This means small tsunamis that might not be deadly today could wreak havoc in the future.
“Our research shows that sea-level rise can significantly increase the tsunami hazard, which means that smaller tsunamis in the future can have the same adverse impacts as big tsunamis would today,” said Robert Weiss, a professor of geosciences at Virginia Tech.
Weiss worked with the Earth Observatory of Singapore, the Nanyang Technological University and the National Taiwan University to map the dangers of future tsunamis.
He explained that small tsunamis generated by earthquakes occur frequently around the world, and may eventually be far more hazardous.
The researchers created computer-simulated tsunamis at current sea levels and then compared them to the same simulations with sea-level increases of 1.5 feet and 3 feet.
Weiss’ simulations charted the effect of a tsunami in Macau, a densely populated region in southern China.
The area is generally considered safe from the threat of tsunamis. At current sea levels, an earthquake would need to measure a magnitude of 8.8 or higher to cause “widespread tsunami inundation” in Macau.
But with a sea-level rise of 1.5 feet, the frequency of tsunami-induced flooding in the simulation rose by 2.4 times.
And for the 3-foot increase, the frequency of flooding rose to 4.7 times.
“We found that the increased inundation frequency was contributed by earthquakes of smaller magnitudes, which posed no threat at current sea level, but could cause significant inundation at higher sea-level conditions,” said Lin Lin Li, a senior research fellow at the Earth Observatory of Singapore.
Scientists used 5,000 tsunami simulations generated from “synthetic earthquakes” in the Manila Trench.
The Manila Trench is the main hazard point for large tsunamis in the South China Sea.
It hasn’t experienced an earthquake larger than magnitude 7.8 since the 16th century.
But study co-author Wang Yu said that the region shares many similarities to the source areas that led to the deadly 2004 Indonesian earthquake and Japan’s 2011 quake – both of which led to huge tsunamis.
In the future, it’s possible that smaller-magnitude earthquakes could instigate similar events – all thanks to rising sea levels.
It’s estimated that sea levels in the Macau region will increase by 1.5 feet by 2060, and by 3 feet by 2100.
“The South China Sea is an excellent starting point for such a study because it is an ocean with rapid sea-level rise and also the location of many mega cities with significant worldwide consequences if impacted,” explained Weiss.
“Sea-level rise needs to be taken into account for planning purposes, for example for reclamation efforts but also for designing protective measures, such as seawalls or green infrastructure.”
He went on: “What we assumed to be the absolute worst case a few years ago now appears to be modest for what is predicted in some locations.
“We need to study local sea-level change more comprehensively in order to create better predictive models that help to make investments in infrastructure that are or near sustainable.”
Sea levels aren’t just rising in the South China Sea – they’re rising globally.
The rise is largely attributed to global climate change: partly due to warming seas, causing “thermal expansion” of the water, and partly due to melting ice sheets and glaciers on land.
It’s estimated that we’ll see a rise of between 1 and 8 feet during the 21st century.
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