For over a hundred years, the Scripps Institution of Oceanography has operated coastal stations that monitor water temperatures along California’s shoreline. However, this year, these stations are indicating troubling signs.
In recent months, numerous stations have consistently recorded unprecedented daily high temperatures, with the La Jolla station observing temperatures that soared 10 degrees Fahrenheit above the historical average at one point last month.
Typically, the waters off Southern California experience periodic warming every few years due to tropical currents associated with El Niño. Nevertheless, the current marine heatwave that began last fall is not a result of these tropical influences. Instead, a high-pressure atmospheric system, characterized by clear and sunny conditions, has settled over Southern California, leading to elevated air and sea temperatures well beyond normal. This same weather pattern has contributed to an intense heatwave on land in California.
This prolonged oceanic warming has drawn parallels to a past event known as “the Blob,” a three-year marine heatwave triggered by similar extended high-pressure systems a decade ago, which had a detrimental effect on marine ecosystems. Scientists believe that the coming weeks will be critical in determining whether the current heatwave will diminish or escalate into a situation akin to the Blob.
Andrew Leising, an oceanographer at the National Oceanic and Atmospheric Administration, expressed concern about the potential implications of this year’s conditions, stating, “The biggest concern is how the year plays out. If it remains warm and is followed by a strong El Niño, we could see much larger impacts next fall and winter.”
During spring, it is common for changes in atmospheric conditions to produce northwesterly winds, which push warm surface waters back into the ocean and allow cooler waters from below to rise—an occurrence known as upwelling. This upwelling process brings nutrient-rich waters to the surface, supporting phytoplankton, which are vital for California’s marine life.
Recently, there have been signs of a slight cooling in high water temperatures, suggesting that the heatwave may be beginning to subside. However, it will take time to confirm if the warmth is truly dissipating.
Leising noted, “The expectation right now is that the waters down to even southern California should start cooling a little bit into next month, but it’s not a guaranteed thing. The concern is the sequence of events and how they unfold.”
Extended periods of elevated ocean temperatures can severely impact phytoplankton populations and lead to harmful algal blooms, which can disrupt various marine species, including sea lions, dolphins, shorebirds, and halibut. Melissa Carter, a researcher at the UC-San Diego Scripps Institution of Oceanography, pointed out that the years affected by the Blob saw one of the worst Dungeness crab seasons in recent times.
These marine heatwaves are becoming increasingly frequent and longer-lasting, partially due to the gradual warming of the oceans driven by climate change, as well as atmospheric shifts that scientists are still working to comprehend.
Carter raised an important question: “What’s causing us to have these extreme warm temperatures? What are the drivers? That’s what we’re trying to find out.”
She expressed concern that once high-pressure systems become established in a region, they can create a “feedback loop” that reinforces warm, calm conditions, which diminishes the likelihood of upwelling occurring. “If these systems do become that strong and persistent, where they come every year, it can have the potential to shut down upwelling,” she warned. “Everything we think of related to the health of the ecosystems of the west coast could be forever altered.”
While the persistent ocean heat does present a few benefits, such as bringing tuna closer to shore for easier fishing and providing warmer water for surfers and swimmers during winter, these advantages are far outweighed by the potential negative consequences. “I enjoy being in the water when it’s a marine heatwave,” Carter said. “But our ocean should not be a swimming pool. Nothing can live in a swimming pool. That’s not what we want.”
