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

Xiaolong Zong,Fangjing Deng,Shuwen Zhang,Zhaoyun Chen,Ruzhen Zhang,Wei Zhou

doi:10.3390/jmse9121362

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.

Highlights

The number of extreme sea-level events is expected to grow due to the influence of global warming and climate change
We focus on the spatial and temporal changes of the 8.85-year cycle of N2 tide and the 4.42-year cycle of 2N2 tide in the Gulf of Maine and the Bay of Fundy and try to explain the long-term trend of tidal components and a quasi 20-year oscillation in the variation of the amplitude of these cycles
It should be realized that the number of independent points (IPs) plays a vital role in the results of the enhanced harmonic analysis (EHA)

Summary

Introduction

The number of extreme sea-level events is expected to grow due to the influence of global warming and climate change. This poses a more damaging threat to coastal areas, especially for the low elevation coastal zones, where up to 310 million people reside [1] and are accompanied by many infrastructures. An extreme sea-level indicator for the contiguous United States coastline has been recommended, which is comprised of separate indicators for mean sea level and storm surge climatology [3]. Extreme sea-level events are considered as a compounding effect of three factors: mean sea level (MSL), storm surge, and astronomical tides, if the effect of surface gravity wave is ignored [4]. Much focus has been paid to the change of MSL, and it is noted that

Methods

Results

Discussion

Conclusion