Effects of Low-Frequency Oscillations of Global HCIs on Long-Term Sea Levels in the Western Hemisphere

Abstract:

As many coastal locations throughout the globe have recently experienced accelerated sea level rise, an attempt is made to better understand the extent to which global climate variability can be linked to long-term sea levels. Correlations between average sea levels at sites along the coasts of North, Central, and South America and low-frequency oscillations of the mean activity of 30 hydro-climate indices (HCIs) are analyzed using correlation analysis and sliding window sizes on the order of years to reduce the effects of high-frequency variability in the time series. The strength of each relationship is assessed using the Pearson’s correlation coefficient (r), while significance is estimated using Leave-One-Out Cross Validation (LOOCV) in addition to a bootstrapping technique. The sliding window size, lag time, and beginning month were varied to produce the optimal correlation at each measurement site; a 48-month sliding window and 0 lag time resulted in the strongest correlations. Strong (r > 0.60 and significant (p-value < 0.05) correlations with 7 primary HCIs were identified. The Tropical South Atlantic index (TSA) and the Western Hemisphere Warm Pool (WHWP) were found to exhibit the strongest and most widespread correlation with sea level, while other HCIs that were also identified as having a strong link with sea level at a smaller number of sites include the Atlantic Meridional Mode (AMM), the Atlantic Multidecadal Oscillation (AMO), the Caribbean Index (CAR), the Madden-Julian Oscillation (MJO), and the El Nino/Southern Oscillation (ENSO). The final results of this study allow a greater understanding of potential links between climate variability and long-term sea levels throughout the Western Hemisphere, leading to potentially more confident predictions of long-term changes in sea levels and an enhanced understanding of the roles of climate variability vs. climate change on current and future rates of sea level rise.