chance discovery of 80-year-old photo plates in a Danish basement is providing vital new clues into how Greenland glaciers are melting today. Researchers at the National Survey and Cadastre of Denmark - that country\'s federal agency responsible for surveys and mapping - had been storing the glass plates since explorer Knud Rasmussen\'s expedition to the southeast coast of Greenland in the early 1930s. In this week\'s online edition of Nature Geoscience, Ohio State University researchers and colleagues in Denmark describe how they analyzed ice loss in the region by comparing the images on the plates to aerial photographs and satellite images taken from World War II to today. Taken together, the imagery shows that glaciers in the region were melting even faster in the 1930s than they are today, said Jason Box, associate professor of geography and researcher at the Byrd Polar Research Center at Ohio State. A brief cooling period starting in the mid-20th century allowed new ice to form, and then the melting began to accelerate again in the 2000s. \"Because of this study, we now have a detailed historical analogue for more recent glacier loss,\" Box said. \"And we\'ve confirmed that glaciers are very sensitive indicators of climate.\" Pre-satellite observations of Greenland glaciers are rare. Anders Anker Bjørk, doctoral fellow at the Natural History Museum of Denmark and lead author of the study, is trying to compile all such imagery. He found a clue in the archives of The Arctic Institute in Copenhagen in 2011. \"We found flight journals for some old planes, and in them was a reference to National Survey and Cadastre of Denmark,\" Bjørk said. Hiker gazing at melting Greenland Glacier, via Shutterstock.