Abstract
The advent of technology in the world has led to enormous, varying economic and social changes. Those changes have influenced the climate balance, which leads to global temperature rise, hence oceanic expansion and melting glaciers. These various phenomena caused the variation in the mean sea level. Thus, in this study we have evaluated that variation from the instrumental recordings of the tide gauges available in the region, which led us to choose the tide gauges of Dakar (Senegal), Nouakchott (Mauritania) and Palmeira (Cape Verde). The analysis of the tidal series began with the test of presence or absence of significant trends in the series using the Man-Kendall method followed by the decomposition of these series using the SSA, ARIMA and SLT techniques, which would result in the trend, seasonality and residues. The results of this analysis show a variation of 1.52 mm/year, 4.51 mm/year and 20.08 mm/year respectively for the Dakar, Palmeira and Nouakchott tide gauges.
Highlights
The sea level has changed on various time scales
In this study we have evaluated that variation from the instrumental recordings of the tide gauges available in the region, which led us to choose the tide gauges of Dakar (Senegal), Nouakchott (Mauritania) and Palmeira (Cape Verde)
The results of this section relating to the Mann-Kendall trend test are obtained through the “trend” package [25] developed in the R environment
Summary
The sea level has changed on various time scales. During the last ice age, around 20,000 years ago, the sea level was on average 120 m lower than today. Eustatic sea level rise has subsequently occurred at an average rate of 0.5 mm per year for the past 6000 years, and 0.1 to 0.2 mm per year for the past 3000 years This rate is about 10 times lower than that observed in the 20th century. The trend component is used to determine the changes in sea level during the period considered This trend will highlight the slow rise in mean sea level under the combined effect of thermal expansion due to steric effect, melting ice and glaciers, precipitation, etc. The seasonality component is used to determine the cycle of sea level variation, valid for the period covered by the series of tide measurements and from which the effects due to changes in the trend or in noise are eliminated. The conclusions of this study are presented in the last section
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