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The 2014/15 El Niño – Part 14 – Warm Water Recirculated?

Bob Tisdale

There may still be a chance for an El Niño during the 2014/15 ENSO season. A new “pocket” of warm subsurface water has formed in the western equatorial Pacific. See the note in the page from the most-recent NOAA Weekly ENSO Update to the right. (Please click on illustration for full-sized image.) In their update, NOAA also makes note of that anomaly during their discussion of the Hovmoller on their page 15. That subsurface temperature anomaly appears to have been caused by the recirculation of warm water from the earlier downwelling (warm) Kevin wave, not by another westerly wind burst.  Come along, I’ll show you.

We’ve illustrated and discussed in recent posts the quickly diminishing remnants of the strong downwelling Kelvin wave that had carried a large pulse of warm water from the western equatorial Pacific eastward as far as South America. See…

…of this series. And the bottom line of those posts was, if the trade winds along the equatorial Pacific did not start to provide the feedback necessary to support an El Niño, the 2014/15 El Niño was going to die an early death…basically, it would run out of warm water.

Now a warm subsurface temperature anomaly has appeared in the west-central equatorial Pacific. See Figure 1, which is the most recent (a 5-day average centered on July 22) equatorial cross section available from the NOAA GODAS website. That pocket of warm subsurface water has been there, growing stronger, for the past few weeks.

Figure 1 – Equatorial Cross Section

Yet, according to the equatorial wind stress data, there has not been a westerly wind burst in the western equatorial Pacific for a few months to nudge any warm water from the West Pacific Warm Pool. See Figure 2. So where’d the warm water come from?

Figure 2 – Wind Stress Hovmoller

For that, we’ll have to look at an animation of the temperature anomaly maps for the top 300 meters of the oceans. But before we do, let me first show you what you’ll be looking for. See Figure 3. There is a pocket of warm water off the equator near the dateline. That pocket of warm water will be isolated as the equator cools. It travels slightly west and then gets “drawn” to the equator again.

Figure 3

And in Animation 1 you can watch that transpire. The animation starts with the May 3rd pentad (5-day average) and runs through July 22nd.

Animation 1

For those interested in watching the off-equatorial pocket of warm water form, see the animation here of sea level anomaly maps and temperature anomaly maps for the top 300 meters of the oceans from July Update. The “T300” maps are on the right. That animation runs from the start of the year to July 2, 2014, so it does not capture the warm water returning to the equator. That’s only happened over the past few weeks.

Animation 2 includes the equatorial cross sections for the same time period. Yes, there are other positive subsurface anomalies west of the one nearer to the dateline, so without the T300 maps, it’s difficult to speculate about how the larger warm anomaly formed.

Animation 2

BOTTOM LINE

Regardless of where that warm anomaly originated, it’s there now. The equatorial undercurrent in the Pacific (a.k.a the Cromwell Current) should now carry that anomaly to the east, where it should become a more-positive anomaly (because the water in the east is normally cooler than in the west). And if that additional warm water just south of the equator in the western tropical Pacific should also feed into the equatorial undercurrent, then there will be even more warm water to possibly fuel an El Niño for this year. (Yeah, I know, there’s lots of “shoulds” in those sentences, leading up to a “possibly”.)

We’ll just have to watch and see what Mother Nature decides to do. She’s always in control…and she’s always full of surprises.

EARLIER POSTS IN THIS SERIES

And for additional introductory discussions of El Niño processes see:

FURTHER READING

My ebook Who Turned on the Heat? goes into a tremendous amount of detail to explain El Niño and La Niña processes and the long-term aftereffects of strong El Niño events. Who Turned on the Heat? weighs in at a whopping 550+ pages, about 110,000+ words. It contains somewhere in the neighborhood of 380 color illustrations. In pdf form, it’s about 23MB. It includes links to more than a dozen animations, which allow the reader to view ENSO processes and the interactions between variables.

I’ve lowered the price of Who Turned on the Heat? from U.S.$8.00 to U.S.$5.00. A free preview in pdf format is here. The preview includes the Table of Contents, the Introduction, the first half of section 1 (which was provided complete in the post here), a discussion of the cover, and the Closing. Take a run through the Table of Contents. It is a very-detailed and well-illustrated book—using data from the real world, not models of a virtual world. Who Turned on the Heat? is only available in pdf format…and will only be available in that format. Click here to purchase a copy. Thanks. (I also am very happy to receive tips or donations.)

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