IT’S not every day that a scientific paper refers to a John Steinbeck novel. But one study published this week does just that, citing Cannery Row, the American author’s chronicle of a Californian fish-canning community.
Why? Because Steinbeck’s novel, which depicts the sardine glut of the 1940s, turns out to be a salient text in a radical new interpretation of the workings of the world’s climate.
Researchers have uncovered the importance and influence of an ocean cycle that dominates the Pacific every 25 years or so, a discovery that threatens to fundamentally change our understanding of El Niño, global warming and the mysterious fluctuations in world fish stocks.
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Francisco Chavez,whose workplace at the Monterey Bay Aquarium Research Institute is just round the bay from the real Cannery Row, believes the ocean circulation pattern he uncovered is the mysterious “Pacific decadal oscillation” pattern, the presence and effects of which marine scientists have been debating for years. Oceanographers contacted by 91av mostly agree.
In Steinbeck’s day, Californian sardines were the US’s biggest fishery. And catches in Peru, Chile and Japan were not far behind. Then around 1950, they collapsed. Peruvian anchovies became the largest single-species fishery in the world until they too crashed in the mid-1970s – and the sardines returned in force. Only in the past five years have anchovies staged a comeback, while sardine catches have crashed by up to 99 per cent.
Until now, marine biologists have blamed overfishing for these dramatic crashes. But deeper forces are at work, says Chavez. He sees the Pacific’s sardines and anchovies as its yin and yang. When the waters are running with one, the other “practically disappears”. The switch happens roughly every 25 years. To find out why, Chavez checked out a raft of data on historical conditions in the Pacific. He checked air and ocean temperatures and atmospheric carbon dioxide levels, alongside sardine and anchovy numbers.
During the “sardine regime”, Chavez found that the Pacific waters are warm and El Niños are strong. During the “anchovy regime”, the waters are cool and El Niños are muted (Science, vol 299, p 217). Right on cue, the current El Niño, first of the new “anchovy” regime, is much less intense than the last of the old regime. These synchronous changes have persisted for at least a century, Chavez says. Similar, but inverted, cycles occur off southern Africa.
More dramatic still, the air temperature of the whole planet generally rises when sardines are swimming the Pacific. Does that mean that the planet will start to cool now the anchovies are re-emerging? Chavez doubts it. He thinks the current greenhouse effect will prove too strong and mask any cooling.
So far, the new cool phase in the Pacific has not obviously dented world temperatures. Last year was the second-warmest year on record, beaten only by 1998. But Chavez does believe that at least part of the global warming of the past quarter-century could be down to Pacific cycles, and warming in the next quarter-century could be more muted.
So what is causing this strange ocean phenomenon? One clue is that during “sardine regimes”, the whole ocean begins to resemble an El Niño event. Warm surface water spreads, suppressing deep-water currents that bring cold nutrient-rich water to the surface off the Americas. This triggers new patterns of ocean currents and weather systems across the entire ocean. That means fewer plankton, fewer anchovies and fewer sea birds. And, for reasons not wholly explained, sardines thrive from Japan to the Americas. Meanwhile the ocean’s “anchovy regime” resembles the conditions during La Niña. In both regimes, the warming and cooling of such a large area of ocean have a knock-on effect on average global temperatures. “Fish in many parts of the Pacific are marching to the same drum,” Chavez says.
Where does the drumbeat come from? Frank Schwing of the Pacific Fisheries Environmental Laboratory in Pacific Grove, California says the answer may lie in the slow rhythms of the deep ocean, about which we know little. He speculates that global warming could spark a “perpetual ‘sardine regime’, or something even less welcome.”
