Long term Sea Level Change in Nigerian Coastal Waters from Multi-Mission Altimetry Data

Abstract

The long-term sea level change from 2000 to 2015 was investigated within the Nigerian coasts of the Gulf of Guinea and the Atlantic Ocean from satellite altimetry data of the TOPEX, JASON-1, JASON-2, ERS-2, ENVISAT and SARAL missions. Sea level data retrieval and reduction were carried out using the radar altimeter database system (RADS). In RADS data processing, the 2008 updated environmental and geophysical corrections were applied. Three tidal stations were chosen for the altimetry data comparison in order to ascertain the correlation that exists between the ocean tide models selected for the study. Similarity in the patterns of sea level variations indicates good agreement between altimetry data independently obtained with GOT4.10 ocean tide model (OTM)and FES2004 OTM. From the 16 years’ altimetry data, results from both ocean tide model show positive sea level trend within the region. The altimeter sea level time series revealed that since 2000, the mean sea level in Nigerian coasts has been rising at a geographically-dependent rate of 2.4mm/year and 3.6mm/year with the GOT4.10 and FES2004 OTMs respectively. Also, both ocean tide models vary in the estimated sea level trends by 1.2mm/year and have a root-mean-square difference of 1.3cm. This kind of information is important for better understanding of the marine ecosystem; studying environmental issues related to flood investigations and global warming especially for an area that until now is yet to be adequately explored by the altimeter science community.