The northeast Pacific’s largest marine heatwave on record was at least partially caused by El Niño climate patterns. And unusually warm water events in that ocean could potentially become more frequent with rising levels of greenhouse gases.
Those are the findings of a study by researchers from Georgia Tech and the National Oceanic and Atmospheric Administration. They linked the 2014- 2015 marine heatwave — often referred to as the “warm blob” — to weather patterns that started in late 2013. The heatwave caused marine animals to stray far outside of their normal habitats, disrupting ecosystems and leading to massive die-offs of seabirds, whales, and sea lions.
“We had two and a half years of consistent warming, which translated to a record harmful algal bloom in 2015 and prolonged stress on the ecosystem,” said Emanuele Di Lorenzo, a professor in Georgia Tech’s School of Earth and Atmospheric Sciences. “What we do in the study is ask whether this type of activity is going to become more frequent with greenhouse gases rising.”
The researchers traced the origin of the marine heatwave to a few months during late 2013 and early 2014, when a ridge of high pressure weakened winds that normally bring cold Arctic air over the north Pacific. That allowed ocean temperatures to rise a few degrees above average.
Then, in mid-2014, the tropical weather pattern El Niño intensified the warming throughout the Pacific. The warm temperatures lingered through the end of the year, and by 2015, the region of warm water had expanded to the West Coast, where algal blooms closed fisheries for clams and Dungeness crab.
The study, sponsored by the National Science Foundation, was published in the journal Nature Climate Change. — Josh Brown