California's ocean heatwave: a blob resurgence?
Southern California’s coastline is experiencing an unnerving surge in water temperatures, triggering alarms within the Scripps Institution of Oceanography and raising fears of a repeat of the devastating marine impacts seen a decade ago during the “Blob” event. The readings, exceeding historical averages by as much as 10 degrees Fahrenheit last month, aren't attributable to the typical El Niño currents; something else is at play.
An atmospheric anomaly fuels the heat
For over a century, Scripps stations have diligently charted these waters. Now, they’re flashing a stark warning. The culprit isn't the usual influx of tropical currents. Instead, a persistent high-pressure system – those famously picture-perfect, sunny days – has stubbornly settled above Southern California, trapping heat both in the air and, critically, in the ocean. This same atmospheric setup has also fueled the region's recent intense heatwave on land, demonstrating a complex interplay between atmospheric and marine conditions.
The comparison to “the Blob,” a prolonged marine heatwave of 2014-2016, is unavoidable. That earlier event, also driven by similar high-pressure patterns, wreaked havoc on marine ecosystems, leading to widespread mortality and collapsing fisheries. Andrew Leising, an oceanographer with NOAA, cautions that the next few weeks are pivotal. “The biggest concern is how the year plays out,” he stated. “We could be looking at much larger impacts next fall and winter, if it stays warm and then it’s followed by a strong El Niño.”
Upwelling disrupted, ecosystems threatened
Typically, spring brings a natural reprieve: shifting winds that push warm surface water outward, allowing cooler, nutrient-rich water from the depths to rise—a process called upwelling. This upwelling is the lifeblood of California’s marine ecosystem, feeding the phytoplankton that underpin the food web. But with the persistent high-pressure system suppressing winds, upwelling has been severely limited, starving these vital organisms.
While temperatures have cooled slightly in recent days, offering a glimmer of hope, it remains uncertain whether this is a temporary fluctuation or the beginning of a sustained decline. Leising acknowledges the uncertainty. “The expectation right now is that likely the waters down to even southern California should start cooling a little bit into next month, but it’s not a guaranteed thing.”
The consequences are already being felt. Prolonged heat leads to harmful algal blooms and decimates phytoplankton populations, impacting everything from sea lions and dolphins to shorebirds and halibut. Melissa Carter, a researcher at Scripps, points to the disastrous Dungeness crab seasons experienced during the Blob years as a stark warning. The situation is further complicated by a potential “feedback loop,” Carter explains. Once these high-pressure systems establish themselves, they can reinforce warm conditions, making upwelling even less likely.
The long-term implications are staggering. “If these systems do become that strong and persistent, where they come every year, it can have the potential to shut down upwelling,” Carter warns. “Everything we think of related to the health of the ecosystems of the west coast could be forever altered.”
There are, of course, a few fleeting silver linings. Warmer waters have brought tuna closer to shore, easing fishing pressure, and surfers have enjoyed extended periods of pleasant water temperatures. But as Carter wryly adds, “I enjoy being in the water when it’s a marine heatwave. But our ocean should not be a swimming pool. Nothing can live in a swimming pool. That’s not what we want.”