Antarctic Ice Shelves Melt From Warmer Ocean Below: Surprising New NASA Research

A new study has found that most of Antarctica's ice shelves melt from the bottom up. Basal melting from the warmer ocean underneath accounts for much more ice loss than previously thought.

Before this study, scientists thought that most of Antarctica's ice shelf loss was the result of icebergs splitting apart and falling into the sea. This process is called calving. Now, however, they've realized that calving is not the full picture. The warmer ocean melting ice from underneath, or basal melt, is largely to blame.

The study's data was from ice thickness data compiled by NASA's Operation Ice Bridge, which used satellites, aircraft, radio echo sounding and other methods to survey ice cover on both of Earth's poles over six years. Ice shelves are

"We find that iceberg calving is not the dominant process of ice removal. In fact, ice shelves mostly melt from the bottom before they even form icebergs," said the study's lead author, Eric Rignot, in a press release. "This has profound implications for our understanding of interactions between Antarctica and climate change. It basically puts the Southern Ocean up front as the most significant control on the evolution of the polar ice sheet."

Ice shelves are permanent sheets of floating ice that cling to land masses found mostly in the Antarctic. They're attached to 44 percent of the Antarctic coastline and are formed as ice from the land flows out to the sea and as snow falls on the ice.

Antarctica holds about 60% of the planet's fresh water, and as icebergs melt, sea levels rise.

Dr. Rignot, a professor at University of California, Irvine, who also works at NASA's Jet Propulsion Laboratory in Pasadena, conducted the study.

"Ice shelf melt can be compensated by ice flow from the continent," Rignot said. "But in a number of places around Antarctica, they are melting too fast, and as a consequence, glaciers and the entire continent are changing."

Only a few smaller ice sheets were responsible for over half the melt. Antarctica's largest ice sheets, Ross, Filchner, and Ronne, which make up two-thirds of Antarctica's shelves, were behind just 15 percent of the ice melt.