Satellite data reveals climate change is lifting South Africa out of the ocean

South Africa’s surface is rising. Slowly, almost invisibly, some areas are lifting by as much as two millimeters each year. Scientists long believed this was caused by forces deep beneath the Earth—hot plumes of mantle rock pushing upward over thousands of kilometers. But new research reveals a different, more immediate cause: drought.

Instead of heat from below, the Earth’s crust in parts of South Africa appears to be lifting due to water loss above. When surface and underground water vanish, the weight on the land decreases. That loss of pressure lets the land subtly spring upward, like a sponge expanding after being squeezed.

This groundbreaking conclusion comes from researchers at the University of Bonn, who analyzed satellite and climate data spanning nearly a decade.

Their results, published in the Journal of Geophysical Research: Solid Earth, could change the way scientists monitor and prepare for the effects of water loss in a warming world.

South Africa has an extensive system of Global Navigation Satellite System (GNSS) base stations called TrigNet. These were originally built to help with land surveying. However, they’ve become much more valuable to science than first imagined. For over 20 years, TrigNet has quietly been collecting precise data on land movement.

The vertical data from these stations show that land in many areas is rising. Between 2012 and 2020, researchers recorded an average uplift of six millimeters. Dr. Makan Karegar from the Institute of Geodesy and Geoinformation at the University of Bonn and his colleagues saw something unusual in the data. Uplift wasn’t random. It seemed to coincide with regions hit hardest by drought.

Up to now, the common explanation was the Quathlamba hotspot—a mantle plume, or a rising column of hot material from deep inside the Earth. Plumes like this can lift the surface slowly, over millions of years. That theory was supported by vertical movement patterns seen in GNSS data and comparisons to other hotspots like those under the Eifel volcanic fields in central Europe.

But those long-term trends didn’t explain the short-term shifts seen across South Africa. Karegar and his team suspected something else was going on.

To test their new idea, the researchers compared GPS station data with climate records and satellite measurements from the GRACE mission. These satellites measure changes in gravity caused by shifting masses, such as water loss from land.

What they found was striking. Where the GRACE satellites showed large drops in water mass—such as reductions in soil moisture, surface water, and groundwater—the GPS stations in those same areas showed the highest uplift. This wasn’t just a one-time coincidence. The pattern held across multiple years and across wide regions of the country.

Dr. Christian Mielke, a member of the research team, explained the power of GRACE data. Although these satellites can’t show detailed images like weather satellites, they do capture big-picture water trends. “These results can be used to calculate the change in the total mass of the water storage,” Mielke said.

The team didn’t stop there. They also used detailed hydrological models, which simulate how water moves through the ground, plants, and atmosphere. These computer models gave a much sharper view of drought impact. When combined with satellite and GPS data, the models confirmed that land uplift could mainly be explained by water loss, not mantle activity.

Think of the land like a foam ball pressed down by your hand. As long as your hand is there, the ball stays flattened. Remove your hand, and it slowly pops back up. The same thing happens to land when groundwater is removed. It rises. The Earth behaves elastically, reacting to changing loads on its surface.

This elasticity isn’t just a curious detail. It can be used as a tool. By measuring how much the land lifts during droughts, scientists can estimate how much water has been lost. That gives them an independent way to track water resources—especially underground reserves that are otherwise hard to see.

In a country like South Africa, where much of the water is stored in underground aquifers, this approach could be vital. As Karegar explained, “We believe that it’s also possible that a loss of groundwater and surface water is responsible for the land uplift.”

And the need for such monitoring tools is urgent. Between 2015 and 2019, Cape Town experienced a record-breaking drought. The threat of “Day Zero”—the day when the taps would run dry—became very real. The whole country was watching its reservoirs empty with growing alarm.

Even though TrigNet was built for mapping and engineering, scientists have been finding new uses for its data. The first studies used the network to monitor changes in the ionosphere and track atmospheric water vapor. Over time, researchers realized the system’s high-quality data was also suitable for crustal studies.

Although the South African landmass shows very little horizontal tectonic movement—it's part of the rigid Nubian plate—some vertical motion has caught geologists’ attention. Early observations linked this to mantle forces, but now it seems that nontectonic factors like drought may play a bigger role.

That’s not to say tectonics aren’t involved at all. Certain regions, especially those near gold mining zones and the eastern edge of the country, show higher earthquake risks. According to seismic hazard maps from Midzi and colleagues, these areas may still face geological threats. However, for most of the country, tectonic activity does not seem to drive the crustal uplift.

Instead, it’s the climate—specifically the drying of the land—that shapes the surface in the short term.

What makes this discovery so powerful is how little it costs. Unlike drilling wells or installing new sensors underground, GPS stations already exist and are collecting data 24/7. Scientists just needed to look at the vertical numbers in a new way.

This method could be used not only to detect drought, but to help manage water resources before they become dangerously low. If land starts to rise in a certain area, officials could take that as a warning sign and begin rationing water or strengthening conservation rules.

Over time, changes in vertical land motion could even be added to existing climate models. By tying together GPS data, satellite observations, and computer simulations, experts could gain a much clearer view of how climate change is affecting water reserves—not just in South Africa, but around the world.

As Mielke said, “This data also showed that the land uplift could primarily be explained by drought and the associated loss of water mass.” It’s a finding that reshapes how we see the ground beneath us—not as static and still, but as something responsive to how we treat our planet’s most precious resource.

The science is still evolving, but the message is clear. The Earth is speaking through tiny shifts in elevation. And what it’s saying is urgent: water is vanishing.

By studying this vertical movement, we now have a quiet but powerful way to monitor droughts. And thanks to tools like GPS and satellite data, scientists are listening closer than ever.

Note: The article above provided above by The Brighter Side of News.

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