- Sea-level rise has accelerated across Africa in recent decades, thanks to global warming and, in particular, to the melting of ice sheets and glaciers, according to a recent study.
- Sea levels across the continent have risen four times faster since 2010, on average, than they had in the 1990s. About 80% of the sea-level rise is due to added water mass from meltwater.
- The impacts include flooding, erosion of coastal land, intrusion of salty seawater into freshwater drinking sources and displacement of coastal communities.
- In many coastal areas, sea-level rise occurs even as the land itself is sinking due to groundwater extraction or other factors, exacerbating its impacts.
Sea-level rise has accelerated across Africa in recent decades, thanks to global warming and, in particular, to the melting of ice sheets and glaciers, according to a recent study.
The study, published Dec. 15 in the journal Communications Earth & Environment, found that sea levels across the continent have risen four times faster since 2010, on average, than they had in the 1990s. The primary reason was additional water mass from polar melt, rather than other phenomena that can cause sea-level rise, the authors found.
“When you have ice-free summer [at high latitudes], it means that the water went somewhere,” Franck Ghomsi, a postdoctoral fellow at the University of Manitoba in Canada and lead author of the study, told Mongabay. “The glacier moved from ice to water, and it [water] started migrating. And it is the tropics [that] are now … getting this outflow of water.”
The impacts include flooding, erosion of coastal land, displacement of coastal communities and intrusion of salty seawater into freshwater drinking sources.
People in Africa are responsible for only a tiny proportion of human-caused global warming and yet face severe effects from the resulting sea-level rise, said Ghomsi, who is from Cameroon, calling this a “climate injustice.” He said that emissions from countries in the Global North are having a “huge impact” on countries in the Global South, including in Africa.
Accelerating sea-level rise
The current era of measuring sea-level rise began in the early 1990s with advancements in satellite altimetry, in which radar or laser pulses are bounced off the ocean’s surface. With knowledge of the satellite’s position and the time it takes for the signal to travel back, scientists can estimate sea levels.
This is one of the first studies to look at the sea-level situation for Africa as a whole, covering the oceans that surround the continent. Ghomsi and his co-authors primarily used altimetry data, as local field data are lacking. For example, there are very few long-standing, well-calibrated tide gauges located on the continent, he said. Tide gauges measure water level against a benchmark.
The authors found that the mean sea level in Africa rose by roughly 10.2 cm (4 inches) from 1993-2023, the study period. That figure is comparable to the global one, yet the trends in Africa are particularly alarming, they found. After a moderate uptick in the early 2000s, a notable acceleration occurred around 2010, with the vast majority of the sea-level rise in the study period occurring after that year. The continent’s waters reached their highest-to-date mean sea level in 2023 following a major rise related to an El Niño ocean warming event. The event continued into 2024 and the prior year’s was eclipsed, according to a narrower study led by Ghomsi that was published Jan. 19. El Niño warming events arise every few years as part of a cycle that starts in the Pacific Ocean and drives weather patterns around the world.
Spikes during El Niño years are nothing new, but the underlying conditions have changed. For example, there was a spike in 1997-98 that was “dramatic but temporary, sitting on top of a very weak underlying trend,” Ghomsi told Mongabay in an email. “What makes recent years alarming is that we are seeing sustained high levels, not just temporary spikes. The 2013 to 2023 decade shows 4.34 mm [millimeters of sea-level rise, or 0.2 inches] per year. That is not a spike that goes away. That is the new baseline.”
Leon Hauser, a postdoctoral researcher at the University of Zurich in Switzerland who’s studied sea-level rise in Africa, told Mongabay, in reference to Ghomsi’s December study, “Zooming in on Africa is an interesting perspective since the region has historically received less attention in the sea-level rise discussion.”
Hauser, who wasn’t involved with the study, said its results confirm predictions of an acceleration in sea-level rise made by the Intergovernmental Panel on Climate Change, a United Nations scientific body.
Meltwater more than thermal expansion
In addition to measuring sea-level rise in Africa, Ghomsi and his co-authors sought to determine which of two factors caused it. The ocean rises either because water is added, mainly through the melting of glaciers and ice sheets, or because existing water expands as it gets warmer or less salty. (As the concentration of dissolved salts in seawater decreases, it becomes less dense and the same mass of water takes up more space.)
However, directly measuring the addition of water is difficult, so they worked backward. Knowing the total sea-level rise from the satellite data, they figured out how much of it was caused by expansion and then concluded that the remaining was due to water addition.
To determine how much existing waters had expanded, they looked at changes in temperature and salinity using data largely from the Argo floats in the region. These cylindrical instruments are deployed by researchers in oceans across the world. This allowed the study authors to determine that not much of the sea-level rise was coming from expansion: only roughly 20%.
The remaining 80% of sea-level rise over the study period, they deduced, was from additional water. Globally, the addition and expansion components contribute almost equally to sea-level rise (addition accounts for only a bit more). This is not the case in Africa, as the study shows.
Ghomsi said this is due to local oceanography — cold-water upwelling that keeps some African surface waters cooler and salty conditions on the continent’s Mediterranean coast — and, even more so, to the way meltwater has been distributed, due to the effects of gravity and the Earth’s rotation, for example.
“When Greenland or Antarctica loses mass, the meltwater does not just spread out uniformly,” Ghomsi said.
While the long-term sea-level rise trend in Africa is caused primarily by additional meltwater, short-term fluctuations aren’t. The 2023-24 El Niño event brought with it unusual winds that disrupted the upwelling of cold water toward the surface. Heat got trapped, causing the water to expand. This expansion accounted for much of the sea-level rise during that two-year period, the follow-up paper found.
Lands in retreat, seas on the rise
For people living on the coasts of Africa, the problem of sea-level rise doesn’t exist in isolation: Oftentimes, it occurs as the land itself is sinking, or subsiding, due to groundwater extraction or other factors. This makes the relative sea-level rise (rSLR) even greater. In Lagos, Nigeria, a city of roughly 20 million people, the building of deepwater ports is the main factor in shoreline retreat, a 2022 study found.
Just as there are limited data from tide gauges, there are not enough to determine land subsidence and rSLR in many places in Africa, so assessing the risks of flooding and other threats is hard. Hauser led a 2023 study on rSLR for the coast of the Gulf of Guinea, which runs from Gabon to Liberia in western Africa, finding that certain sections of Nigeria, Benin, Ghana and Côte d’Ivoire were particularly at risk. Both the study and a follow-up briefing that Hauser co-authored emphasized the need for better field data on land subsidence and rSLR.
Ghomsi said the severe consequences that African communities face from sea-level rise should be a reminder that we live on “one planet” in which choices made in Global North countries reverberate across the globe.
Banner image: Camps Bay, Cape Town, South Africa. Image courtesy of Besir OZ via Unsplash.
Citations:
Ghomsi, F. E., Stroeve, J., Bonaduce, A., & Raj, R. P. (2025). Accelerating sea level rise in Africa and its large marine ecosystems since the 1990s. Communications Earth & Environment, 6(1). doi:10.1038/s43247-025-02965-z
Osanyintuyi, A. J., Wang, Y., & Mokhtar, N. A. (2022). Nearly five decades of changing shoreline mobility along the densely developed Lagos barrier-lagoon coast of Nigeria: A remote sensing approach. Journal of African Earth Sciences, 194, 104628. doi:10.1016/j.jafrearsci.2022.104628
Ghomsi, F. E., Stroeve, J., Crawford, A., Tamoffo, A. T., Mouassom, F. L., & Raogosha, M. (2026). 2023-2024 El Nino amplifies record sea level surges in African marine domains. Communications Earth & Environment. doi:10.1038/s43247-026-03204-9
Hauser, L., Boni, R., J. Minderhoud, P. S., Teatini, P., Woillez, M., Almar, R., … Addo, K. A. (2023). A scoping study on coastal vulnerability to relative sealevel rise in the Gulf of Guinea. Research Papers. Retrieved from https://www.afd.fr/en/ressources/scoping-study-coastal-vulnerability-relative-sealevel-rise-gulf-guinea
Seeger, K., J. Minderhoud, P. S., Hauser, L. T., Teatini, P., & Woillez, M. (2024). How to assess coastal flood risk in data-sparse coastal lowlands? Accurate information on land elevation is key. A Question of Development. Retrieved from https://www.afd.fr/en/ressources/how-assess-coastal-flood-risk-data-sparse-coastal-lowlands-accurate-information-land-elevation-key
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