Africa’s coastlines are facing a rapidly accelerating crisis, marked by the 2023–2024 El Niño event, which has triggered the most significant sea level surge ever recorded in the region. This unprecedented rise highlights a dangerous new reality for the continent’s 38 coastal nations. A comprehensive study, published in Communications Earth & Environment, was conducted by researchers from the department of oceanography at the University of Cape Town (UCT). They meticulously analyzed over 30 years of satellite data, spanning from 1993 to 2024, across the Atlantic Ocean, Indian Ocean, Mediterranean Sea, Red Sea, and surrounding waters.

While the global impacts of the 2023–2024 El Niño have been extensively documented, its specific effects on Africa’s sea levels had received significantly less attention. The UCT study revealed early evidence that the event coincided with unusually warm ocean temperatures along almost the entire African continent. In some parts of West Africa, sea surface temperatures rose by more than 2°C, with “nearly the entire coastline of Africa experienced anomalously high sea surface temperatures in 2023–2024.” These conditions were accompanied by elevated sea levels, intensifying storm surges, driving saltwater into freshwater systems, and accelerating coastal erosion.

A critical challenge for researchers was to differentiate how much of these extreme conditions could be directly attributed to El Niño and how much reflected other climate systems or the long-term rise in sea levels. This uncertainty is particularly troubling for Africa, a continent already highly vulnerable due to limited monitoring infrastructure, sparse tide gauge coverage, and a heavy reliance on marine resources, leaving its coastal communities exposed. The past two years have underscored this risk, with severe marine heatwaves disrupting fisheries and compounding existing food and economic insecurity.

The study’s analysis of high-resolution satellite data aimed to close this crucial gap in understanding, examining how El Niño-driven variability interacts with the ongoing long-term sea level rise. Their findings indicated that regional sea levels have risen by 11.26cm since 1993, a rate that outpaces the global average. Furthermore, this rise is accelerating at a rate of 0.14mm per year squared, which is faster than previously documented. When the long-term trend of rising seas is removed to isolate the effect of natural climate cycles, the 2023–2024 El Niño produced a staggering sea level anomaly of 27mm, marking it as the largest on record. This figure dwarfs the 1997–1998 El Niño, one of the most powerful climate events of the 20th century, which produced a smaller anomaly of about 19mm.

What made the 2023–2024 event truly extraordinary was not El Niño alone, but a rare and dangerous alignment of multiple climate patterns that occurred simultaneously. The Indian Ocean Dipole, the Atlantic Niño, and the Tropical North Atlantic index all reached record-positive levels prior to and during this period. This rare convergence effectively preconditioned the ocean, amplifying El Niño’s impact far beyond what its individual strength might have predicted. The Indian Ocean Dipole is a “see-saw” of ocean temperatures that can warm waters along East Africa. The Atlantic Niño is a similar warming event in the equatorial Atlantic, affecting West African coasts. The Tropical North Atlantic index measures unusually warm water in the tropical North Atlantic, influencing winds and currents.

Dr. Franck Ghomsi, the study’s lead researcher and a postdoctoral fellow at the Nansen-Tutu Centre for Marine Environmental Research at UCT, explained that what is being witnessed is a fundamental shift in how the ocean responds to climate variability. He stated, “The 2023–2024 event interacted with an ocean already preconditioned by multiple climate forces and excessive heat, creating a compound effect that pushed sea levels to heights we have never seen in the satellite record.” Thermal expansion, the physical swelling of water as it heats up, accounted for more than 70% of the total rise during this event, effectively meaning the ocean was experiencing a fever.

Compounding this issue, typical wind patterns that usually bring cold, nutrient-rich water up from the deep ocean along Africa’s coasts effectively shut down. This led to hot surface water piling up along the coastline. Concurrently, the ocean became highly stratified, or layered, trapping heat near the surface and preventing it from mixing into deeper, cooler waters. The result was a quadrupling of ocean heat content compared to previous events, establishing a feedback loop that locked ever more warmth near the surface and drove sea levels even higher.

The study identified a critical turning point around 2009, when sea level rise accelerated by a dramatic 73%. Before 2009, levels rose at 2.72mm per year; afterwards, that rate surged to 4.70mm per year. The 2023–2024 period alone contributed 2.34cm—roughly one-fifth of all sea level rise recorded since 1993. The authors warn that this acceleration poses severe risks to Africa’s 38 coastal nations, where more than 15 million people in major coastal cities such as Lagos, Douala, Accra, and Dar es Salaam now face heightened flood risk. For Small Island Developing States like the Seychelles and Comoros, every millimeter of rise directly threatens critical infrastructure, freshwater supplies, and ultimately, habitability.

The crisis extends beneath the waves, profoundly impacting marine ecosystems. The suppression of cold, nutrient-rich water, a consequence of the processes driving higher sea levels, disrupts these vital systems. Fisheries, which provide essential food and income for millions of Africans, are under increasing stress, threatening biodiversity and food security across West Africa and island communities. Dr. Ghomsi emphasized, “This research closes a critical knowledge gap regarding African sea levels. But knowing the data is only the first step. We must use this information to drive policy, build resilient infrastructure and protect the vulnerable ecosystems and communities that define our continent’s coastline.” The study offers an integrated perspective on how climate variability and long-term warming combine to shape coastal risk, providing insights that could strengthen early warning systems and support adaptation efforts. The researchers unequivocally stressed that Africa’s coastlines are emerging as crucial early warning indicators of compound climate hazards, where the convergence of long-term warming and extreme events profoundly amplifies risk. They advocate for expanded ocean monitoring, robust early warning systems, and coordinated regional adaptation strategies to effectively confront the challenges posed by a rapidly changing ocean climate.