Record Ocean Temperatures Off Southern California Spark Fears of Prolonged Marine Heatwave
For over a century, shoreline stations operated by the Scripps Institution of Oceanography have meticulously measured water temperatures along the California coast. This year, these stations are flashing a stark warning sign, with several posting record-breaking daily high temperatures over the last three months. Notably, the La Jolla station registered temperatures a full 10 degrees Fahrenheit above historical averages at one point last month, signaling an alarming trend.
Unusual Causes Behind the Warming Waters
Historically, the waters of southern California warm every few years due to tropical currents moving north, a phenomenon known as El Niño. However, the marine heatwave that began last fall has a different origin. Instead of tropical currents, a high-pressure atmospheric system has settled above southern California, bringing calm, sunny days that warm both air and sea to unprecedented levels. This same system has contributed to a severe heatwave on land, exacerbating concerns about climate impacts.
Comparisons to 'the Blob' and Potential Consequences
The extended ocean warming has drawn comparisons to "the Blob," a three-year marine heatwave a decade ago caused by similar prolonged high-pressure conditions that devastated marine life. Scientists warn that the next few weeks will be critical in determining whether this heatwave dissipates or evolves into something more severe. Andrew Leising, an oceanographer with the National Oceanic and Atmospheric Administration, expressed concern, stating, "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."
Disruption of Marine Ecosystems and Upwelling
Typically, shifting atmospheric conditions in spring generate north-westerly winds that push warm surface water out to sea, allowing cooler, nutrient-rich water from below to rise—a process called upwelling. This upwelling is vital for phytoplankton, which support much of California's marine life. However, the current high-pressure system threatens this natural cycle. Melissa Carter, a researcher at the UC-San Diego Scripps Institution of Oceanography, explained that these systems can create a "feedback loop" reinforcing warm conditions, making upwelling less likely. "If these systems do become that strong and persistent, where they come every year, it can have the potential to shut down upwelling," she said. "Everything we think of related to the health of the ecosystems of the west coast could be forever altered."
Devastating Impacts on Marine Life
Prolonged ocean heat has devastating effects, including harming phytoplankton and causing harmful algal blooms. These changes can wreak havoc on marine life, from sea lions and dolphins to shore birds and halibut. Carter noted that the Blob years led to one of the worst Dungeness crab seasons in recent history, highlighting the economic and ecological toll. Such heatwaves are becoming more common and lasting longer, partly due to the slow warming of oceans driven by the climate crisis and partly because of atmospheric changes that scientists are still working to understand.
Short-Term Benefits Versus Long-Term Costs
While the lingering ocean heat offers some short-term benefits, such as bringing tuna closer to shore for easier fishing and providing warmer water for surfers and swimmers, these pale in comparison to the long-term costs. Carter emphasized, "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."
Uncertain Future and Ongoing Research
Recent days have seen a slight cooling of water temperatures, raising hopes that the heatwave may be dissipating. However, it will take more time to confirm this trend. Leising cautioned, "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 concern is the sequence of events and how they unfold." Researchers like Carter are actively investigating the drivers behind these extreme temperatures, asking, "What are the drivers? That’s what we’re trying to find out," as they seek to better predict and mitigate future marine heatwaves.
