Stronger Winds Shift Heat to Deeper Pacific

February 11, 2014

Dana Nuccitelli in the Guardian:

While the rate of surface temperature warming has slowed in recent years, several studies have shown that the warming of the planet as a whole has not.  This suggests that the slowed surface warming is not due as much to external factors like decreased solar activity or more pollutants in the atmosphere blocking sunlight, but more due to internal factors shifting the heat into the oceans.  In particular, the rate at which the deep oceans have warmed over the past 10 to 15 years isunprecedented in the past half century.

Research led by Masahiro Watanabe of the Japanese Atmosphere and Ocean Research Institute suggests this is mainly due to more efficient transfer of heat to the deep oceans. Consistent with model simulations led by Gerald Meehl, Watanabe finds that we sometimes expect “hiatus decades” to occur, when surface air temperatures don’t warm because more heat is transferred to the deep ocean layers.  A paper published last year by Yu Kosaka and Shang-Ping Xie from the Scripps Institution of Oceanography found that accounting for the changes in Pacific Ocean surface temperatures allowed their model to reproduce the slowed global surface warming over the past 10 to 15 years.  However, the mechanism causing these Pacific Ocean changes has remained elusive.

The new study published by Matthew England’s team helps explain how and why more heat is being funneled into the deeper ocean layers.  The study indicates that a dramatic acceleration in equatorial trade winds, associated with a negative phase of a cycle called the Interdecadal Pacific Oscillation (IPO) has invigorated the circulation of the Pacific Ocean.  This has caused more heat from the surface to be mixed down into deeper ocean layers, while bringing cooler waters to the surface. The combination of these two processes cools global surface temperatures.  Like the rate at which heat is accumulating in the deep oceans, the recent strengthening of the trade winds is unprecedented, as the bottom frame in the figure below shows.

Top frame: Global surface temperature anomalies. Bottom frame: Pacific wind stress anomalies. From England et al. (2014).

Not only is this acceleration of trade winds unprecedented, but it also far exceeds anything captured by climate models. Hence they have difficulty reproducing the recent slowdown in surface warming. The catch is that oscillations eventually change phases, so as England notes, the strengthened trade winds and faster rate of ocean heat accumulation are only temporary.

“the heat uptake is by no means permanent: when the trade wind strength returns to normal – as it inevitably will – our research suggests heat will quickly accumulate in the atmosphere. So global temperatures look set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade.”

The study estimates that by shifting more heat into the oceans, the strengthening trade winds can account for 0.1–0.2°C cooling of surface temperatures over the past 10 to 15 years. This would account for most of the slowed rate of warming, especially when combined with a recent study showing that the global surface warming slowdown is not as large as previously thought. The lead author of that paper, Kevin Cowtan said of this study,

“I think Professor England has uncovered the biggest piece in the puzzle of recent temperature trends”

In the figure below, the England study compares observed surface temperature changes (black and grey) with IPCC model projections (red), and projections made by models that incorporate these changes in trade winds (green and blue). The models including trade winds can reproduce the surface warming slowdown. However, once the IPO cycle shifts and winds return to previous levels, the models see an accelerated warming at the surface, and temperatures start to catch back up to the IPCC model projections.

A consistent picture is emerging in the climate research; increases in the strength of trade winds force more heat to be mixed down into the ocean, leading to a temporary slowing of rising surface temperatures. The next piece of the puzzle will involve explaining the cause of the dramatic, unprecedented trade wind acceleration. The IPO cycle can explain about half of the wind changes, but climate scientists are still investigating other possible contributing factors.

In any case, England concludes that surface temperatures may rapidly warm when the IPO phase shifts again in the next decade or so, and it will eventually be as though the surface warming slowdown never occurred.

“We should be very clear: the current hiatus offers no comfort – we are just seeing another pause in [surface] warming before the next inevitable rise in global temperatures.”

12 Responses to “Stronger Winds Shift Heat to Deeper Pacific”

  1. It is good to see articles on the minutia of heat exchange with the oceans system. I would hope it will lead to an improvement in the decadal forecasting in the near future. Similar to the resent improvements in El Niño Southern Oscillation which was restrictive to 6 months but now using newer analysis that can forest a year ahead now (but not the strength).

    It will be interesting to see what the kooks will say about the so called hiatus in the global mean surface temperature with the arrival of El Niño for later this year. (75% prediction).

    • dumboldguy Says:

      “It will be interesting to see what the kooks will say about the so called hiatus in the global mean surface temperature with the arrival of El Niño for later this year. (75% prediction)”.

      The “kooks” will be in a dither of denial, and will be going “but, but…” all over the place. (DB will be found sitting in a dark corner, rocking back and forth, and chanting “sea level rise is not accelerating”)

      From what I’ve been reading about it on Crock and other sites, the rest of us will likely be saying OMIGOD.

  2. kanspaugh Says:

    Hiatus! You said Hiatus! You can’t unsay it now that you’ve said it! Hiatus! Hiatus! Hiatus! –Watts

  3. skeptictmac57 Says:

    The next piece of the puzzle will involve explaining the cause of the dramatic, unprecedented trade wind acceleration.

    I wouldn’t put it past some of the religious fundamentalists in congress to explain it as “God blowing on the Earth to cool it down.Praise his name!”

    Look for it in the next testimony on climate change before congress.

  4. MorinMoss Says:

    Is it certain this is the cause of heat buildup in the lower ocean? Heat buildup is happening down to 2 km – that’s a LONG way down.
    Unless I’m mistaken, deep convection is only known to happen in a few places, mostly near the polar regions.

  5. […] 2014/02/11: PSinclair: Stronger Winds Shift Heat to Deeper Pacific […]

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