While researchers are still learning new things about the complex ways ice melts at the Thwaite Glacier, at its most basic, the giant cavity represents a simple (if unfortunate) scientific actuality.
But they were shocked to find the hole and then "surprised" to see its "size and explosive growth rate".
NASA believes the cavity is big enough to have contained 14billion tons of ice, most of which melted only in the last three years.
As reported in the journal Science Advances, researchers have gained a clearer picture of the glacier's plight.
Scientists spotted the concealed void thanks to a new generation of satellites, Rignot noted.
The agency's Jet Propulsion Laboratory used ice-penetrating radar to explore the area beneath the Thwaites Glacier in West Antarctica, often called "one of the world's most risky glaciers" because its melting could significantly contribute to sea level rise.
By observing the undersides of Antarctic glaciers, researchers hope to calculate how fast global sea levels will rise in response to climate change. The growing cavity is the red mass at the center. The mottled area (bottom left) shows extensive iceberg calving. The new discovery implies that this limitation most likely causes those models to underestimate how fast Thwaites is losing ice.
Once gone, surrounding glaciers will have no obstacle in their path, speeding up their melting and the potential release of enough water to raise sea levels by as much as 2.4m.
Thwaites Glacier is about the size of Florida and now responsible for roughly 4 percent of global sea rise.
The US National Science Foundation and British National Environmental Research Council are beginning a five-year field project to answer the most critical questions about its processes and features.
While Thwaites is certainly a hard place to reach, a five-year expedition by the International Thwaites Glacier Collaboration to study the glacier will begin this summer.
Instead, the team used airborne and satellite ice-penetrating radars to reveal the cavity. Many Antarctic glaciers extend for miles beyond their grounding lines, floating out over the open ocean. When this happens, the grounding line retreats inland.
"We are discovering different mechanisms of retreat, ' Mr Milillo said". Scientists have long thought that the glacier was not attached firmly to the bedrock beneath it. On top of the usual story of thinning ice, they found a enormous cavity - perhaps the size of the Eiffel Tower - growing at the bottom of the vast glacier. The glacier has retreated at a steady rate of about 0.4 to 0.5 miles (0.6 to 0.8 km) annually since 1992, the researchers found.
Despite this stable rate of grounding-line retreat, the melting rate on this side of the glacier is extremely high.
The glacier isn't retreating uniformly. Hopefully, the upcoming worldwide collaboration will help researchers piece together the different systems at work under and around the glacier, the researchers said.