How 'The Blob' may prolong El Nino

05 Nov, 2015 04:35 AM
The huge "blob" of abnormally warm water extends from the Californian coast far into the Pacific.

THE powerful "Great Godzilla" El Nino in the Pacific may last as much as two months longer than expected because of another unusual climate phenomenon scientists have nick-named "The Blob".

First observed in 2013, the huge "blob" of abnormally warm water extends from the Californian coast far into the Pacific.

One effect is that the winds that blow westward during an El Nino are much further north than they would normally be at this time in the event's cycle, researchers in the US and Australia say.

This year's El Nino already ranks among the most powerful in history. Its impacts range from bushfires blanketing Indonesia in smoke, droughts in Papua New Guinea and heatwaves across southern Australia, to floods in the Americas as winds and rainfall patterns shift.

"The funny thing with this El Nino is the same wind anomaly that we would have expected on the Equator is sitting north of the equator," Axel Timmermann, a professor of oceanography at the University of Hawaii told Fairfax Media.

"The north Pacific is so much warmer than the south Pacific, and typically around this time or a month from now, the wind anomalies should already have moved to the south [of the Equator]."

Those westward winds are currently blowing about 5-7 degrees north of the Equator, with southerly surges flows from near Australia providing some of their power.

Wenju Cai, a principal research scientist with the CSIRO who has published widely on how climate change will likely make extreme El Ninos more common, said the timing of these winds is particularly unusual and will likely prolong the event.

"This pattern is often one of the features of an extreme event but I didn't expect it to last until now," Dr Cai said.

"This pattern is good for charging the heat in the Pacific," he said. "It's going to make the battery last longer, that's for sure."

Mike McPhaden, a senior NOAA scientist, said the current El Nino is "the strongest in a generation and it continues to grow in its amplitude".

As the Bureau of Meteorology chart below shows, recent westerly wind bursts have triggered a further rise in abnormally warm temperates in a key region of the Pacific.

The 2.3-degree anomaly is still shy of the record 2.8 degrees recorded in 1997-98, but it is predicted to rise further before the event peaks late this year, the bureau said.

Dr McPhaden cautioned that the El Nino's demise is hard to predict five to six months out, noting the 1997-98 event broke down within a matter of weeks in May 1998.

The Blob, though, had made this El Nino particularly unusual because it had abnormal differences in temperatures between the north and south Pacific.

"How this will affect what's happening on the Equator is a very interesting question," Dr McPhaden said.

"I'm not sure we understand that yet," he said. "It's quite possible it could lead to some prolongation of the event."

La Nina switch

The extreme weather events associated with this El Nino are already straining the resources in countries such as Papua New Guinea or cyclone-hit Vanuatu in the Pacific.

Any extension would likely add to the misery and stretch economies and ecosystems further.

Dr Cai said the El Nino, based on US definitions, could last until May, June or even July.

Professor Timmermann said University of Hawaii's own seasonal forecasting models show "there is some indication this El Nino will last two months longer on average than the 1997 event".

Since El Ninos tend to flip into La Ninas - when Pacific trade winds revert back to be easterlies but intensify - many nations could be in for extreme conditions the other way.

China, for instance, may shift within a few months from excessively dry to abnormally wet weather.

"This is a recipe for big floods in China: a huge El Nino which drives dry conditions and then a switch to a La Nina," Dr Cai said.

"The longer it lasts, if it is to switch into a La Nina, the faster it has to do it," he said.

While El Nino years generally have relatively few tropical cyclones making landfall in Australia but La Nina years typically have more such super storms than usual.



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