The identification of the behaviours in tide gauges with time series analysis: Example of TUDES tide gauges stations

It is important to determine the sea level for the scientific fields that study the earth such as Geodesy, Geophysics, Geodynamics, Hydrology and Oceanography. Determination of the sea level is used in geodetic studies especially to determine the vertical datum required for height systems; to identify Mean Sea Level (MSL) together with Sea Surface Topography (SST) and the movement of vertical crustal areas near the tide gauge stations. Changes in the sea surface occur as a result of sudden land displacements triggered by earthquakes and tectonic movements that are caused by the gravity effect of the sun and the moon. Changing in the sea levels can be specified by using satellite altimetry technique or obtained data from tide gauges established on coastlines. In this thesis study, monthly mean sea level data of 10 tide gauges of Turkish National Sea Level Monitoring System (TUDES) are used for determining sea level changes between 1984-2009. Time series analysis has been used to determine the long-term changes of the sea level in tide gauges. In time series analysis, Trend Component Analysis is performed using Least Squares (LS) and Periodic Component Analysis is performed using Fast Fourier Transform (FFT).