Over the past decades, the sea level in the western Pacific rose up to three times faster than the global mean, while its counterpart in the eastern Pacific including U.S. west coast was nearly stationary or decreasing [Moon and Song, 2013; Moon et al, 2013]. In fact, the regional seal-level trends have undergone two shifts, during the mid-1970s and in the early 1990s, with an east-west dipole pattern in the tropical Pacific. In each of these phases, the regional sea levels accelerated on one side of the Pacific, but decelerated on the other side. It is puzzling how long this pattern of regional sea level changes has been gone, what is the dynamic cause, and how these can affect deep ocean. These regional sea level changes, when superimposed on the global trend of sea level rise, could have profound implications for coastal communities and the health of marine and estuarial habitats. In this study, we have examined recently reconstructed long-term sea level data products, upper-ocean measurements, satellite data, and a mass-conserving OGCM results [e.g., Song and Colberg 2011] to gain insight into the puzzling swings of the Pacific sea levels. We will show that (1) the multi-decadal sea-level swings are the consequence of upper-ocean heat changes, closely related to the Pacific Decadal Oscillation (PDO)-induced ocean circulations [Moon et al., 2015]; (2) the dueling climate cycles, PDO and ENSO, may have intensified the sea level swings in the tropical Pacific since 1980s [Cha et al. 2018]; and (3) the relative roles played by the local/Pacific atmospheric forcing and the global ocean circulation are examined to explain the underling dynamic mechanisms.
Reference:
Cha, S.-C., Moon, J.-H., & Song, Y. T. (2018), A recent shift toward an El Niño-like ocean state in the tropical Pacific and the resumption of ocean warming. Geophysical Research Letters, https://doi.org/10.1029/2018GL080651 (highlighted by EOS Research Spotlights).
Moon, J.-H., Y. T. Song, and H. Lee (2015), PDO and ENSO modulations intensified decadal sea level variability in the tropical Pacific, J. Geophys. Res. Oceans, 120, doi:10.1002/2015JC011139.
Moon, J.-H., Y. T. Song, P. D. Bromirski, and A. J. Miller (2013), Multidecadal regional sea level shifts in the Pacific over 1958–2008, J. Geophys. Res. Oceans, 118, doi:10.1002/2013JC009297 (Joint AGU-NASA press-release, March 2016).
Moon, J.-H. and Y. T. Song (2013), Sea level and heat content changes in the western North Pacific. J. Geophys. Res. Oceans, 118, 2014-2022, doi:10.1002/jgrc.200.
Song, Y. T. and F. Colberg (2011), Deep ocean warming assessed from altimeters, Gravity Recovery and Climate Experiment, in situ measurements, and a non-Boussinesq ocean general circulation model, J. Geophys. Res., 116, C02020, doi:10.1029/2010JC006601.