Rising sea levels have disturbed the skeletons of soldiers killed on the Marshall Islands during World War Two.
Speaking at UN climate talks in Bonn, the Island's foreign minister said that high tides had exposed one grave with 26 dead.
The minister said the bones were most likely those of Japanese troops.
Driven by global warming, waters in this part of the Pacific have risen faster than the global average.
With a high point just two metres above the waters, the Marshall Islands are one of the most vulnerable locations to changes in sea level.
The 29 atolls that make up the Marshall Islands are home to around 70,000 people. The corals that have formed the island chain are highly vulnerable to the surrounding seas.
Now the waters are posing a new, macabre challenge.
"These last spring tides in February to April this year have caused not just inundation and flooding of communities but have also undermined regular land, so that even the dead are affected," said foreign minister Tony De Brum, speaking on the sidelines of the UN climate negotiations.
"There are coffins and dead people being washed away from graves, it's that serious."
He gave details of an island in his constituency where a mass grave with 26 bodies had been exposed.
"We think they are Japanese soldiers, no broken bones, no indication of war, we think maybe suicide," he said.
The Islands were occupied by the Japanese during World War Two, until they were driven out by US forces.
In the years that followed the Islands were subject to dozens of nuclear weapons tests.
Now, according to their political leaders, they face an existential threat from global warming that is expanding the seas that surround them.
According to a recent report from the UN Environment Programme, sea level is rising in the Pacific around the Marshall's at a much higher rate than elsewhere in the world. The rate of rise between 1993 and 2009 was 12mm per year, compared with the global average of 3.2mm.
Mr De Brum urged his fellow ministers attending these talks to "commit to commit" on the issue of curbing carbon emissions.
The negotiators here are trying to develop a negotiating text that will form the basis of a new global treaty to be signed next year.
However there are still formidable challenges.
Ministers are aiming to publish their commitments to cut carbon by the spring of 2015 at the latest, but they have still not agreed on what should be included in these so-called nationally determined contributions (NDCs).
They have another opportunity to get it done, at a critical meeting in Peru in December.
"The NDCs are a very key element in the negotiation," said Manuel Pulgar-Vidal, who remains confident that a deal can be done. But everything, he says, needs to speed up.
"People, I'm sure are recognising that Lima is the last opportunity, to have something strong to move towards Paris to have an agreement."
A continuing problem is the question of how much responsibility for cutting emissions should rest on the shoulders of the emerging economies.
China, India and others are keen to stick to the UN formula of "common but differentiated responsibilities" meaning that the richer nations do most of the heavy lifting.
But the developed countries want to change this to take account of economic development.
Speaking in Bonn, EU climate commissioner Connie Hedegaard said these talks cannot continue with an interpretation that reflects the last century and not this one.
"We cannot continue with the old firewall thinking to be blunt. This is not a static thing. One country's fair share must also depend on where they are in terms of economic development."
Solving this issue will be key to any form of agreement that emerges from this process.