- Researchers noticed sharks moving farther north during a marine heat wave.
- The trend has continued.
- Scientists say global warming fuels extreme ocean temperature changes.
Young great white sharks have been showing up over the past few years in parts of California’s Monterey Bay where they had never been spotted before.
New research says that’s because warming ocean waters have led them to expand their habitat farther north.
“These sharks – by venturing into territory where they have not historically been found – are telling us how the ocean is being affected by climate change,” Monterey Bay Aquarium Chief Scientist Kyle Van Houtan, one of the study’s authors, said in a news release.
(MORE: Lizards May Be Why Lyme Disease Is Rare in the South and More Common in the Northeast, Study Says)
In the study published Tuesday in the journal Scientific Reports, Van Houtan and his colleagues analyzed data from electronic tags on juvenile great whites, also known simply as white sharks. Researchers began tagging the sharks in Southern California waters in 2002 to learn more about the species.
A marine heat wave known as “the blob” hit the West Coast between 2014 and 2016, extending from the Gulf of Alaska to Baja California in Mexico. Sea surface temperatures rose as much as 7 degrees Fahrenheit in some areas, according to NOAA.
The blob affected marine life from krill to whales and was blamed for a record outbreak of toxic algae.
At the same time, shark researchers noted sightings of juvenile white sharks in the waters just off the Central California community of Aptos. It was the farthest north the sharks had ever been seen.
Unusually high water temperatures have become more common in the Aptos area since the blob, and the great white shark sightings have continued ever since, according to the study.
The blob and other marine heat waves have been extensively researched. Many atmospheric and weather conditions contribute to the formation of marine heat waves, but scientists say warmer ocean waters tied to global warming help fuel such extreme ocean temperature changes.
“We know a lot of extra heat from the atmosphere due to increased greenhouse gas concentrations has gone into the ocean,” Washington State Climatologist Nick Bond said in a 2019 NOAA paper. “So when we’ve gotten unusual weather patterns due to natural variability, they’ve caused fluctuations in ocean temperatures that are on top of that global warming. That means when we had a big fluctuation — like the blob of 2014-16 — that was expressed on top of that upward trend. It meant that the temperatures were that much warmer as a result.”
A study published in September in the journal Science found climate change was causing more frequent extreme heat waves.
Warmer temperatures on both land and in the oceans are driven by greenhouse gas emissions that trap heat. Most of the excess heat is absorbed by oceans, according to NOAA.
Besides marine heat waves, rising ocean heat content is also contributing to sea level rise, coral bleaching and the melting of glaciers and ice sheets.
The California shark study is just one piece of those effects.
“I think this is what many biologists have expected to see as the result of climate change and rising ocean temperatures,” Chris Lowe, a co-author of the study and director of the Shark Lab at California State University, Long Beach, said in the news release. “Frankly, I’ll be surprised if we don’t see this northerly shift across more species.”
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
Credit: Source link