Sea levels might rise or fall if warming continues

The new evidence unearthed by the Woods Hole Oceanographic Institution is based on sea level changes during a warm period about 125,000 years ago, known as the Last Interglacial.

"This was the last time that the climate was as warm as -- or warmer than -- today," said WHOI geochronologist William G. Thompson, who led the study, the journal Nature Geoscience reports.

Sea levels during the Last Interglacial are known to have been about six metres (20 feet) higher, on average, than they are today.

"The real surprise is that sea levels were oscillating during this period," said Thompson, according to a Woods Hole statement.

"If today's ice sheets continue to melt, we may be headed for a period of ice sheet and sea-level change that is more dynamic than current observations of ice sheets suggest," added Thompson.

The polar ice caps currently are shrinking and sea level is rising at a rate of about 30 cm (one foot) per century.

"How much sea level will rise over the next century or two is a crucial question for the significant part of the world's population that lives in coastal zones," Thompson said.