Analysis of Sea Level Changes in Eastern Taiwan Coast—Case of Yilan Area

Abstract

This study considers the impact of extreme climates on most of the world’s land and seas, which may cause the average sea level to rise due to global climate change. Affected by the rise of sea level, it will change the distribution characteristics of sea tides, waves and currents. When the distribution of tides, waves and currents in the sea area changes, it may cause changes in the overall environmental characteristics of the estuary and coastal areas, and further affects the function of coastal protection facilities. This study takes the sea area of Yilan as an example, and analyzes the problem of sea level rise in the three-in-one climate change (including sea level rise, typhoon and heavy rain). For the analysis of sea level rise, this study calculates tide level data in three ways, the first is simple moving average (SMA), then there are empirical mode decomposition (EMD) and ensemble empirical mode decomposition (EEMD) in the hilbert-huang transform (HHT) for sea level rise analysis. The use of ensemble empirical mode decomposition (EEMD) is because when modal confusion occurs in empirical mode decomposition (EMD), the occurrence of modal confusion can be reduced by adding the decomposed signal to the white noise sequence. Comparing the analysis results of the three respectively, the result obtained by using simple moving average (SMA) is the smallest (2.78 mm/yr), and the result obtained by using ensemble empirical mode decomposition (EEMD) calculation is the largest (4.11mm/yr). By analyzing the results obtained, it can be provided for assessing future hydrological and environmental changes based on climate change conditions.