A chinook salmon near Umatilla, Oregon. Changes to Pacific ecosystems may be due to sea temperature fluctuation, a new paper says. (Photo by Jeff T. Green/Getty Images)

Two “rapid and widespread” changes in the ecosystem of the North Pacific have puzzled scientists for decades.

But now, a new paper holds that climate fluctuations — longer and less frequent than perhaps once believed — are behind this scientific mystery.

In both 1977 and 1989, salmon and plankton populations in some North Pacific areas dropped dramatically, while increasing in other areas. Chris Boulton and Tim Lenton of the University of Exeter say this is because of longer, less frequent sea temperature changes in the region, dubbed regime shifts.

“The causes of these dramatic ecosystem shifts in 1977 and 1989 have been a scientific mystery,” Boulton said in a . “This is the first time that anyone has looked for changes in sea surface temperature fluctuations in the North Pacific, and we have now gone some way towards explaining what causes these regime shifts, which have extreme consequences for aquatic life.”

The findings may have future implications for marine life. By monitoring sea surface temperature changes, scientists could have “early warning of threats to marine ecosystems,” Lenton added, according to the press release.

In some areas of the world, sea surface temperature has increased by as much as 4 degrees Fahrenheit since 1900, according to data from the . That's a rate of 0.13 degrees per decade. During the past 30 years, recorded sea temperature has been higher than in any other time since reliable observation began in 1880, on its website.

, “Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change,” was published in the Proceedings of the National Academy of Sciences on Aug. 31.

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