Researchers at the National Oceanic and Atmospheric Administration say marine heat waves are on track to affect an unprecedented swath of the world's oceans this year.
NOAA defines a marine heat wave as a persistent period of "anomalously warm" ocean temperatures.
A record 40% of surface temperatures worldwide already qualify, and NOAA's model forecasts that as much as 50% of the world's oceans could experience such a heat wave by September, and stay that way through the end of 2023.
Researchers say the widespread heat is out of the ordinary. Usually, about 10% of the oceans would experience such conditions.
"In our 32-year record, we have never seen such widespread marine heatwave conditions," said Dillon Amaya, a research scientist at NOAA's Physical Sciences Laboratory. "It’s remarkable to reach 40% or 50%, even with long-term warming."
Extended periods of high ocean temperatures can play havoc with marine ecosystems. A heatwave can cause animal die-offs, bleach corals and prompt harmful algae blooms. It can disrupt fisheries and recreation, and it can fuel stronger tropical storms and hurricanes.
Typically, Amaya says, warmer seas could drive stronger storms that intensify more quickly. This year, however, ongoing El Nino conditions may introduce more chances for wind shear that can prevent storms from organizing and strengthening.
"Only time will tell whether one process dominates or if they will cancel each other out and we end up with an average hurricane season," Amaya said.
NOAA says its models are still in the experimental phase, but it hopes to ultimately build a trustworthy predictor for communities and economies that depend on the oceans.
Until then, the agency cautions, the heat wave forecast should not be used for emergency planning or other decisions. Instead, consult operational forecasts, like those that the National Weather Service and National Hurricane Center issue during weather events.
