This year brought one of the biggest marine heat waves on record in the Pacific Ocean, and it’s one of several record-setting spikes in ocean water temperatures over the last six years.
The string of warm water events has scientists wondering if this is actually the new normal for the Pacific Ocean.
A series of heat waves started in 2013 with what was nicknamed “the blob,” which brought water temperatures up to nearly 7 degrees Fahrenheit higher than normal across a 1,000-mile stretch of the West Coast.
The warm water caused massive harmful algae blooms that shut down crab and clam fisheries and affected food availability for wildlife. Many young sea lions were left stranded on beaches by parents searching for food. Whales started feeding closer to shore, which caused more of them to be struck by vessels and entangled in fishing gear. The heat wave also brought warm-water species farther north and spurred a baffling proliferation of a pickle-shaped creature known as a pyrosome.
Andrew Leising, a scientist with the National Oceanic and Atmospheric Administration, uses satellite data to track how much of the ocean is much warmer than normal in these heat waves.
“For the last six years, we’ve now had the three largest events on record,” he said. “It’s tempting to say, ‘OK, this may be the new normal.”
However, Leising said, satellite data only goes back to 1982. So, this could be part of a temperature cycle that hasn’t been documented before.
“My take on it is it’s just still too early to say,” he said. “We need another couple years of data and more research into the pressures and drivers of what’s causing them to really understand if we’re in a new pattern.”
The ocean is also getting warmer with climate change, which complicates the measurements scientists use to identify a marine heat wave. Leising said the definition of a heatwave might need to change as the overall temperature of the ocean rises.
“Basically, in 40-50 years from now, everything will look like a heat wave if we keep the same definition we have now,” Leising said. “The whole ocean will be a heat wave all the time, right? But that’s kind of meaningless.”
It is important to distinguish between long-term warming and shorter-term temperature spikes because they can have different effects on the marine ecosystem, he said.
“The heat waves are basically exacerbating the effects of background warming,” Leising said. “And that actually can be important for some animals because certain fish and other animals have these absolute limits. ... suddenly it gets to 25 degrees Celsius and bam, it’s dead. They do fine up until a certain point and then they just can’t have it any warmer.”
Research shows warmer water and more frequent marine heat waves are increasing the risks of harmful algal blooms in the ocean.
A recent study found the 2013-2015 marine heat wave created a new toxic hot spot near the border of Oregon and California where the algae that produce domoic acid have shut down fisheries every year since the heat wave and are likely to continue proliferating in that area in the future.
Fishery managers are developing new systems of forecasting harmful algal blooms that produce domoic acid, a potentially deadly neurotoxin, so they can provide early earnings and prevent people from eating shellfish that could poison them.