## Results  
The Indian Ocean has four long-term trend tide gauges, three of which are segmented. An example of a segmented tide gauge record is Aden, where data have been collected over 135 years in five segments, with gaps totaling 67 years, by using different tide gauges [21]. Mumbai [2] and Karachi [3]are other remarkable examples of segmented tide gauge records. In Mumbai, data have been collected in five segments over 134 years, with gaps totaling 12 years, by using different tide gauges. In Karachi, data have been collected in four segments over 99 years, with gaps totaling 43 years, by using different tide gauges. There are concerns for the alignment of all the different segments of the three composite tide gauge records of Aden, Mumbai, and Karachi because the trends within the individual segments are mostly stable, and it is only their composition that produces a positive slope [2; 3; 21]. The present contribution proposes a procedure to check the alignment of segments when there is doubt about their misalignment. Figure 2 presents a satellite view of the Indian Ocean, with the location of the Fremantle and Mumbai tide gauges indicated with an arrow. The figure also presents the main warm and cold currents for the area. Figure 3 presents the MSL of Aden, Mumbai, and Karachi. The figure also presents the MSL of Fremantle, the other long-term tide gauge of the Indian Ocean. Opposite to Aden, Mumbai, and Karachi, Fremantle is not a segmented record. In the pictures, from sealevel.info (www.sealevel.info), the MSL is claimed to be clear of the regular seasonal fluctuations due to coastal ocean temperatures, salinities, winds, atmospheric pressures, and ocean currents. The clearing process includes quite complicated operations that might be doubted, however marginally affecting the computed trends. Figure 3a,b presents the MSL for Aden, with data from NOAA (tidesandcurrents.noaa.gov/) and from PSMSL. Figure 2: (a) Satellite image of the ocean basin under study. Image reproduced and modified from www.psmsl.org/products/trends/. Warm and cold major currents for the area. (b) Image reproduced and modified from [[https://en.wikipedia.org/wiki/Ocean_current#/media/File-Corrientes-oceanics.png](https://en.wikipedia.org/wiki/Ocean_current#/media/File-Corrientes-oceanics.png)]([https://en.wikipedia.org/wiki/Ocean_current#/media/File-Corrientes-oceanics.png](https://en.wikipedia.org/wiki/Ocean_current#/media/File-Corrientes-oceanics.png)). The data from NOAA are simply an earlier version of the PSMSL data. The earlier version still available from NOAA is called (\(n-1\)), and the latest version from PSMSL is called (\(n\)). As the databases of climate parameters are unfortunately unstable, it is common to have historical data revised from one version to the other. Figure 3: _Cont._  
From a summary examination, the record for Aden includes two major gaps and one short gap. In Aden version (\(n-1\)), Figure 3a, with the date range March 1879 to December 2010, the slope is \(3.067\pm 0.222\) mm/yr and the acceleration is \(-0.0237\pm 0.0099\) mm/yr\({}^{2}\) (negative). In Aden version (\(n\)), Figure 3b, with date range March 1879 to October 2013, the slope is \(+1.258\pm 0.156\) mm/yr, and the acceleration is \(+0.01478\pm 0.00668\) mm/yr\({}^{2}\) (positive). Figure 3c presents the MSL for Mumbai. From a summary examination, it includes one gap. With the date range January 1878 to November 2011, the slope is \(+0.796\pm 0.095\) mm/yr and the acceleration is \(+0.00664\pm 0.00538\) mm/yr\({}^{2}\). Figure 3d presents the MSL for Karachi. From a summary examination, it includes three gaps. With the date range January 1916 to December 2014, the slope is \(+1.850\pm 0.519\) mm/yr and the acceleration is \(+0.0584\pm 0.0324\) mm/yr\({}^{2}\). Figure 3e presents the MSL for Frematle. There are no gaps in this record. With the date range January 1897 to December 2016, the slope is \(+1.694\pm 0.246\) mm/yr and the acceleration is \(+0.00571\pm 0.01567\) mm/yr\({}^{2}\).