Pacific climate phases occasionally "lock" into phase

Like waves on an ocean, different climate cycles will occasionally synchronize—but two Pacific cycles not only briefly synchronize but then “lock” into phase.

This locking synchronization was described in the September issue of Physical Review Letters by Karl Stein, a University of Hawai`i at Mānoa PhD student, and Axel Timmermann and Niklas Schneider, professors at the UH Mānoa International Pacific Research Center and the Department of Oceanography.

Two of the known cycles in the equatorial Pacific are the seasonal variation in temperatures and the El Niño-Southern Oscillation, which operates on a cycle ranging from 2 to 7 years in length.

The scientists identified patterns in which these difference cycles occasionally fall into synchronization and seem to lock there for a period of time, while at other times, they simply cross paths and fail to synchronize.

It suggests that in Niño and in the tropical Eastern Pacific annual cycle, there is some feedback going on, such that once they coincide, they somehow remain in synch for a period of time, rather than continuing on their own cycles.

The next question is why that happens and what it means.

“The newly discovered sporadic phase-locking behavior of El Niño and the annual cycle will have significant impacts on current understanding of the seasonal predictability of large El Niño events. The scientists are eager to test how well state-of-the art climate models reproduce the nonlinear interaction between these two dominant modes of climate variability,” the authors said in a press release.

They said this kind of phase locking was first described in 1673 by the Dutch scientist Christiaan Huygens. It is the kind of thing that infrequently happens, for example, when an applauding audience suddenly starts to clap in unison and continues doing so for a period of time.

Citation: Karl Stein, Axel Timmermann, and Niklas Schneider, 2011: Phase Synchronization of the El Niño-Southern Oscillation with the Annual Cycle, Phys. Rev. Lett., 107, issue 12.

The research was supported by the Office of Science (BER) of the U.S. Department of Energy, and by NASA, NOAA, and the Japan Agency for Marine-Earth Science and Technology which sponsor research at the International Pacific Research Center.

© Jan TenBruggencate 2011