Seasonal-to-decadal modes of global sea level variability derived from merged altimeter data

Motivated by the first availability of more than 16 years (1992–2009) of merged altimeter data from up to four concurrent satellite missions with TOPEX/Poseidon, ERS-1 and 2, ENVISAT, Jason-1, and Geosat Follow-On, the global sea level is reexamined with special emphasis on its distinctive scales of variability. The global sea level variability is dominated by eleven statistically significant and geographically robust principal modes at seasonal-to-decadal timescales. The identified modes can be divided into four regimes, i.e., the seasonal regime with two principal components at 3 and 6 months, the annual regime with a single 12-month component of global dominance, the interannual regime with seven principal components at 1.55, 1.74, 1.94, 2.34, 3.07, 4.20, and 5.40 years, as well as the decadal regime with a 9.28-year subdecadal component. The frequency dispersion of the identified modes is found to be at ∼ 0% level for the annual regime, at ∼ 5% level for the seasonal and interannual regimes, and at ∼ 10% level for the decadal regime. In the space domain, the locations of principal modes are found to be geographically correlated. The seasonal regime is characterized by a small number of localized amplitude highs in regional seas. The annual regime is associated with major western boundary currents of the Gulf Stream and Kuroshio. For the interannual regime, mode active zones are observed in the western Pacific warm pool (WPWP), El Niño, and western Indian Ocean regions, among which the WPWP has a well-defined two-core structure, and the northern core coincides with the most energetic zone of the decadal regime. Another interesting finding is that east–west (zonal) and equatorial–extratropical (meridional) teleconnections are evident for the major signals in a rather symmetric and systematic pattern. Joint spatiotemporal analysis reveals that multi-modality at a given location and multi-regionality for a given mode are fundamental features in global sea level variability.