Influence of the Pacific-South American modes on the global spectral wind-wave climate

Influence of the Pacific-South American modes on the global spectral wind-wave climate

In this study, we analyze the influence of the Pacific-South American modes (PSA-1 and PSA-2) on the global wind-wave climate using wave data derived from a WAVEWATCH III global wave hindcast. We apply an empirical orthogonal function analysis to daily-averaged directional wave spectra to extract the two main patterns of interannual wave spectral variability. These are related to changes in the wave spectral density levels (variability in the wave heights) and to rotations of the wave signal (variability in wave direction). The PSA-1 mode is positively correlated with the wave height variability in the southeast Pacific and negatively correlated in the Indian Ocean sector of the Southern Ocean. The PSA-2 mode presents a strong negative correlation with wave heights in the central South Pacific. Moreover, the PSA modes are significantly correlated with changes in modeled wave direction in the South Pacific region. Composite maps of wind anomalies during positive stages of PSA-1 and PSA-2 provide a compelling explanation for the observed correlation patterns. The methodology applied in this study is also used to assess the influence of other climate modes on the global wind-wave climate (namely, the Southern Annular Mode, Arctic Oscillation, North Atlantic Oscillation, El Niño/Southern Oscillation, and the Pacific North American mode). While our results are consistent with previous studies, we provide more clarity as to how different atmospheric modes influence the variability of specific components of the wave spectrum. Importantly, we assess how these climate modes would modulate the interannual variability of wave direction.