Abstract
QUANTIFICATION OF SEA LEVEL RISE USING MULTI-MISSION SATELLITE ALTIMETRY DATA OVER NIGERIAN TERRITORIAL WATERS
Okafor Somtoochukwu Chukwunonso* and Uzodinma Victus Ndubuisi
ABSTRACT
Many low-lying and vulnerable coastal areas especially the Nigerian coastlines are threatened by global sea level rise. Human lives and economic assets such as sea ports and tourism centres are threatened. This study assesses these threats by quantifying sea level variations and trends off the Nigerian coastline using measurements from multiple altimeter missions over 1993?2016. Sea level anomalies (SLAs) data were extracted from 9 satellite altimeter missions namely: TOPEX/ Poseidon, Jason-1, Jason-2, Jason 3, ERS-1, ERS-2, EnviSat, CryoSat-2 and SARAL. Sea level trends were determined by using moving average and time series linear regression analysis of both monthly and yearly averaged SLA solutions. The result showed that rate sea level rise trends over Nigerian territorial waters just off the coastline ranges from 2.23 ? 0.39 mm/yr to 4.90 ? 0.41 mm/yr. Over 1993?2016, the mean rising rate within the study area is 3.25 ? 0.65 mm/yr. Tidal SLA measurements of Sao Tome tide gauge station at Sao Tome and Province was used to validate SLAs from altimetry. The assessment result shows similar patterns of SLAs with high correlation coefficient of 90% and small root mean square differences (RMSE) of 3.62 cm between SLAs from altimetry and tide gauge over the same period. Predictions were made based on the assumption that sea level rise is constant every year, the obtained predictions as shows that sea level rise off the Nigerian coastline will be 0.18 ? 0.21 m by the year 2041, 0.42 ? 0.49 m by the year 2066, 0.66 ? 0.77 m by 2091 and 0.90 ? 1.05 m by the year 2116. For the few areas where the comparison in elevation of some coastal areas and the sea was done, the results showed that the difference ranges between 0.4 ? 1.0 m. This study predicted the impact of such rising sea levels on the Nigerian coastal areas and proffers remedial measures to mitigate such impacts.
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