An Analysis of the 8.85- and 4.42-Year Cycles in the Gulf of Maine

Abstract

In the background of global warming and climate change, nuisance flooding is only caused by astronomical tides, which could be modulated by the nodal cycle. Therefore, much attention should be paid to the variation in the amplitude of the nodal cycle. In this paper, we utilize the enhanced harmonic analysis method and the independent point scheme to obtain the time-dependent amplitudes of the 8.85-year cycle of N2 tide and the 4.42-year cycle of 2N2 tide based on water level records of four tide gauges in the Gulf of Maine. Results indicate that the long-term trends of N2 and 2N2 tides vary spatially, which may be affected by the sea-level rise, coastal defenses, and other possible climate-related mechanisms. The comparison between Halifax and Eastport reveals that the topography greatly influences the amplitudes of those cycles. Moreover, a quasi 20-year oscillation is obvious in the 8.85-year cycle of N2 tide. This oscillation probably relates to a 20-year mode in the North Atlantic Ocean.

Nodal modulation of M2 and N2 tides along the Norwegian coast

“…Fortunately, researchers have acknowledged this challenge, leading to the development of an effective method known as enhanced harmonic analysis (EHA, Jin et al, 2018). The nodal cycle is treated varying with time in the EHA method, and the method has been applied successfully to explore the temporal changes of nodal modulation in the gulfs of Maine and Tonkin (Pan et al, 2019;Zong et al, 2021;Pan et al, 2022).…”