Presented at a meeting of Internet network researchers on Monday, the study, which only considered risk to infrastructure in the US, looked at critical communications infrastructure that could be submerged by rising seas, the website phys.org said.
The senior author of the study, Paul Barford, a professor of computer science at the University of Wisconsin-Madison, said: "Most of the damage that's going to be done in the next 100 years will be done sooner than later.
"That surprised us. The expectation was that we'd have 50 years to plan for it. We don't have 50 years."
The study suggests that by the year 2033, about 2500 kms of buried fibre optic conduit will be underwater and over 1100 traffic hubs will be surrounded by water.
At most risk are New York, Miami and Seattle, Barford warned, adding that the effects would not be limited to these cities and the inundation had the potential to disrupt global communications.
Barford is considered an authority on the physical Internet - the buried fibre optic cables, data centres, traffic exchanges and termination points that are the nerve centres, arteries and hubs of the Internet.
Most of this infrastructure is buried and often runs parallel to highways and coastlines.
Barford said: ""The first instinct will be to harden the infrastructure. But keeping the sea at bay is hard. We can probably buy a little time, but in the long run it's just not going to be effective."