PACIFIC island countries may face different consequences from the same El Niño pattern, with warmer water, changing sea levels, coral stress and shifting tuna grounds expected across the region, SPC Ocean Science Officer Dr Moleni Tu’uholoaki said.
“El Niño is closely similar to 1982/83, 1997/98 and 2015/6,” Tu’uholoaki said, referring to earlier events. But he warned against assuming that a familiar pattern would produce the same outcome in every country.
“The impact of El Nino is not the same,” he said. “If you look at a pattern, it is the same … but they are different” in strength and local effect.
Warm water in the central and eastern Pacific is linked to higher sea levels in those areas, while sea levels are lower in the western Pacific, Tu’uholoaki said.
“Whenever El Nino is still there, so the Western Pacific is lower and the eastern Pacific is high,” he said, adding that the national-level impact could still vary.
For low-lying Pacific communities, the shift can expose waves and coral reefs for longer periods. Prolonged exposure can place stress on coral, with the effects linked to changes in sea level.
The ocean changes are also expected to affect fisheries, particularly tuna. Tu’uholoaki said fish cluster around temperature lines that move over time, changing the location of fishing grounds.
“The big one, a fish will cluster around this line,” he said. “It shifts in time.” Temperature patterns can show “where it is likely to have this kind of tuna.”
The change does not necessarily mean tuna will disappear from the Pacific, but that fishing grounds may move.
“It hasn’t been tuna somewhere, just shifting your fishing ground, you just shift,” Tu’uholoaki said.
The 2015-16 period offers a recent example of the risks. Warm water in the central Pacific was linked to coral bleaching, particularly in Kiribati, while Fiji experienced coral stress in February 2016.
Tu’uholoaki described that period as involving “mass and widespread mortality”. Marine heat conditions were classified as “moderate, strong, severe and extreme”.
The outlook for September through December shows a pattern similar to historical conditions, with the central and eastern Pacific remaining important for tuna movement and warmer water focused on the equatorial region.
But history does not guarantee the next local outcome.
“It might be different this time; nobody knows, but this is history,” Tu’uholoaki said.
Past comparisons also point to higher-than-average tropical cyclone activity during El Niño. The figures cited included 18 cyclones in one period, 20 in another and 24 in 2015-16, while the timing of future activity remained uncertain.
“Coming down to the national level, it’s different.”
