New analysis of gravity data, along with bed topography and ice thickness observations, has revealed the presence of large seafloor valleys hiding beneath the glaciers of West Antarctica.

The valleys were carved by the advance and retreat of glaciers during much colder periods of Earth's climate history. Today, they provide a tunnel through which warm ocean currents can access the underside of glaciers flowing into the the Amundsen Sea.

"These oceanic features are several hundreds to a thousand meters deeper than what we thought before," Romain Millan, a graduate student at the University of California, Irvine, said in a news release. "It gives new insight into the future fate of these glaciers and the potential influence of warm ocean water that can melt away ice from below."

Between 2009 and 2014, NASA's Operation IceBridge missions measured slight variations in Earth's gravity during aerial surveys of Antarctica. Researchers used the data, along with previous bed topography maps and ice thickness measurements, to generate improved models of the seafloor beneath West Antarctica.

The models revealed depressions beneath both Pine Island Glacier and Thwaites Glacier. Even larger submarine valleys were found under the Crosson and Dotson ice shelves.

"Based on our research, we now have a much clearer picture of what is hiding under these large glaciers located in a particularly vulnerable sector of West Antarctica," Millan said.

Scientists detailed their discovery in the journal Geophysical research Letters.

Understanding how changes in the ocean can affect glaciers in Antarctica is essential to the task of building more accurate climate models and predicting sea level rise.

Current models suggest the collapse of the Amundsen Sea Embayment -- one of three major ice drainage basins making up the West Antarctic Ice Sheet -- will lead to a four-foot rise in sea levels.

While the newly discovered channels offer access to the underside of vulnerable glaciers, models also revealed the presence of a deep sill which may block the access of the warmest ocean waters.

"This is good news in terms of having these glaciers not fully exposed, but it makes the projections more challenging because all tiny details will be important in controlling ocean heat access to the glaciers," said Eric Rignot, an Earth system science professor at UCI.