But determining whether that reading was in fact a world record is complicated. First things first: The buoy’s reading is so off-the-charts; could it have been malfunctioning? Allyson Gantt of the National Park Service, which monitors and maintains the buoy, said the data was consistent with high water temperatures in the area. Then, there’s the fact that there is no official keeper of ocean temperature records. The World Meteorological Organization tracks land surface temperature records, but not ones set at sea.
Experts have pointed to a reading of 99.7 F, recorded in the middle of Kuwait Bay in 2020 and reported in a 2020 research paper, as the world record to date. Still, comparing the Kuwait reading, taken in the open sea, to a reading in shallow waters off the coast of Florida could be tricky. Just like it’s easier to heat up a shallow bath than a deep one, the depth of the water is going to affect temperatures, said Jeff Masters, a co-founder of Weather Underground, a web-based weather service, said. Out in the open ocean, it’s rare for surface temperatures to rise above roughly 90F, beyond which the water usually evaporates, said Frank Edgar Muller-Karger, a marine science professor. Whether or not temperatures off Florida broke a world record, 100F is an alarming reading for seawater.
When sea temperatures rise too high, it causes corals to expel the algae they need for sustenance, a process known as bleaching. Corals experience the most heat stress in August and September. But the recent heat means they’re now becoming stressed much earlier in the year. If waters don’t cool quickly enough, or if bleaching events happen in rapid succession, the corals can die. By some estimates, the world has already lost half of its coral reefs since 1950. About 44% of the world’s oceans are experiencing a marine heat wave, experts say. And in Florida, as Masters put it: “If you took a dip in Manatee Bay, it would feel like a hot tub.”