By Matt Rocheleau, Globe Staff
Concerned by a new study this week that found the world’s oceans rose significantly faster last century than in any of the previous 27 centuries?
You might be even more troubled to know that the same report says levels along the East Coast, including Massachusetts’ shores, increased even faster during the 20th century – and researchers expect those trends will continue.
“There are reasons to think Boston and other areas of New England and along the East Coast will continue to see greater relative sea level rise than the global average,” said Andrew Kemp, an assistant professor in Tufts University’s Department of Earth and Ocean Sciences.
“We know there are a lot of processes that are going to make it a lot worse here than other parts of the world,” he added.
Kemp and another area researcher, Jeffrey Donnelly of the Woods Hole Oceanographic Institution, in recent years helped study and collect data about how sea levels have risen along the shores of Massachusetts and Connecticut.
Their analysis, along with research by another local scientist, Harvard geophysics professor Jerry Mitrovica, was included in a study published Monday in the Proceedings of the National Academy of Sciences.
That new study, which made headlines this week, calculated that the global sea level rose by about 5.4 inches between 1900 and 2000.
At three sites where data has been tracked in Massachusetts, the rise was higher.
In Barnstable, there was an 11.1-inch increase in sea levels last century, the study found. In Revere, the water rose 9.3 inches. At Wood Island, it increased by 8.8 inches.
Three other sites in Connecticut all saw sea levels rise by more than 10 inches.
The largest increase was 15.2 inches at a spot in New Jersey. Other parts of the Garden State as well as spots in North Carolina also saw increases larger than the global number.
The findings are similar to previous research that has found sea levels to be rising faster along the East Coast than in other parts of the planet.
So why has the ocean swallowed more of the shorelines here?
“The ocean isn’t a bathtub; it doesn’t rise equally everywhere,” Kemp explained.
One key factor is that we’re sinking.
“On the East Coast of the US, the biggest change [until about 1850] was that the land was going down rather than the sea going up,” said Kemp.
He explained that the massive sheet of ice that covered Canada during the Ice Age was so heavy that it caused the land below it to be pushed downward, which triggered land to rise in other areas, including New England.
As ice from the Ice Age melted, it triggered a reversal of that process, and it’s still not done. Kemp said land here is still sinking at a rate of about 1 millimeter annually and we can expect that to continue for at least the next 1,000 years.
“The process goes on for thousands of years even after the ice melts away,” he said.
Other phenomena responsible for why relative sea levels have risen faster here than in other parts of the world include changes in the Gulf Stream current in the Atlantic Ocean and melting ice at the top of the world, he said.
Even though much of that ice melting is happening in relatively far away places like Greenland, it causes sea levels to rise faster here.
“Boston has a lot more to fear than Greenland, which of course is counterintuitive,” said Kemp, pausing.
The study released this week – which was largely in line with other recent studies on the topic – also projected that by 2100 global sea levels will rise by anywhere from another 11 inches to another 4 feet 4 inches, depending on how much greenhouse gas emissions can be reduced.
Scientists say the rising sea levels will have a major impact on coastal communities.