After the Blob dissipated, researchers learned that the effects of a severe marine heat wave could endure long after the event itself has passed.
Ted Cheeseman, a Ph.D. candidate at Southern Cross University, had co-founded Happywhale, a database of tens of thousands of marine mammals built on photos submitted by researchers and whale watchers around the world. Mr. Cheeseman found a sharp drop in humpback whale sightings by 2021.
The decrease was so significant, at first he thought the Happywhale team was doing the math wrong. They spent several years checking, and last year published a study that concluded the humpback whale population in the North Pacific had fallen by 20 percent from 2012 to 2021. They attributed the decline to the loss of food like krill during and after the Blob.
With “an estimate of 7,000 whales having disappeared and not showing up anywhere else,” Mr. Cheeseman said, “there’s really no other explanation.”
Looking Ahead
Eventually, parts of the ocean might enter a constant state of marine heat wave, at least by today’s common definition. Some scientists see today’s shorter-term spikes as practice for this future.
Alistair Hobday, a biological oceanographer at Australia’s Commonwealth Scientific and Industrial Research Organisation, has been conducting public briefings with marine heat wave forecasts months ahead of time.
People are tuning in — and responding.
The critically endangered red handfish lives off the coast of Tasmania, crawling along the seafloor on fins shaped like hands. These unusual fish have only been found within two small patches of rocky reef and sea grass meadow.
In late 2023, Dr. Hobday’s forecast predicted potentially deadly marine heat waves. Researchers from the University of Tasmania’s Institute for Marine and Antarctic Studies, with support from the Australian Department of Climate Change, took a drastic step. They transferred 25 red handfish to an aquarium until the temperatures fell.
Jemina Stuart-Smith, an ecologist at the University of Tasmania, described those weeks as the most stressful time of her life. “If it all went wrong,” she said, “you’re talking about the potential extinction of an entire species.”