Evaluation of Sea Level Trends from Tide Gauge Data Along the Nigerian Coast

Sea level rise is among the most consequential manifestations of global climate change for low-lying coastal nations, and Nigeria's long coastline and densely populated coastal cities face heightened exposure to its impacts. This study analyses long-term sea level trends using tide gauge records from four operational stations along the Nigerian coast: Lagos, Forcados, Warri, and Calabar, drawing on digitised historical records and recent electronic gauge data spanning 1960 to 2023 where available. Monthly mean sea level time series are constructed from hourly gauge readings and subjected to quality control procedures to remove datum shifts, data gaps, and outlier readings. Linear trend analysis yields mean sea level rise rates expressed in millimetres per year, and comparison with satellite altimetry data from TOPEX/Poseidon and Jason missions provides validation and spatial context beyond the gauge locations. Inverse barometer corrections and wind-driven surge components are estimated to separate meteorological contributions from long-term sea level change signals. The study also computes return periods for extreme water levels to characterise coastal flood frequency distributions for each gauge site. Results are expected to indicate a mean sea level rise of 2.8 to 3.5 millimetres per year across stations, broadly consistent with global mean estimates but with significant local variability driven by land subsidence. Findings contribute to Nigeria's coastal hazard assessment framework and the National Adaptation Programme of Action. Keywords: sea level rise, tide gauge, Nigeria, coastal flooding, climate change adaptation