Monitoring Climate Change Induced Sea Level Rise in Kenya

The Intergovernmental Oceanographic Commission (IOC) of UNESCO developed a Global Sea Level Observing System (GLOSS) program in 1985 to address the growing concern about the rise in mean sea level around the globe. Kenya is actively participating in GLOSS and has already received support and assistance in terms of training of our specialists and provision of equipment through IOC. There are two sea level monitoring stations in Mombasa and Lamu being managed by KMFRI. Both are Principal station on the GLOSS network and also dedicated components of the Indian Ocean Tsunami Warning System (IOTWS).

Time series of hourly sea level data for Mombasa (1986 to date) and Lamu (1996 to date) can be obtained from KMFRI. Real-time data transmission from both stations can be accessed on the global sea level database hosted by the University of Hawaii Sea Level Centre (UHSLC) and IOC of UNESCO websites.

In this exercise we have (i) collected and analysed one-year hourly sea level data from Mombasa and Lamu and generated tidal predictions for the two stations for the period 1st January to 31st December 2023, (ii) Disseminated the comprehensive tide tables produced by KMFRI by distributing them to stakeholders and (iii) Build-up sea level database for detection of extreme oceanic events.

Harmonic analysis method was applied to extract sinusoidal components of specific frequencies from time series of observed hourly water levels to generate tide predictions for Mombasa and Lamu ports.

Water level variations in Mombasa station are typically semi-diurnal with spring tide range of 3.12 m and neap tide range of 1.07 m. The corresponding values for Lamu are 2.93 m and 0.99 m respectively. From harmonic analysis results, semi-diurnal tides are the primary drivers of tidal forcing. Astronomical tides account for more than 90% of the water level variations. Tide tables for both Mombasa and Lamu reveals that Kenyan coastline experiences two high tides and two low tides of unequal heights in a period of 24 hours, typical semi-diurnal tidal patterns. As indicated by the residuals, meteorological forcing due to wind stress or fluctuations in air pressure plays a minor role in the water level variations.

Monthly means of sea level data for Mombasa station reveals a trend of rise in MSL of 2mm per year which is consistent with the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).