Differences in Maximum Tides Responses of the North Coast and the South Coast of Java on the Effects of the Position of the Moon and the Sun

Abstract

Abstract The influence of the earth-moon-sun system on tide events has long been known. However, the impact can vary in different coast areas. The short-term (monthly and yearly) impact of maximum tides needs to be watched out for in relation to tidal flooding, especially if it is reinforced by bad weather at sea. In 2021 NASA reported the results of the Sea Level Change Science Team study that in the 2030s tidal floods will become more frequent and threatening the coasts of the United States due to the 18.6-year lunar orbit nodal cycle which amplifies the effects of global warming. Analysis of maximum tides on the north coast of Java (using data from Jakarta and Surabaya) and on the south coast of Java (using data from Cilacap) shows that on both the north and the south coast of Java, there is no indication of the nodal cycle of the 18.6 year due to lunar orbit. However, this study shows that in short-term annual and monthly cycles there is a difference in the pattern of maximum tides on the north coast and the south coast of Java. The declination of the sun when it is most northerly (the end of June) and most southerly (the end of December) affects maximum tides on the north coast of Java, as semi-annual cycle. Meanwhile on the south coast of Java, only the southernmost declination of the sun (in the end of December) has an effect on the maximum tide, as annual cycle. For monthly cycles, maximum tides on the north coast of Java are affected by the maximum declination of the moon and moon’s perigee (in Jakarta) or by the moon phases and perigee (in Surabaya). Meanwhile, on the south coast of Java it is only affected by the moon’s phases and perigee.