Washington, March 7 : A new study of 80 millions years ago, has suggested that global sea levels were roughly 560 feet (170 meters) higher than they are today and might plunge downwards in the future.
Geologists from the University of Sydney in Australia conducted the study.
According to a report in National Geographic News, if sea levels were that high now, vast regions would be flooded: most of northern Europe, large sections of South America, the East Coast of North America, and parts of Australia.
The finding stems from more than a decade of effort to virtually reconstruct ancient ocean basins to understand how their size and depth have changed since the Cretaceous, which lasted from 145.5 to 65.5 million years ago.
The result is a dramatic image of historic sea level change that goes beyond what is expected in the coming decades due to rapid global warming-induced ice cap melting.
"They are natural processes that also contribute to sea level change and are in fact independent of ice cap melting," said Dietmar M¼ller, a geologist at the University of Sydney in Australia.
"In fact, the data reveal that the long-term trend in sea levels since the Cretaceous has been downward," said M¼ller.
The team found that, during the late Cretaceous, huge mid-ocean ridges wrapped around the planet, making the global ocean much shallower on average than it is today.
"In particular, a mid-ocean ridge system in an ancient ocean called Panthalassa-the precursor to the Pacific-was a crucial force driving sea level change through time," said M¼ller.
Much of that system no longer exists, which largely explains why sea levels have fallen over the last 80 million years.
When this trend is extrapolated out 80 million years from now, it suggests that even if all of today's ice caps were to melt, sea levels would be 230 feet (70 meters) lower than they are today.
Pictured on today's globe, that much of a sea level drop would mean that Indonesia would be largely connected to mainland Southeast Asia.
Furthermore, all the continents would be larger, so today's coastal cities would be stranded inland. Going forward, the researchers' model suggests that the Atlantic Ocean will continue to grow and the Pacific Ocean will shrink as more mid-ocean ridges disappear.
"As time goes by, we will therefore increase the volume of the ocean basins because it will become deeper than average, so this will result in a long-term sea level drop," said M¼ller.