Exploring steric sea level variability in the Eastern Tropical Atlantic Ocean: a three-decade study (1993-2022)

Area of Science:

• Oceanography
• Climate Science
• Geophysics

Background:

• Sea level rise (SLR) threatens coastal populations globally, with over 60 million people in Africa living below 10m above sea level.
• The Eastern Tropical Atlantic Ocean (ETAO) is particularly vulnerable to SLR impacts.

Purpose of the Study:

• To analyze spatio-temporal trends of sea level anomaly (SLA) and its components in the ETAO from 1993 to 2022.
• To identify the drivers of SLR in the region and their correlation with climate factors.

Main Methods:

• Analysis of satellite altimetry data for SLA trends (1993-2022).
• Utilized ARMORD3D dataset for steric component analysis (thermosteric, halosteric).
• Incorporated GRACE and GRACE-FO mission data for ocean mass changes (2002-2022).

Main Results:

• ETAO exhibits an SLA trend of 3.52 ± 0.47 mm/year, consistent with the global average.
• Ocean mass changes dominate long-term SLR trends, while steric variations influence interannual variability.
• Warming observed along the equatorial African coast and Gulf of Guinea (GoG), with freshening near Angola.

Conclusions:

• Ocean mass, not steric expansion, is the primary driver of long-term sea level rise in the ETAO.
• Regional climate patterns significantly influence sea level changes.
• Urgent mitigation and adaptation strategies are crucial for vulnerable ETAO coastal communities.