Global warming may raise sea levels, flood coastal homes and drown low-lying islands beneath the Pacific’s waves. However, if we can tread water long enough, scientists say, eventually the world’s seas will fall again.
Australian and Norwegian researchers have produced the most detailed maps ever made charting the past and future changes to global ocean levels.
Thanks to the never-ending drift of the continents, sea levels are constantly fluctuating as oceans grow and shrink.
Dietmar Muller, an associate professor from the School of Geosciences at the University of Sydney, working with scientists from Norway’s Centre for Geodynamics, produced 141 maps showing sea-level changes at intervals of 1 million years.
About 140 million years ago, Professor Muller said, the sea “was maybe 100 metres higher than today. And 80 million years ago, it was 170 metres higher than today. There were huge inland seas in most continents”.
But the scientists also looked into the distant future when vast tracks of dry land will appear where today there is only water.
At first, climate change will raise ocean levels faster than continental drift can make them fall, Professor Muller said. “It is said that a rise of a metre would affect 60 million people world wide.”
As the continents slide further apart, however, ocean basins will grow larger, and undersea mountain ranges, created by hot buoyant rock beneath the sea floor, will sink, making oceans deeper.
As a result, in 80 million years, ocean levels will fall 120 metres and any global warming will make little difference.
“Even if all the ice in world melted, the sea level would still be 70 metres down,” he said.
The Gulf of Carpentaria will vanish. Indonesia’s thousands of islands will merge into one large land mass.
“Eventually the Atlantic and Indian oceans will grow and the Pacific shrink. One day the Pacific Ocean will probably disappear,” Professor Muller said.
“It is a powerful reminder that, unlike greenhouse gas emissions, we can’t control the planet’s geodynamics.”