Climate change is rising winter waves in California, study finds

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Climate change has become a hot topic around the globe. Everyone talks about how our planet is heating up. This global warming affects us in many ways, one of which is the sea.

Peter Bromirski, a seasoned researcher from UC San Diego Scripps Institution of Oceanography, found that the height of winter waves in California has gone up. His study used data from the past 90 years to show this change.

A Look at the Waves Through Seismic Records

The surprising part is, Bromirski didn’t measure the wave heights directly.

Instead, he used an unusual but effective method. He looked at seismic records, which are data collected by machines that measure the shaking of the Earth, from as far back as 1931.

Bromirski had created this unique method in 1999. The longer the data, the more trustworthy the results. And this study had lots of data, spanning over nine decades!

The finding supports other research that says storms in the North Pacific Ocean have become stronger because of climate change.

If global warming continues to speed up, bigger winter waves could cause more flooding and erosion on the California coast.

How Does it Work?

You might be wondering how seismic records can tell us anything about waves. When waves get close to the shore, some of their energy bounces back into the sea.

When this bounced-back energy crashes into the incoming waves, it creates a strong downward push. This push turns into shaking energy at the seafloor, which can be picked up by machines called seismographs.

The shaking is stronger when the waves are higher. This is how Bromirski could figure out the wave height from the seismic records.

Cutting Through the Noise

Of course, there’s a catch. Seismographs pick up all kinds of shaking, not just the kind made by waves. They also record earthquakes.

But Bromirski said this isn’t a big problem. Earthquakes usually don’t last as long as ocean waves caused by storms. So, he could filter out the “noise” of earthquakes and focus on the waves.

Why Not Measure Waves Directly?

Now, you might ask, why didn’t Bromirski measure the wave heights directly? It’s because direct measurements haven’t been around for long.

The buoys that measure wave heights off the California coast started collecting data only in the 1980s.

But to understand changes in the sea due to climate change, we need many decades of data. And we’re particularly interested in the time before 1970, when global warming started to pick up speed. So, Bromirski had to look for other sources of data.

The Journey of a Researcher

Back in the 1990s, Bromirski started searching for other ways to get data on wave heights. In 1999, he found a way to figure out wave heights from modern digital seismic records and published his method.

During his research, he learned that UC Berkeley had seismic records going back nearly 70 years. But there was a problem. These records were all on paper, not digital.

To make use of these paper records, Bromirski and his team had to turn them into digital data. This wasn’t a quick job. It took the hard work of many students, a special scanner, and several years to complete.

The Result: Rising Waves

After the paper records were digitized, Bromirski finally had seismic data from 1931 to 2021. He turned this data into wave heights and started looking for patterns. What he found was quite alarming.

Since 1970, the average winter wave height in California has gone up by 13%. That’s about one foot.

Between 1996 and 2016, there were about twice as many big storms that made waves over 13 feet high compared to the period from 1949 to 1969.

Understanding the Implications

What does all this mean? It means that since 1970, when global warming started to speed up, there have been more big wave events.

It also means that there are fewer winters with low wave activity. And these changes match up with the speeding up of global warming.

Other research has also found a similar increase in wave height in the North Atlantic. So, this is not just a California thing.

If global warming continues, and winter waves keep getting bigger, it could make the effects of rising sea levels worse. This could mean more damage to the coast and to coastal buildings.

Studying the Storms

Bromirski also looked at weather patterns over the North Pacific, which is where California’s winter storms come from.

He found that a low-pressure system near Alaska’s Aleutian Islands, known as the Aleutian Low, has become stronger since 1970. A stronger Aleutian Low usually means stronger storms and waves.

In the end, the study warns us about a new problem we need to consider. If storms and waves keep getting stronger as the climate changes and sea levels rise, we need to prepare for more coastal damage in California and likely other parts of the world.

The study was published in the Journal of Geophysical Research Oceans.

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Source: University of California – San Diego