In this Sept. 14, 2017, file photo, salmon circle just below the surface inside a lock where they joined boats heading from salt water Shilshole Bay into fresh water Salmon Bay at the Ballard Locks in Seattle. Federal scientists say they're monitoring a new ocean heat wave off the West Coast. Researchers with the National Oceanic and Atmospheric Administration said Thursday, Sept. 5, 2019, the expanse of unusually warm water stretches from Alaska to California, and it resembles a similar heatwave that disrupted marine life five years ago. It remains to be seen whether this heat wave will linger or dissipate more quickly than the last one. (AP Photo/Elaine Thompson, File)

Federal scientists said Thursday they are monitoring a new ocean heat wave off the U.S. West Coast, a development that could badly disrupt marine life including salmon, whales and sea lions.

The expanse of unusually warm water stretches from Alaska to California, researchers with the National Oceanic and Atmospheric Administration said Thursday . It resembles a similar heat wave about five years ago that was blamed for poorer survival rates for young salmon, more humpback whales becoming entangled in fishing gear as they hunted closer to shore, and an algae bloom that shut down crabbing and clamming.

"Given the magnitude of what we saw last time, we want to know if this evolves on a similar path," said Chris Harvey, a research scientist at the Northwest Fisheries Science Center.

NOAA Fisheries said the water has reached temperatures more than 5 degrees Fahrenheit above average. It remains to be seen whether this heat wave dissipates more quickly than the last one, the agency said.

Scientists dubbed the last West Coast heat wave "the blob."

The new heave has emerged over the last few months, growing in a similar pattern in the same area. It's the second-most widespread heatwave in the northern Pacific Ocean in the last 40 years, after "the blob."

In this Sept. 14, 2017, file photo, brothers Judah, left, and Harrison Ellis watch salmon swim past viewing windows at a fish ladder where salt water transitions to fresh at the Ballard Locks in Seattle. Federal scientists say they're monitoring a new ocean heat wave off the West Coast. Researchers with the National Oceanic and Atmospheric Administration said Thursday, Sept. 5, 2019, the expanse of unusually warm water stretches from Alaska to California, and it resembles a similar heatwave that disrupted marine life five years ago. It remains to be seen whether this heat wave will linger or dissipate more quickly than the last one. (AP Photo/Elaine Thompson, File)

"It's on a trajectory to be as strong as the prior event," said Andrew Leising, a research scientist at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, California, who developed a way to use satellite data to track marine heatwaves in the Pacific.

The agency said it will provide fisheries managers with information on how the unusually warm conditions could affect the marine ecosystem and fish stocks.

The last heatwave spanned 2014 and 2015 and resulted in several declared fisheries disasters. Among the other effects, thousands of young sea lions were stranded on beaches after their mothers were forced to forage further from their rookeries in the Channel Islands off Southern California.

Explore further West Coast waters returning to normal but salmon catches lagging

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