Has The Pacific Blob Delayed La Niña?

  • Date: 13/09/16
  • David Whitehouse, Science Editor

The Pacific Blob’s contribution to the record global temperatures is significant. Is it also delaying the La Niña?

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In most of the discussions about the factors behind the record-breaking global temperature of 2015 and probably 2016, the crucial contribution made by an intense El Niño is often mentioned, though not as often as it should be. Mentioned even less is the so-called Pacific “blob.” According to researchers writing in the journal Nature, “Between the winters of 2013/14 and 2014/15 during the strong North American drought, the northeast Pacific experienced the largest maritime heatwave ever recorded.” The blob’s contribution to the record global temperatures is significant.

It formed in the Gulf of Alaska during the autumn of 2013. The following year it had spread across the North Pacific to the Oyashio, Sea of Okhotsk, the Bering Sea, and to the waters offshore of the California Current. In February and June of 2014, the Gulf of Alaska had temperature anomalies of +2 to +4°C to depths of 100 m; the western North Pacific warmed an equal amount during the summer of 2014. During that summer its effects began to diminish, but it remained a prominent feature in the Northeast Pacific. In mid-September northerly winds ceased and the blob moved into the shelf waters off southern British Columbia, Washington and Oregon, raising coastal sea surface temperatures by 6°C. In November of 2014, it was entrenched in coastal waters off Oregon. The blob continued throughout the summer and autumn of 2015.

By December of 2015 many considered the blob had dissipated; By then the El Niño was intense. But the latest measurements indicate that the blob has not gone away and is currently resting several hundred metres below the ocean’s surface. The new data indicates that the region’s upper waters are being mixed by the wind again and coming back to normal temperatures, but the residual effect of the blob is still there at about 150 to 200 metres below the surface.

The reason why the blob was declared dead at the end of 2015 was that satellite thermal images no longer detected abnormally warm waters on the surface of the Pacific Coast. However, the imaging only reached up to 40 metres below the surface. The most recent vertical measurements suggest that the blob might be starting to weaken at the new depth.

Delayed La Niña

Many scientists expected that in the next few months a La Niña – an ocean-atmospheric system that has a cooling effect on surface temperatures – would bring temperatures back to normal. When the expected region of cold water started to breach the surface last May, ending the El Niño’s reign, climatologists forecasted a 75 percent chance La Niña would be here by the end of the year. But recently NOAA’s Climate Prediction Center changed its mind and is now predicting neutral conditions persisting through the forthcoming winter. The probability of a La Niña has been downgraded significantly to about 40 percent.

The delayed La Niña will obviously affect global temperatures keeping the globe warmer for longer. Despite the ending of the El Niño and subsequent cooling 2016 was already on course to be a record because of the strength of the El Niño’s contribution.

NOAA’s next updated long range 30- and 90-day forecasts, are due out on September 22nd. It will be fascinating to see if the blob is a factor in predictions and its interaction with the missing La Niña.

Feedback: david.whitehouse@thegwpf.com

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