The rapid structural breakdown of some important parts of the ice sheets on Greenland and Antarctica is possible, has happened in the distant past, and some "startling changes" on the margin of these ice masses has been observed in recent years – raising disturbing concerns about sea level rise.In a new report to be released Friday in the journal Science, researchers from Oregon State University and four other institutions in the U.S. and Europe outline dynamic mechanisms of glacial change that appear to be under way, could significantly speed up the melting of major ice sheets, and have not been considered in current projections for sea level rise.
A possibility, scientists say, is that the melting and collapse of floating ice shelves near the coasts of Greenland and Antarctica will continue and in the process destabilize the ice sheets behind them.
This could cause a much more rapid flow of ice to the sea and lead to melting events that transcend those now anticipated due to global warming. Based on this, the researchers say that current projections of sea level rise should be considered a minimum to expect, and the levels could be much higher and happen more quickly.
"Most of the sea level rise we're now expecting in the next 200 years is due to thermal expansion of water, not the overall loss of ice from Greenland and Antarctica," said Peter Clark, a professor of geosciences at OSU. "But recent events we've studied with improved observational systems and computer modeling suggest there may be much more going on."
"We may be more vulnerable to sea level rise than we thought and it may be more rapid than we have anticipated," Clark said. "This is an issue we should take very seriously."
Although they are learning a great deal more about the mechanisms that may lead to more rapid glacial collapse, the scientists cannot yet predict with certainty whether or how fast it might happen, or what the resulting sea level rise may be.
In one event about 14,600 years ago, Earth's sea level rose about 70 feet in less than 500 years – 20 times faster than the current rate of sea level rise. However, climatic conditions then may have been considerably different than today, and that event may not provide an exact analog to what we might expect from current glacial melting events, Clark said. Nevertheless, that event illustrates the potential for existing ice sheets to cause sea level to rise rapidly, he said.
*gulp*