climate changes

UCSC researchers identify effects of global warming in wave strength

Increasing wave power is now being recognized by marine scientists as a potentially valuable climate change indicator, similar to global sea rise, rising temperatures and carbon dioxide concentration.

In addition to indications of a new signal of climate change, the wave energy is directly related to processes that drive coastal impacts with socioeconomic consequences such as those related to flooding or erosion, said Borja G. Reguero, of the University of California-Santa Cruz’s Institute of Marine Sciences.

“For the first time, we have identified a global signal of the effect of global warming in wave climate,” Reguero said. “In fact, wave power has increased globally by 0.4 percent per year since 1948, and this increase is correlated with the increasing sea-surface temperatures, both globally and by ocean regions.”

“This study shows that the global wave power can be a potentially valuable indicator of global warming, similarly to carbon dioxide concentration, the global sea level rise, or the global surface atmospheric temperature,” said coauthor Inigo J. Losada, who is the director of research at the University of Cantabria, in Spain, where the study was developed.

The research shows that global warming increases wave power globally, and for the Pacific, the warming of the tropical Pacific and the North Pacific will be the most influential, according to historical data, he said.

Reguero is the lead author of the study published on Jan. 14 in Nature Communications and also noted by EurekAlert, the online publication of the American Association for the Advancement of Science. 

While sea level rise puts coastal areas at the forefront of climate change impact, this new research points to other climate-related threats as well.

Analyses of global marine climate to date has identified increases in wind speeds and wave heights in localized areas of the ocean in high latitudes of both hemispheres, but until now a global signal of change and a correlation between the localized increases in wave heights and global warming had remained undetected, researchers said.

The UCSC team’s study focused on energy contained in ocean waves, which is transmitted from the wind and transformed into wave motion. This metric, called wave power, has been increasing in direct association with historical warming of the ocean surface. Upper ocean warming, measured as a rising trend in sea-surface temperatures, has influenced wind patterns globally, and this, in turn, is making ocean waves stronger, researchers said.

Understanding how the energy of ocean waves responds to oceanic warming has big implications for coastal communities, where infrastructure such as breakwaters and levees are needed as port, harbor and coastal defenses. As wave energy increases, its effects can become more profound, allowing more wave energy to reach shoreward, researchers said.

Effects of wave power increase are particularly apparent during storm seasons, such as those that occurred in the winter of 2013-14 in the North Atlantic, which impacted the west coast of Europe, or the 2017 hurricane season in the Caribbean.

What is crucial to Alaska is that this region already has some of the largest waves on the planet.

Reguero said he was uncertain whether this research would be used by the U.S. Army Corps of Engineers to help plan for more effective breakwaters in future years. Still, he is working on the design of international guidelines for design of natural and nature-based features, or nature -based solutions, led by the USACE, he said. The wave power is also critical for the state and evolution of coastal ecosystems including marshes and reefs, he said.

“How we design breakwaters needs to start factoring the effects of climate change, not only with the rising sea levels, but also increased wave action,” he said. “Coastal structures will have to be designed for future conditions, so they can keep up their original design levels.

“With respect to navigation, there is not much work done on how these changes could affect safety and navigation conditions, but it is definitely one major impact. Having a direct connection between upper ocean warming and the energy of waves is the first step. Understanding how the energy of ocean waves responses to oceanic warming has important implications for coastal communities, including anticipating impacts on infrastructure, in addition to coastal cities and small islands,” he said.

“Impacts include navigation safety, but also access to harbors and ports, condition and evolution of coastal ecosystems and other impacts such as flooding and erosion. As wave energy increases, its effects can become more profound. Sea level rise will also allow more wave energy to reach shoreward, which will have aggravated consequences,” he said.