Seawater off the Southern California coast is warmer than normal. What does that mean?

On Aug. 1, scientists measuring the sea surface temperature of ocean water at Scripps Pier in La Jolla recorded the warmest temperature since 1916: 78.6 degrees.

Two days later, the record was broken again: 78.8 degrees.

And on Wednesday, the record was again shattered at 79.2 degrees.

“It’s not a single record-breaking temperature that really matters, it’s the repeated occurrence of above-average temperatures over weeks, months, seasons, years that’s really troubling,” Art Miller, a climate, atmospheric science and physical oceanography researcher at Scripps Institution of Oceanography told The Tribune. “Over time in general, the temperature off the pier has gotten warmer and warmer.”

The warm sea surface temperatures are just affecting Southern California for now — from the San Diego region up through Point Conception, north of Santa Barbara.

Past that area, the seawater is about the temperature it should be — even a little below average for this time of year, according to PG&E meteorologist John Lindsey.

Waters near the Diablo Canyon Nuclear Power Plant are measuring on average at 53.5 degrees, Lindsey said. Usually, the average seawater temperature in early August is about 56.62 degrees, he said.

That’s because northwesterly winds blowing over the Pacific Ocean, from the Oregon border and southward, create “upwelling,” which means cooler, nutrient-rich ocean water comes up from the deep and mixes with warm water on the surface, which keeps the water at the surface cold.

However, those winds start to get blocked off around Point Conception, when the coastline starts moving further inland, Lindsey said.

“There’s a real dramatic temperature gradient between north of Point Conception and south of Point Conception,” Lindsey said. “Just over a couple of miles, the temperature change is more than 10 degrees which is one of the strongest temperature gradients I’ve ever seen.”

Miller said that usually, in spring and early summer, some of those northwesterly winds make it past Point Conception and blow down the coast, creating upwelling that keeps the water cool. But this year, the winds shut down in June and July: “way ahead of time.”

Those northwesterly winds stopped due to “anomalous” high air pressure on land that also blocked a lot of local winds, Miller said. That means there was less wind all around to help mix cooler water with warmer water. It also means that the high air pressure, which is causing high heat on land, is also causing high temperatures in the ocean.

In fact, earlier in the week San Diego experienced its third heat wave in about a month, according to the San Diego Union-Tribune.

The warm water could affect the ocean ecosystem, Miller said, noting that harmful algal blooms like growing in warm water, and the blooms release toxins that can be absorbed by crabs, shellfish and other sea creatures.

“We don’t know how the ecosystem is going to respond here,” Miller said. “There could be fundamental changes in the way our ecosystem is flowing off our coast here.”

Miller noted that the situation is “not as critical as it would be” if the warm water was observed along the entire California coast, but said the warm water events are happening more frequently, and ride on an “ever-increasing trend.”

“We happened to hit these record-breaking temperatures early in August, I’ve never seen them hit that temperature,” Miller said. “The fact they hit 78 (degrees) and did it for multiple days, that’s amazing.”

This story was originally published August 8, 2018 at 4:20 PM with the headline "Seawater off the Southern California coast is warmer than normal. What does that mean?."