#ocean warming

This is why graphs like this matter. Not because they prove that catastrophe is inevitable, and not because they predict the precise sequence of events over coming years. Science rarely deals in absolutes. What they show is that Earth is moving beyond the range within which modern human civilisation developed. We’re entering climatic conditions that our infrastructure, ecosystems, economies and institutions were never designed to accommodate.

Chronic ocean heating is fuelling a “staggering and deeply concerning” loss of marine life, a study has found, with fish levels falling by 7.2% from as little as 0.1C of warming per decade.

Researchers examined the year-to-year change of 33,000 populations in the northern hemisphere between 1993 and 2021, and isolated the effect of the decadal rate of seabed warming from short shifts such as marine heatwaves. They found the drop in biomass from chronic heating to be as high as 19.8% in a single year.

“To put it simply, the faster the ocean floor warms, the faster we lose fish,” said Shahar Chaikin, a marine ecologist at the National Museum of Natural Sciences in Spain and the study’s lead author.

“A 7.2% decline for every tenth of a degree per decade might sound small,” he added. “But compounded over time, across entire ocean basins, it represents a staggering and deeply concerning loss of marine life.”

The study, published in Nature Ecology & Evolution on Wednesday, also found marine heatwaves were leading to short-term booms in some populations that masked long-term harm from climate breakdown.

For instance, a heatwave that could cause sprat populations to fall in the Mediterranean Sea, which is at the warm edge of their natural range, would lead to a boom in the North Sea, at the cold edge of their range.

Fish in cold areas are better able to capitalise on these shifts than those in warm areas, the researchers found, but these temporary cold-water gains mask “widespread loss” due to ocean warming.

Carlos García-Soto, a scientist at the Spanish National Research Council and co-author of the UN’s world ocean assessment, said the study revealed a “concerning” dynamic for ocean governance.

Chronic ocean heating is fuelling a “staggering and deeply concerning” loss of marine life, a study has found, with fish levels falling by 7.2% from as little as 0.1C of warming per decade. Researchers examined the year-to-year change of 33,000 populations in the northern hemisphere between 1993 and 2021, and isolated the effect of the decadal rate of seabed warming from short shifts such as marine heatwaves. They found the drop in biomass from chronic heating to be as high as 19.8% in a single year. “To put it simply, the faster the ocean floor warms, the faster we lose fish,” said Shahar Chaikin, a marine ecologist at the National Museum of Natural Sciences in Spain and the study’s lead author. “A 7.2% decline for every tenth of a degree per decade might sound small,” he added. “But compounded over time, across entire ocean basins, it represents a staggering and deeply concerning loss of marine life.” The study, published in Nature Ecology & Evolution on Wednesday, also found marine heatwaves were leading to short-term booms in some populations that masked long-term harm from climate breakdown. For instance, a heatwave that could cause sprat populations to fall in the Mediterranean Sea, which is at the warm edge of their natural range, would lead to a boom in the North Sea, at the cold edge of their range. Fish in cold areas are better able to capitalise on these shifts than those in warm areas, the researchers found, but these temporary cold-water gains mask “widespread loss” due to ocean warming.

...heat-driven die-offs is now underway. A study published on Tuesday showed that more than half of the world’s coral reefs were bleached between 2014-2017 -- a record-setting episode now being eclipsed by another series of devastating heatwaves. The analysis concluded that 51 percent of the world’s reefs endured moderate or worse bleaching while 15 percent experienced significant mortality over the three-year period known as the “Third Global Bleaching Event”. It was “by far the most severe and widespread coral bleaching event on record”, said Sean Connolly, one the study’s authors and a senior scientist at the Panama-based Smithsonian Tropical Research Institute. “And yet, reefs are currently experiencing an even more severe Fourth Event, which started in early 2023,” Connolly said in a statement. When the sea overheats, corals eject the microscopic algae that provides their distinct colour and food source. Unless ocean temperatures return to more tolerable levels, bleached corals are unable to recover and eventually die of starvation. “Our findings demonstrate that the impacts of ocean warming on coral reefs are accelerating, with the near certainty that ongoing warming will cause large-scale, possibly irreversible, degradation of these essential ecosystems,” said the study in the journal Nature Communications.

The marine heat wave that gripped Florida in 2023 was hotter than anything the state has seen in 150 years, and claimed at least two victims — species of corals now marked “functionally extinct” from Florida’s reefs.

That finding comes from a newly published scientific paper that reads more like an obituary for two of the most visible and important coral species on Florida’s reefs: elkhorn and staghorn corals. In 2023, the ocean was warmer than it had ever been. When corals spend too long in hot water, they spit out the algae that live within their bodies, providing them food and shade.

…had been building reefs in Florida since the Ice Age. Since the Ice Age, elkhorn and staghorn corals off Florida’s southern coast have been stacking their skeletons into elaborate, branching homes for parrotfish, eels and octopuses. “They’ve been the most important reef builders on these reefs for 10,000 years,” said Ross Cunning, a coral biologist with Chicago’s Shedd Aquarium. But researchers are using stark, new language to describe the status of the two species in Florida: functionally extinct.“The numbers of individuals of these species that remain are now so low that they cannot perform their ecological functions in any meaningful way,” Cunning said. “This is the functional extinction of two incredibly important ecosystem engineers for coral reefs in Florida.” Cunning and a team of 46 other researchers published a grim study in the journal Science on Thursday that assesses the damage caused by a historic 2023 marine heat wave in Florida. The findings are essentially an announcement that the two coral species have disappeared there because of extreme ocean temperatures. The researchers determined that between 97.8% and 100% of these species’ colonies have died in the Florida Keys and near the Dry Tortugas islands. The findings came after divers from institutions across the state visited more than 52,000 coral colonies at nearly 400 sites.