ESTIMATION OF SEA LEVEL ANOMALY ACROSS THE NIGERIAN COASTAL REGION USING SATELLITE ALTIMETRY TECHNIQUE

Abstract

The Sea level anomaly (SLA) phenomenon is one of the important global issues that is slowly threatening human survival and impairing economic development across the Nigerian coastal states. This phenomenon has significant impacts on the social economy, natural environment, and ecosystem of coastal areas. Multi-mission satellite altimeter data, reprocessed by data unification and combination system (DUAC) has offered a great opportunity for adopting active remote sensing technology in studying sea level changes. This study presents the SLA variation across Nigeria’s coastal zone using multi-mission satellite altimeter data for the period of fifteen years ((2006-2020) obtained from the Copernicus Marine Environment and Monitoring Services (CMEMS) portal. the monthly trend of the SLA was analysed for the period of study and the rate of SLA per year was determined; in addition, the future trend of the SLA variation along Nigeria's coast was predicted for thirty years at ten years intervals using a simple least square regression model. the results revealed a sharp high and low value of SLA from the year 2014 to 2017. This could be attributed to the effect of El-Nino and la-Nina effect. The estimated SLA value was validated using in-situ tide gauge stations located at Que Iboe Entrance in Akwa Ibom and Akaasa in Bayelsa States. The result was highly correlated with the in-situ data giving the correlation coefficient (R) of 0.8 at Que Iboe Entrance and 0.77 at Akaasa respectively. The predicted value of SLA presented a trend that indicates a rise of 0.125m in the years 2030, 0.140m in 2040, and 1.501m in 2050 at a 95% confidence level. However, the total area of about 2192 km3 in the coastal area is likely liable to be flooded by the rise in sea level. Therefore, there is a need to conduct more extensive research to ascertain the actual sea level anomaly over Nigeria's coastal water.