The reports represent the crossing of a “critical threshold” in understanding Antarctic ice sheets, said researchers at NASA and the University of California at Irvine who were behind the studies, scheduled for publication this week in the journals Science and Geophysical Letters.

Conclusions in the reports are based on 40 years of observation of the rapidly melting Amundsen Sea area of West Antarctica. Six glaciers in the region have entered an “unstoppable” retreat that has “passed the point of no return,” the researchers said.

“It has been compared to a wine bottle that has a cork at the front, where the cork represents the ice shelf,” said Eric Rignot, a professor of earth system science at the UC Irvine and a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

“We’re at the point where we can say the bottle has been uncorked,” he said at a news conference Monday.

The scientists said they called the glacial retreat “unstoppable” because they now know from on-the-ground observations that the topography of the land under the glaciers will do nothing to stop the melting.

Researchers said a hill or a mountain would be necessary to recork the bottle, but their studies show there are no such formations. Instead, the ground drops off, putting the glaciers even farther below sea level and exposing more of the ice to warming waters, which could accelerate their retreat.

West Antarctic glaciers sit on land largely below sea level, unlike those in the eastern part of the continent, making them more susceptible to melting from the warming temperatures of the ocean.

The melting of West Antarctic glaciers could have major consequences worldwide, the scientists said, and could result in an additional 1.2 meters, or about four feet, of sea level rise (SLR) in addition to what had already been predicted in other studies, like the IPCC report.

“This part of Antarctica is undergoing enormous change,” Sridhar Anandakrishnan, a professor of geosciences at Pennsylvania State University at University Park, said at the news conference Monday.

Warming ocean temperatures — as opposed to air temperatures — are driving the irreversible retreat of the West Antarctic glaciers, the reports said.

“It is the temperature of the water that is in this case eating away at the glaciers’ feet” and causing their retreat, Anandakrishnan said.

Warming waters are pulled toward the poles by wind patterns that scientists said have been strengthening over the past two decades. Depletion of the ozone layer over Antarctica also contributes to accelerated melting, the reports said.

It is becoming clear that Antarctic ice will have a larger role in SLR in the decades ahead, the scientists said. Previous SLR estimates have not taken into account Antarctic melting because of lack of data.

“Predictions of SLR will have to change upwards because of this,” Anandakrishnan said, adding that the redistribution of West Antarctic glacial mass could have worldwide implications. “People don’t realize how big these critters are,” he said.