California’s king tides offer a peek at a warmer planet

Dr. Michael Quill stands atop a beachside staircase that’s mostly buried in sand, poised to take a picture of the next big wave. As the tide rolls in, it crashes beneath a few oceanfront homes in Malibu and sprays their second-floor balconies. The seafoam nearly hits Quill, stopping a couple stairs shy of him as he holds up his phone and takes the shot.

This disappearing shoreline is called Broad Beach, but at high tide, it’s anything but.

Quill got up early along with scientists and volunteers up and down the California coast to grab hundreds of pictures of the edge of the surf during the first weekend in December, because that was the highest tide of the year, also known as the king tide. King tides usually happen once or twice per year, when the earth is at its closest point to the sun, while the moon is at its closest point to the earth.

Scientists consider king tides to be a window into the future as sea levels continue to rise. Places that flood only during king tides now might not be habitable in 100 years.

Quill and the other volunteers send their photos off to the California Coastal Commission, which produces a map with all the pictures they’ve collected.

As he stands on the staircase that cuts through the rock wall that protects homeowners from the shrinking beach, Quill gestures five houses down and observes, “From where the rocks are to this property is just dwindling away, dwindling away, dwindling away.”

“The high tide line goes right up to the people's property line,” he says. “I'd be kind of concerned if I'm sitting there in that house, and the water is going under three quarters of my house. I mean, it's just a matter of time.”

Since the late 19th century, the global sea level has already risen by about nine inches. If we manage to keep global temperature rise to the 1.5 degrees Celsius everyone agreed to at the recent U.N. Climate Change Conference (COP26) in Glasgow, then sea levels will likely rise another 10 inches.

If we do a bad job and don’t curb our emissions, it could be another eight feet in a worst-case scenario. And that puts a lot of coastal areas under water.

A window to the future

Volunteers are taking pictures of the king tides now, so that environmental scientists who specialize in sea level rise can figure out what to do next.

“There's nothing like getting real evidence from the ground to show you where the water is going to go,” says environmental scientist Carey Batha with the California Coastal Commission.

She says evidence has revealed that it’s not just a problem for coastal residents.

Recent research out of UC Berkeley found that 145,000 residents live near a hazardous facility that’s at risk of flooding by 2100 as sea levels rise. LA and Orange Counties have some of the highest number of sites at risk in the state. Long Beach is full of them, including the port, landfills, and the Wilmington Refinery.

“An evil twin of sea level rise is that the coastal groundwater table will also rise,” says Batha. “There might be pollutants buried in the soil that haven't been exposed to water for a really long time. And when groundwater rises, those pollutants could be mobilized.”

Disadvantaged communities are six times more likely to live near those facilities at risk of flooding, UC Berkeley researchers found.

For now, those risks are temporary. The king tide only lasts about an hour. But environmental scientists like Batha are already learning how to mitigate how much the water rises, and plan for a future when it inevitably does.

“Sea level rise is making us face unprecedented challenges,” she says. “But I think that when it comes down to it, we all love our shoreline, and we want it to continue to be safe and resilient.”