The Arctic is already warming up at twice the rate of the rest of the planet. Now researchers have warned that a little-known natural cycle in the Pacific is entering a phase that could make it heat up even faster.
The rapid warming of the Arctic is already causing havoc, causing seasonal sea-ice cover around the Arctic Circle to retreat by record amounts and making life tough for animals such as polar bears. The warming is also disrupting weather patterns, and could be a key factor behind the ongoing heatwave devastating countries throughout the northern hemisphere.
A bit like El Nino, the Pacific Decadal Oscillation (PDO) is cyclical, switching from warm to cold phases every 20 years or so. Phases of the PDO are dictated by Pacific sea surface temperatures. The warm phase sees higher temperatures in the tropical Pacific and along the western coastline of America, with colder temperatures in the north. The pattern reverses in the cold phase.
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The upshot is that as the warm phase kicks in, it could amplify warming in the Arctic that’s already twice the rate elsewhere on the planet. “It’s possible it will warm the Arctic even more,” says Lea Svendsen of the University of Bergen in Norway, and head of the team investigating the effect of the PDO. “But we need to wait at least another 10 years or so to find out.”
“If this mechanism holds up, we would expect higher temperatures and potentially more ice melt related to the Pacific,” says Ruth Mottram of the Danish Meteorological Institute in Copenhagen. “But it’s only one model in this study and it’s probably necessary to replicate with other models to be sure of the connection,” she says, adding that the Pacific is under-studied compared with the Atlantic influence on global warming.
In other research, Jennifer Francis and her colleagues at Rutgers University in New Jersey linked increased Arctic warming to the cold phase of the PDO, but she says the effects found by Svendsen might be different because of the increased ice cover a century ago. “One thing that’s clear to me is that extra heat entering the Arctic—no matter where it comes from—is intensified by the many self-amplifying feedbacks that operate there,” says Francis.
