Extreme ocean heat is boiling the Pacific Ocean off the coast of California, and experts warn it could affect coastal weather and ecosystems for months.
An ocean heat wave began building late last year but has worsened in recent weeks, according to readings at Scripps Pier in La Jolla, which has broken more than 25 daily temperature records so far this year. Wednesday’s surface water temperature was 68.5 degrees – 7.7 degrees above average for the day. The sea level was 67.6 degrees, the hottest April 15 in nearly a century of records.
The heat wave is deep, persistent and widespread, stretching from almost San Francisco to the Mexican border. Those are “very important indicators that this has the potential to last and will have effects for weeks or months or seasons to come in Southern California,” said Daniel Swain, a climate scientist for the University of California’s Agriculture and Natural Resources.
Beaches play in the water near the Hermosa Beach Pier.
There are several factors driving the incredible heat, including a persistent high-pressure system moving over Southern California and weaker-than-normal onshore winds, which tend to drive highs along the coast. Upwelling when cold, deep ocean water rises to the surface.
But human-caused climate change is undoubtedly pushing temperatures to new records, Swain said, noting that it takes many times more energy to heat ocean water than to heat air. “In terms of ocean warming, we’re now entering an incredible period” in this part of the world, he said.
El Niño may drive ocean warming even further in the coming months. The state’s latest outlook includes a 61% chance that El Niño will emerge between May and June and last through at least the end of the year, with a 1 in 4 chance of a particularly strong El Niño. A tropical Pacific climate pattern is associated with warm, wet conditions in Southern California.
This year’s El Niño will eliminate ocean heat, but once established, El Niño will help the ocean heat wave intensify and continue, said Dillon Amaya, a research scientist at the National Oceanic and Atmospheric Administration’s Physical Sciences Lab. He said current models are predicting at least a 70% chance that the sea heat will continue off the coast of Baja until December.
“There are places in the world where it’s easy to find large disturbances like this, especially the Gulf Stream or the Kuroshio Extension. [near Japan],” said Amaya, “But Baja is not one of those places. It’s not easy to find a puzzle of this magnitude, so in my mind it makes it all the more vivid – and frightening. ”
That’s because the phenomenon is reminiscent of the “blob” – a large ocean heat wave that gripped the Pacific Ocean off the coast of Western California from about 2014 to 2016. He has brought great disturbance to the marine environment: mass killing of seabirds, fishing disasters, destruction of kelp, dangerous fish migration, whale fish migration, dangerous fish migration, fish migration and domestic animals. they are blooming, said Amaya. That warm figure extended in patches along the West Coast and up into Canada and Alaska.
A warming Pacific Ocean can mean less ‘May Gray’ and ‘June Gloom.’
There are also potential impacts on land, such as a reduced sea level, because warmer water temperatures will make it harder for low-lying clouds and fog to grow over land. That means less of the “May gray” and “June gloom” many Southern Californians have come to expect, Amaya said.
Conditions could make the California coast feel more humid and windy due to the loss of cooling fog and because the warm air is holding more moisture, according to Swain. For Californians accustomed to dry heat, that can have potential health implications.
“Ninety degrees is not record-breaking heat, but 90 degrees with humidity is not something people in LA are really prepared for,” he said. The same goes for warm nighttime temperatures, which can occur with this system and can make it difficult for people’s bodies to cool down.
In addition, warmer ocean waters can increase the likelihood of hurricanes and tropical storms off the coast of Mexico. Although such storms are hundreds of miles away in southern California, the state could still experience remnants of those systems, as happened with Hilary in 2023, Swain said.
There is little certainty about the outcome of California’s wildfire season. While some storms and moisture can help prevent wildfires, there’s also a chance dry lightning could start them, he said.
Art Miller, a researcher at the Scripps Institution of Oceanography, said the West Coast also saw ocean warming in 2019, which he called “Blob 2.0.” That was set up in Northern California and the Gulf of Alaska, and led to major ecosystem disruption.
There is some concern that because these ocean heat waves in the north Pacific occur in the same way – but not exactly the same – as structures “like blobs,” they may be part of the Pacific Ocean’s larger adaptation to climate change driven by greenhouse gases from fossil fuel burning, Miller said, although “the observational record is not long enough to say this.”
“But there is clear evidence that the background average [sea surface temperature] is increasing in general in the oceans, apparently due to global warming, so that warm disturbances riding on that long-term warming are occurring on a much larger scale,” he said.
A girl plays in the water near the Hermosa Beach Pier.
Amaya, of NOAA, noted that the current ocean heat wave would likely have formed without climate change. But the overall temperature, and intensity, of the system, “is definitely a function of global warming.”
“As the world continues to warm, every ocean heat wave will be warmer than the last one,” he said.
