Present assessments of relative and absolute sea level rises at Alexandria, Egypt, and their predictions for 2050

Abstract The increase in sea level rise (SLR) during the 20th century is now a fact. Additionally, the lowlands in the Nile Delta region face challenges from vertical land movements, particularly land subsidence. The current research aims to monitor, analyze, and project both SLR and land subsidence at Alexandria city and forecast their hazards by 2050. To fulfill such objectives, heterogeneous geodetic datasets have been collected. The first one includes hourly tide data from 2008 to 2021. The second dataset consists of several annual observation files for a Global Navigation Satellite Systems (GNSS) station spanning the years 2012–2023. The obtained findings indicate that the present relative sea level rise at Alexandria equals 2.9 mm per year, which agrees with the current global average SLR estimate of 3.2 mm per year. Consequently, the anticipated mean sea level (MSL) for Egypt’s vertical national geodetic datum by the year 2050 is projected to be 0.374 m above the traditional datum. Furthermore, the analysis of GNSS data indicates that the current land subsidence rate at Alexandria is −1.5 mm per year. Factoring both the relative SLR and land subsidence, the absolute SLR at Alexandria by 2050 is estimated to be 0.414 m. The achieved results have been compared to those of the National Aeronautics and Space Administration (NASA) projection tool. Generally, the attained results agree with global estimates. It is recommended to get these findings into account for future engineering projects, coastal protection measures, and environmental initiatives in the city of Alexandria.