Influence of the Pacific‐South American Modes on the Global Spectral Wind‐Wave Climate. Issue 8 (13th August 2020)

• Record Type: Journal Article
• Authors: Echevarria, E. R.; Hemer, M. A.; Holbrook, N. J.; Marshall, A. G.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-13
• Subjects: wind‐waves -- Pacific‐South American modes -- spectral wave climate -- climate modes -- empirical orthogonal function analysis; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2020JC016354
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: 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. Plain Language Summary: Different modes of atmospheric variability (such as El Niño/Southern Oscillation or the Southern Annular Mode) are known to influence the ocean wind‐wave climate in many regions of the world and across different timescales. The Pacific‐South American (PSA) patterns represent important modes of variability of the atmospheric circulation in the Southern Hemisphere. In this study we use results from an ocean wind‐wave model to analyze how the PSA patterns influence the global wave field. We apply a methodology that allows us to study in detail changes in wave height and direction. Our results suggest that the PSA modes would be associated with wind anomalies that modulate the height and direction of swell waves generated in the Southern Ocean, particularly in the south Pacific. We also analyze other climate modes of variability and their influence on the wind‐wave field. Our results are consistent with previous studies, and they suggest that the influence of the PSA modes on the wind‐wave field is of the same order of magnitude as that of other climate modes. Key Points: The influence of the Pacific‐South American (PSA) modes on the global spectral wind‐wave climate is analyzed The PSA modes are significantly correlated with the variability of modeled wave heights and directions in the south Pacific Composite wind anomalies for positive stages of PSA modes are shown to explain the observed correlation patterns