Warming Oceans Are Making Waves Stronger With Every Passing Year

Ocean waves are the canaries in Earth’s coal mine, signaling disaster before the worst effects arrive. According to a study published Tuesday in Nature Communications, ocean waves are becoming increasingly powerful, a reality that has severe implications for coastal communities. This rise in wave power, scientists say, is directly linked to the warming of the ocean surface. Waves are a visual manifestation of climate change, and as the ocean heats up, they’ll only become stronger.

Scientists determined that wave power, which is the transport of the energy the wind transfers into sea-surface motion, has increased globally by 0.4 percent per year since 1948. And wave power is increasing in direct correlation with the increasing sea surface temperature, both globally and by ocean subregions. Study co-author and University of California, Santa Cruz researcher Borja Gonzalez Reguero, Ph.D. tells Inverse that this new information categorizes wave power as a new indicator of climate change, similar to global sea level rise or the increase in CO2 concentration.

“Ocean heating is a critical marker of climate change,” Reguero says. “Our study shows that this is affecting ocean-atmosphere interactions, and in turn winds and the waves they generate, which reach our shores.”

Reguero’s research emerged alongside multiple recent studies demonstrating that human-driven climate change is altering the ocean for the worse. Earlier in January, researchers announced in Science that ocean warming is actually stronger and more consistent than scientists had previously estimated. On Tuesday, the authors of that study released another paper in Advances in Atmospheric Sciences showing that 2018 was the hottest year ever recorded for the global ocean. The Guardian estimated from the data that for the past 150 years, climate change has heated the oceans by the equivalent of 1.5 atomic bomb explosions per second.

Reguero and his team are the first to examine the relationship between climate change and wave power. Previously, climate scientists focused on increases in wind speeds and wave heights — both of which are increasing. Studying wave power adds the benefit of understanding how the ocean’s energy has changed over cumulative periods of time, and in the opinion of this team, it is a better indicator of the long-term variation of wave climate.

The team incorporated satellite data that encompassed wave heights and mean wave periods, statistical modeling, historical wind-wave datasets, and yearly measurements of the ocean’s spatiotemporal sea surface temperature to determine that upper-ocean warming, as a consequence of anthropogenic climate change, is causing waves to become stronger.

The effects of this change were seen during the winters of 2013 and 2014, when a sequence of storms produced heavy damages from flooding and erosion in the west coast of Europe. These storms weren’t powerful because wave heights were particularly high. They were powerful because of their long wave periods, which were fueled by high-energy conditions.

According to Reguero, these changes in wave energy will have a direct effect on coastal communities because wave energy affects sediment transport, wave run-up, coastal erosion, and flooding. As cities begin to figure out how to adapt to climate change, they’ll need to consider wave energy alongside sea level rise if they want to stay afloat.

“Understanding how wave climate has changed and will change in the future has important implications for coastal adaptation, including anticipating impacts on infrastructure,” Reguero says. “Risk analyses that only consider sea level rise and its impacts may be underestimating the consequences of climate change in coastal areas.”