Rapid change in semi-diurnal tides in the North Atlantic since 1980

[1] An anomalously large trend of M2 and S2 amplitudes and phases, beginning in the early 1980s, is observed in the North Atlantic. Harmonic analysis of long-term sea-level records from tide-gauge stations along the North American Atlantic coast and European Atlantic coast shows a large decrease in M2 and S2 amplitudes and an increase in phase lag. The characteristics of the evolution of M2 and S2 tides are similar, but not fully conclusive, which may suggesting different causes. In general, the trends may be due to global warming, which significantly increased in the early 1980s in the North Atlantic region. Several climate-related driving mechanisms for the observed changes in tides are discussed.