Max Darrow reports from San Francisco: coastal waters off California have smashed heat records for 38 days so far this year, and scientists warn the warm spell could last for months and spark a stormy, dangerous summer.
A sprawling marine heat wave stretches roughly 1,500 miles from Northern California down to Mexico and farther into the Pacific. Surfers and swimmers are already noticing the difference — in sunny San Diego, one local said he could trade his wetsuit for trunks well before summer. Researchers say these conditions have persisted since December, with sea temperatures running about 4 to 8 degrees higher than normal for this time of year.
Melissa Carter of the Scripps Institution of Oceanography, which operates a century-long program of daily coastal temperature records, says the central concern is duration. A stubborn high-pressure pattern has blocked the upwelling of deep, cool water that normally moderates coastal temperatures, allowing unusually warm surface waters to build.
The heat is producing visible and worrying impacts along the coast. Dead birds are washing ashore, likely starving after a collapse of food chains that begins with microbes and works up to forage fish. Scientists warn that kelp forests and large marine mammals such as whales could be imperiled. In addition, warmer waters encourage harmful algal blooms that can release toxins and deplete oxygen, potentially devastating whole ecosystems.
Offshore measurements come from autonomous ocean robots called gliders, deployed by researchers including Dan Rudnick, which are tracking temperature and other conditions beyond the coastline.
Forecasters are also watching the tropical Pacific: many models suggest an El Niño could develop. If warm equatorial waters shift northward during an El Niño year, they could reinforce the existing marine heat wave. Warmer ocean surfaces can also intensify hurricanes and strengthen atmospheric rivers, meaning that if El Niño materializes, California may face heightened risk of extreme weather events this summer — from stronger storms to increased flooding — compounding the ecological and public-safety threats posed by the unusually warm ocean.