Site icon Conservation news

Climate change is making waves stronger and putting coastlines at risk

  • According to research published in the journal Nature Communications this month, the energy of ocean waves has grown over the past seven decades, which could have significant implications for coastal communities and ecosystems.
  • The energy in ocean waves is transmitted from the wind. As the upper ocean has warmed, wind patterns have been affected globally, resulting in stronger ocean waves. The researchers behind the Nature Communications study say they found a long-term trend of wave power increasing globally in direct association with historical warming of the ocean surface.
  • The researchers say their results show that global wave power could be used as an indicator of global warming similar to how atmospheric carbon dioxide concentration levels, global sea level rise, or global surface atmospheric temperatures are used now.

Global climate change is impacting Earth’s oceans in a number of ways, from higher water temperatures and rising sea levels to acidification and oxygen depletion.

Now, scientists have reported another change to oceans  wrought by global warming: According to research published in the journal Nature Communications this month, the energy of ocean waves has grown over the past seven decades, which could have significant implications for coastal communities and ecosystems.

The energy in ocean waves is transmitted from the wind. As the upper ocean has warmed, wind patterns have been affected globally, resulting in stronger ocean waves. The researchers behind the Nature Communications study say they found a long-term trend of wave power increasing globally in direct association with historical warming of the ocean surface.

“For the first time, we have identified a global signal of the effect of global warming in wave climate,” Borja G. Reguero, a researcher in the Institute of Marine Sciences at the University of California, Santa Cruz in the United States and the study’s lead author, said in a statement. “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.”

Previous analyses of the global wave climate, or how wave characteristics change over time, have tended to focus on historical trends in mean and extreme values for parameters such as wave height, Reguero and co-authors note. Wave heights have increased in recent decades, especially at higher latitudes in both hemispheres.

“Satellite-based altimeter measurements from 1985 to 2008 reveal increases of 0.25% per year for the 90th wave height percentile and 0.50% per year for the 99th percentile, in both hemispheres,” the researchers write in the study. “[D]ata also show significant increases in extreme wave heights at the high latitudes of the southern hemisphere, 0.25–0.9% per year for the 90th percentile in the north Atlantic and the north Pacific, and decreases in the mid-latitudes.” In addition to changes in wave heights, wave periods have also increased, and the direction of waves has shifted in some cases, such as in the southern ocean and in the north Atlantic.

Changes in global wave energy have received less attention, the researchers say, “particularly in the context of climate change.” They add that wave power has not been studied as a climate change indicator yet, but they found that “it can potentially characterize the long-term behavior of the global wave conditions better than wave heights.”

Study co-author Inigo J. Losada, director of research at the Environmental Hydraulics Institute at Spain’s University of Cantabria, said that the study results show that global wave power could be used as an indicator of global warming similar to how atmospheric carbon dioxide concentration levels, global sea level rise, or global surface atmospheric temperatures are used now.

Understanding how global wave power responds to oceanic warming also has important implications for adapting coastlines to the impacts of climate change on infrastructure, coastal cities, and small islands. Wave power is a “key driver of coastal change and flooding,” the authors of the study write, and as wave energy increases, the effects will become more profound.

For instance, as sea levels rise, more wave energy will reach shore, exacerbating impacts to shorelines. But regional differences in upper-ocean warming will mean that wave power changes are different in each ocean basin. This variability in wave energy across regions and at different times of the year are most apparent in the heightened flooding and erosion risks to Pacific coastlines during El Niño events, “which are explained by our [wave power] patterns,” according to the authors. “Regionally, changes in the extratropical generation areas of the Southern Ocean and North Pacific, where the [wave power] is more severe, should receive special attention.

“Our results indicate that risk analysis neglecting the changes in wave power and having sea level rise as the only driver may underestimate the consequences of climate change and result in insufficient or maladaptation,” co-author Fernando J. Méndez, associate professor at Universidad de Cantabria, said in a statement.

CITATION

• Borja G. Reguero, Iñigo J. Losada, & Fernando J. Méndez. (2019). A recent increase in global wave power as a consequence of oceanic warming. Nature Communications 10. doi:10.1038/s41467-018-08066-0

Featured Image: Photo by Michael Goyberg.