The Changing Global Climate and its Implication on Sea Level Trends in Tanzania and the Western Indian Ocean Region

Global mean sea levels show a general rising trend that has been accelerated by the recent changes in world climate. This is ascertained through geological and historical records, measurements from in situ tide gauges around the globe and since 1992, through satellite altimetry. About 60% of the 34 tide gauge stations in the Western Indian Ocean region with at least four years of data portray rising trends of relative sea levels, while the remaining 40% show falling trends. Sea level records in 14 other stations in the region were not considered in this investigation due to short data spans. Relative sea levels in Tanzania show falling trends in Tanga (1962-1966), Dar es Salaam (1986- 1990) and Zanzibar (1984-2004), but portray a rising trend in Mtwara (1959-1962). Published results from satellite altimetry (1993-2003) also concur with the national and regional tide gauge observations, and are similar to those observed in the Eastern Pacific. However, these patterns likely reflect inter-annual and decadal fluctuations rather than long-term trends. Available literature on model reconstructions of long-term sea level trends (1955-2003) show a general rising trend in Tanzania (0.4 to 2.0 mm/yr) and the Western Indian Ocean (-0.4 to 2.4 mm/yr). The global average within this period (-0.4 to 3.6 mm/yr) is basically higher than these national and regional trend