The latest, published Thursday in the scientific journal Nature
, says melting ice in Antarctica has the potential to contribute to a rise in sea levels of 1 meter -- more than 3 feet -- by the end of this century.
And it says with ice also melting in other parts of the world, seas could rise 5 or 6 feet by the end of this century, far more than predicted in a 2013 United Nations study.
"We're looking at the potential for a rate of sea level rise that we will be measuring in centimeters (rather than milliliters) per year -- literally an order of magnitude faster," said Robert DeConto of the University of Massachusetts Amherst, one of the study's authors.
"Can we build walls and levies and dikes fast enough to keep up with that? One concern would be that at that point you're sort of looking at managed retreat essentially, rather than geoengineering in a lot of places."
The study, by DeConto and David Pollard of Pennsylvania State University, says by 2500, Antarctica could contribute to a rise in sea levels of 15 meters, or nearly 50 feet.
"At the high end, the worst-case scenarios, with sort of business as usual greenhouse gas emissions ... we will literally be remapping coastlines," DeConto told CNN.
And by the middle of the next century, seas could be rising at a rate of more than 1 foot per decade if the emission of greenhouse gases continues unchanged, the study says.
"North America is kind of a bull's eye for impacts of sea level rise if it's the west Antarctic part of Antarctica that loses the ice first," DeConto said. "That's the place that we're worried about losing ice first."
In September, NASA said the world was locked into a rise of sea levels of at least 3 feet, if not more
, surpassing projections from a few years earlier.
"Even if their dire predictions are cut in, let's say, half, we are still going to have serious problems in coastal cities," Carlos Del Castillo, chief of NASA's Ocean Ecology Laboratory, said of the latest research. "Sea level rise is not getting the attention it deserves. It has clear and serious implications to our way of life."
He added, "In this country we benefited and are very proud of the decisions made by our forefathers and mothers. The question that we and our brave politicians and policy makers have to ask is, if future generations are going to be equally proud of us. I think not."
DeConto predicts an industry boom in demolition and rebuilding on higher ground.
But there is still time to start curtailing greenhouse gas emissions, he said.
"That's the good news in this story," DeConto said. "This study is suggesting the worst-case scenario might be worse than we were thinking a few years ago, but it still highlights that policy is going to play a really big role in which future path we go down in terms of sea level rise. The horse isn't completely out of the barn yet."
The new study comes on the heels of another, done by the National Snow and Ice Data Center
, which also concluded that melting ice in the Antarctic poses a serious problem.