Interannual and longer time-scale sea level changes are relatively small amplitude. However, they can provide background conditions favorable for the occurrence of extreme sea levels that represent a threat for coastal communities, especially in low-lying and flood-vulnerable regions. A new study accepted in Geophysical Research Letters identified the dominant mode of the ocean gyre-scale sea surface height (SSH) variability in the North Atlantic (i.e., North Atlantic SSH tripole) and showed that this mode is responsible for most of the interannual-to-decadal SSH changes along the southeast coast of the United States. The study also show that these changes are largely driven by the large-scale heat divergence related to the Atlantic Meridional Overturning Circulation (AMOC) and linked to the low-frequency North Atlantic Oscillation.
Figure 1 from Volkov et al. (2019): (a-d) The first Empirical Orthogonal Function (EOF1) of the interannual sea level variability (i.e., North Atlantic SSH tripole); (a) EOF1 of SSH explaining 26.7% of the interannual SSH variance; (b) EOF1 of steric sea level (SSL) explaining 47.9% of the interannual SSL variance; (c) EOF1 of thermosteric sea level (TSL) explaining 44.6% of the interannual TSL variance; (d) temporal evolutions (PC1) of EOF1 of (blue) SSH, (black) SSL, and (red) TSL. The approximate location of the RAPID/MOCHA/WBTS observing array is shown by the dotted blueline. (e) Portion of the local interannual SSH variance (%) explained by EOF1; the location of tide gauges used in the analysis is shown by circles. (f) Regression map of (color) SLP on PC1 and (arrows) wind velocity on PC1; the units are Pa per standard deviation of PC1 and m/s per standard deviation of PC1, respectively.
Volkov, D., S.-K. Lee, R. Domingues, H. Zhang, and M. Goes, 2019: Interannual sea level variability along the southeastern seaboard of the United States in relation to the gyre-scale heat divergence in the North Atlantic. Geophys. Res. Lett., 46., https://doi.org/10.1029/2019GL083596, https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083596