California's record-breaking ocean heatwave defies expectations

A prolonged marine heatwave gripping the waters off california's coast has raised alarm bells among scientists, who warn that the extreme warmth could have devastating impacts on marine life and ecosystems.

Unprecedented temperatures

For over a century, the Scripps Institution of Oceanography has operated shoreline stations to monitor water temperatures. This year, they've repeatedly recorded daily highs that shatter historical records – with the La Jolla station hitting temperatures 10°F above average in January.

The heatwave is not driven by El Niño, the typical warm-water current that periodically affects the Pacific. Instead, a persistent high-pressure system has parked over southern california, warming both the air and sea to historic levels.

This phenomenon, reminiscent of the notorious 'Blob' marine heatwave of 2013-2016, has drawn comparisons to that devastating event. 'The biggest concern is how the year plays out,' says Andrew Leising, an oceanographer with the National Oceanic and Atmospheric Administration. '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.'

While the heatwave has brought warmer water temperatures, it also threatens to disrupt the delicate balance of california's marine ecosystems. Prolonged ocean warmth can devastate phytoplankton, the base of the marine food chain, leading to harmful algal blooms and wreaking havoc on a wide range of marine species, from sea lions to halibut.

Researchers are still working to understand the drivers behind these extreme events, which are becoming more frequent and prolonged due to the slow warming of the oceans and atmospheric changes.

However, there are some silver linings. The warmer waters attract tuna closer to shore, making them easier to catch, and surfers and swimmers have enjoyed the unusually warm ocean temperatures.

But as Melissa Carter, a researcher at the UC-San Diego Scripps Institution of Oceanography, cautions, 'Our ocean should not be a swimming pool. Nothing can live in a swimming pool. That's not what we want.'