We're all familiar with the idea of a heatwave, those sweltering days when the air is thick and the sun relentless. But there's another type of heatwave that's much less visible yet equally concerning: a marine heatwave.

Marine heatwaves are periods of unusually warm ocean temperatures that can last anywhere from days to months. Just recently, an intense marine heatwave has arrived just offshore the north and central California coast, pushing water temperatures up to 7°F above their typical levels. A buoy near the Golden Gate reported an astounding 68°F, making it 7°F above what's considered normal for this time of year.

Should we be concerned?

Warmer waters due to marine heatwaves can severely impact marine ecosystems, creating nutrient-deficient "ocean deserts" that make it challenging for marine life to survive. These temperature spikes are linked to a range of disruptions, from coral bleaching and altered fish migration patterns to the degradation of vital kelp forests along the coast.

The most recent example of an extreme marine heatwave occurred off the coast of South Florida. On July 24, a buoy in Manatee Bay, just north of Key Largo, recorded a staggering sea surface temperature of 101.1°F, potentially breaking the previous world record of 99.7°F set in Kuwait Bay.

Another consequence of marine heatwaves is heightened humidity, resulting in muggier conditions along coastal areas. This added moisture exacerbates discomfort and provides extra fuel for storms.

In the Pacific, for example, elevated water temperatures can intensify tropical cyclones and atmospheric river events. Tropical Storm Hilary serves as a recent example, illustrating how above-average temperatures can both amplify and expand the reach of such weather phenomena.

While ocean heatwaves are a natural occurrence in Earth's oceans, those that are exceptionally warm or prolonged, such as the one occurring off the West Coast this week, can have devastating effects on both local wildlife and human communities. Oceanographers and marine biologists are closely monitoring these events to better understand their immediate and long-term impacts.