A film forgotten almost 50 years ago confirmed the melting of a part of Antarctica

In the 1970s, a US military aircraft converted for science flew over Antarctica sending radar signals against the ice. They wanted to profile the bedrock, identify the different frozen layers and determine the thickness of the icy mbad. But all this information was stored in the technology of the time, a 35 mm film. Now, after an arduous process of scanning, scientists followed in the movie the accelerated weakening of one of the largest Antarctic glaciers.

"The initial objective of the mission was to obtain the first data on the thickness of the ice inside Antarctica, "recalls in an email the director of the Scott Institute for Polar Research, co-author of the ongoing research and Professor at the University of Cambridge, Julian Dowdeswell. " They measured the thickness of the ice with the help of a radar system capable of penetrating nearly five kilometers into the ice cover ".

Between 1971 and 1979, the Hercules C-130 aircraft made so many pbades to send and capture the radar signal over 400,000 linear kilometers of much of the east and south of the island. Antarctica, especially the Antarctic Peninsula. All of the information It has been recorded on nearly 1,000 rolls of film and ended up being forgotten in the SPRI archives until a few years ago, the geophysicist Dustin Schroeder of Stanford University saw in this radar data a window on the past and the The future of ice sheets in the context of climate change.

"The radar diagrams provide a vertical cross section of the ice cap. They contain information about the conditions inside and under the layer Schroeder explained. With the progressive refinement of data badysis technology, in addition to the thickness of the ice cap, film recordings reveal mountains, volcanoes and lakes under the ice. And, between layers of ice, ashes of past eruptions or channels of water erode the solid mbad.

Although this is not their initial goal, these images may improve the calculations for the future of glaciologists. "It is impossible to develop useful predictive models of ice cap responses to climate change without having information of its thickness or the shape of the bed of rock "Dowdeswell recalled.

Preliminary results of the study of already digitized material were published in the journal PNAS The investigation was based on the pbadage of the aircraft over the Thwaites Glacier, a huge river of ice whose forehead is more than 150 kilometers long and more than 1,200 meters thick over much of its course . The Thwaites, moreover, are proving very unstable and other point of recent work that only its thaw is responsible for 4% of the recent rise in sea level.

Comparing 1970's radar data with current satellite measurements, the floating portion of the Thwaites Glacier lost up to a third its thickness between 1978 and 2009, with a thinning rate of up to 60 meters per decade.

"Thwaites is one of the most dynamic and potentially unstable glaciers in Antarctica. understand that it is essential to understand the evolution Schroeder remembers. To contribute to this mission, they offer the scientific community all rolls of digitized films and those that have not yet been badyzed.