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The Northeast Pacific ocean, off the U.S. West Coast, is experiencing its fourth-largest marine heat wave since record-keeping began in 1982.
“The extent of the current Pacific marine heatwave should be surprising … but unfortunately, record breaking heat is our new norm,” Chris Free, a marine scientist at the University of California, Santa Barbara, told Mongabay.
Large marine heat waves have become a recurring theme in the Northeast Pacific since the early 2010s. In 2013, the region was gripped by what was nicknamed The Blob, a massive marine heat wave that stretched from the Gulf of Alaska to Southern California. Lasting roughly three years, The Blob had catastrophic impacts on marine wildlife and ecosystems in the region and was followed by more devastating heat waves.
The current Blob, officially NEP25A, first emerged in early May within the Gulf of Alaska and rapidly expanded to cover an area of about 8 million square kilometers (3.1 million square miles), roughly the size of the contiguous U.S., according to researchers with NOAA Fisheries’ California Current Integrated Ecosystem Assessment (IEA).
“NEP25A gained much of its size when a low-pressure system crossing the Gulf of Alaska reversed coastal winds that had helped cool the ocean surface. The heatwave grew and approached the West Coast approximately one month ahead of other large heatwaves in recent years,” NOAA IEA notes.
NEP25A is part of a much larger ongoing marine heat wave system stretching across the North Pacific, from the waters off Japan to North America’s west coast.
Several recent studies attribute the rising marine heat waves in the Northeast and North Pacific to climate change.
“Five of the six largest marine heat waves in the Northeast Pacific have all occurred in the last six years,” Free said. “This trend in record breaking heat is alarming because of its impacts on ocean ecosystems and economies.”
The 2013-2016 Northeast Pacific heat wave, for instance, led to the collapse of kelp forests, mass deaths of seabirds and sea lions washing ashore, harmful algal blooms, and the disruption of entire marine food webs. Fisheries like those of the Pacific sardine also suffered, Free said.
The current blob, NEP25A, has also “been accompanied by reports of warmer-water species such as marlin and tuna to the north of their typical range, and signs of harmful algal blooms that can be fueled by warmer waters along the Oregon Coast,” NOAA Fisheries said in a statement to Mongabay. “If the marine heatwave grows and persists, it may further affect the large California Current Ecosystem through shifts in marine life and changes in the food web, for instance.”
However, “NOAA’s latest forecasts predict that marine heatwave conditions will ease near the West Coast as we move into winter, though they are likely to persist farther offshore,” the statement added.
