Giant blob of cold water rises from the depths of the Pacific, possibly heralding the arrival of La Ni単a this fall

By Tom Yulsman | September 23, 2017 12:21 pm
La Ni単a

This animation shows how temperatures at the surface and subsurface of the tropical Pacific ocean departed from average over five-day periods starting in early August 2017. The vertical axis shows the depth below the surface in meters. The cross-section is right along the equator. Note the blue blob indicative of relatively cool water rising from the depths and spreading eastward. (Source: NOAA ENSO Blog)

Here we go again?

Followinga mild and short-lived La Ni単a episode in 2016/2017, the climatic phenomenon stands a 55 to 60 percent chance of developing once again this fall and winter. That’sthe most recent forecast from the National Oceanic and Atmospheric Administration.

Based on observations of what’s happening in the Pacific Ocean, and modeling topredict what may be coming, NOAA’s Climate Prediction Center has issued a La Ni単a watch, indicating that conditions are favorable forits development.

La Ni単acan strongly shift weather patterns,bringinganomalously cool or warm, and wet or dry, conditions tolarge parts of the world. In the United States, La Ni単a tends to bring wetter than normal conditions to the Pacific Northwest and parts of the Midwest.Unfortunately for southern and central California, things tend to dry out.

When a blob of cool water in the Pacific depths leads to La Ni単a, these are the typical impacts on North America.

Here’s how La Ni単a tends to influence weather patterns across North America. (Source: NOAA)

But it’s important to note that with La Ni単a (or its opposite, El Ni単o, for that matter), YMV. For example, last winter, despite the presence of La Ni単a,incredibly heavy precipitationdrenched large parts of California. This was thanks to another phenomenon, known as the “pineapple express“.

A number of factors have climatologists convinced that La Ni単a is brewing again. Among them are changes to Pacific Ocean trade winds.

These ordinarily blow from east to west across the equatorial Pacific, helping to bottle up warm surface waters in the western part of the ocean basin. As a La Ni単a episode gets going, those winds tend to strengthen,shoving even harder on warm surface waters, pushing them out of the way, and thereby allowing cooler water to well up from the ocean depths.

This is precisely what began to happen during August. At about 160to 500 feetbeneath the surface of the Pacific, a blob ofcooler-than-average waterformed and began rising and spreading to the east along the equator.

You can see this blob, called a “kelvin wave,” in the animation at the top of this story. The visualization depicts a cross-section of the Pacific Ocean along the equator, and it shows the evolution of the cold blob starting in early August.

This shift in conditions in the Pacific had its origins even prior to August. “During the second half of July, the trade winds puffed a bit harder over the western half of the Pacific, likely helping this current Kelvin wave form,” writes Emily Becker in NOAA’s informative and compellingly clear ENSO Blog.

Parts of the blob reached the surfacein August, resulting in anomalously cool surface waters along the equator. This ischaracteristic of La Ni単a. But it’s important to note that this and other features have to strengthen and persist before NOAA will declare the official start of a La Ni単a episode.

La Ni単a

This animation compares sea surface temperature anomalies in the Pacific Ocean on May 12 and Sept. 12, 2017. The blue swath thatforms along the equator indicates cooler than normal temperatures that have developed since May. (Images: Earth Nullschool. Animation: Tom Yulsman)

In the animation above, watch the equatorial region of the Pacific west of South America. The colors indicate how temperatures at the sea surface vary from the long-term average.The warmish hues along the equator in one of the two frames are indicative of slightly warmer than normal temperatures at the surface in mid-May of this year.

In that same frame, orange and yellow tones hugging the west coast of South America reveal particularly warm water evidence of a “coastal El Ni単o.” This phenomenon sometimes is a prelude to a full-fledged El Ni単o, in which a spear of unusually warm waterextendswestward from the coast of South America along the equator.

But as the second frame in the animation shows, that’s not what happened this time.That second frame shows sea surface temperature anomalies in mid-September. And the spear of blue along the equator indicates acool-down.

Will conditions continue along this path, resulting in a La Ni単a? That’s the forecast of computer models. As Emily Becker writes at the ENSO blog:

The ensemble of models from theNorth American Multi-Model Ensemble (NMME)is predicting that La Ni単a will develop this fall, and last just through the winter. Back-to-back La Ni単a winters are not uncommon, and have occurred at leastfive times since 1950, most recently in 2010-2011 and 2011-2012.

There are good scientific reasons to feel confident in the model predictions. But as Becker is quick to point out, the interactions between the ocean and atmosphere are very complex. So things may very well evolve differently.

One thing is for sure, of course: Time will tell.

CATEGORIZED UNDER: Climate, ENSO, Ocean, select, Top Posts
  • OWilson

    “the interactions between the ocean and atmosphere are very complex. So things may very well evolve differently” (from the models).

    Well said!

    There are reports that the glaciers are growing in Greenland, New Zealand, the Himalayas (K2) and even here in the U.S. (Glacier National Park)

    Mother Nature refuses to be constrained to “models”!

    • TLongmire

      Perhaps an extradementional being coded our matrix to confound us once again

    • Tom Yulsman

      One year does not make a trend. It is just one data point. And the trend in Greenland is quite clear: Over the long term, it has been losing ice. And not just a little. From the Polar Portal, produced by Danish Arctic research institutions ( ):

      “Since at least 2002, the total mass budget has been substantially negative (on average from 2002 onwards it has lost -200 to -300 Gt per year). This year, thanks partly to ex-hurricane Nicoles snow and partly to the relatively low amounts of melt in the summer, we estimate the total mass budget to be close to zero and possibly even positive. Greenland on average loses around 500 Gt of ice each year from calving and submarine melt processes. If we subtract this from our figure of 544 Gt for the SMB it would suggest Greenland gained a small amount of ice this year. However, compared to the approximately 3600 Gt of ice, corresponding to 1cm of global average sea level rise that Greenland has lost since 2002 this years slightly positive balance does not add much extra.”

      And now I will anticipate your reply something like this: “1 cm of sea level rise? Trivial.” Of course that would ignore that this increase is just since 2002. It would also ignore how much Greenland can contribute over time, especially as the climate warms more and melting speeds up.

      Natural variation could take us into a cooling period for a time. And yes, maybe there is something fundamental scientists don’t understand about the climate system. You’ve placed your bets on that. But I have more faith in science than you apparently do. And in one way, I may be more conservative than you are: I believe that when it comes to planetary life support systems, the precautionary principle should guide our actions.

      • Robert E. Lee

        You missed one thing . You can’t do nothing to stop or change this . It is imminent like it was millions of years ago . No need to impose new taxes on people because you , “science believers” and miserable globalists , just want this .

      • OWilson

        “And now I will anticipate your reply something like this: “1 cm of sea level rise? Trivial.”

        You should know me by now.

        I certainly know you folks!

        I’m only interested in current raw data from original and official research sites, like NSIDC, NASA, DMI, and NOAA.

        I’m not at all interested how the Washington Post, Wood for trees, or your Porta-Portals “organize” and “present” that information.

        A quck check of your cite source, reveals a climate and energy advocacy site that aggregates and “reports on” officilal sources!

        You guys are SO predictable! :)

      • Cjones1

        I am glad you speak of trends because the AGW proponents have trended towards ignoring the history of climate change. Accurate measure of temperature and other metrics have only been around for less than 200 years or so…in few locations as the science expanded. Core data from a variety of locations has expanded our understanding of climate history, but many chapters of the book have yet to be translated.
        Solar sunspot cycle data reports a continuing downwards trend similar to Cycle #5 which preceded the Maunder Minimum and Little Ice Age. It is said that by late 2019 the descent into a colder climate will become to obvious to ignore.
        Be prepared to throw another log on the fire!

      • salrol

        Greenland is perfect to discuss!
        You know that inland ice move mostly because of its weight. In Greenland the ice is placed in a gigant basin surrounded by nanutakks. Here and there icefloods move through the nanutakks. The ice is also upp to 1800 m over sea-level and the basin up to 1800 m under sea-level. The ice grows when it snows more than it melts away which means the mass grows which means the icefloods will increace its speed. Then there is a lot of ice calvings.
        But if warmings melt away more snow than is falling, then the wheight of ice will reduce slightly every year and the speed of ice floods will reduce and produce less calvings.
        Of course the process is more complex than descibed above.

        So, when it is reported increace of calvings the inland ices should be increacing too, not the oposite.

    • E L


  • Russ

    So, where does the cooler water that defines a la nina come from? From melting of the ice floes in the Antartica?

    • E L





ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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