A GEO Mountains Small Grant is helping researchers unlock a remarkable archive of historical aerial photographs, providing new insights into how glaciers in the Chilean Andes have changed over the last 80 years.
Glaciers are among the clearest indicators of climate change. Across the Andes, and particularly in Patagonia, glaciers are losing mass at an accelerating rate, with implications for water resources, ecosystems, hydropower production, and global sea-level rise. Yet despite their importance, scientists still know surprisingly little about how these glaciers have evolved over the past century.
One major reason is a lack of accessible historical data. While satellite imagery has transformed glacier monitoring since the early 2000s, understanding longer-term glacier change requires looking further back in time.
A GEO Mountains-supported project is helping to fill this gap by rescuing and digitising thousands of historical aerial photographs dating back to the 1940s, creating an unprecedented resource for glacier research in the Chilean Andes.
Rediscovering a Hidden Archive
The project, Unlocking Airborne Historical Stereo-Image Archives for Glacier Elevation Change Assessment in the Chilean Andes, focuses on a unique collection of aerial photographs captured during a United States Air Force survey in 1944–1945 using Trimetrogon cameras.
Although these images have existed for decades, they remained largely inaccessible for modern glacier research.
Working with the National Collection of Aerial Photography (NCAP), the U.S. National Archives and Records Administration (NARA), and Chilean partners, the research team digitised approximately 4,500 historical aerial photographs covering glaciers across Chilean Patagonia. This far exceeded the project’s original goal of around 350 images.
The team also acquired additional aerial photographs from the archives of the Chilean Air Force, providing valuable records from the 1980s and 1990s that help bridge the gap between historical imagery and modern satellite observations.
Turning Historic Photographs into 3D Glacier Records
Digitising historical photographs is only the first step. To understand how glaciers have changed, researchers need to transform pairs of overlapping images into detailed three-dimensional representations of the landscape.
To achieve this, the project developed a new open-source processing workflow capable of generating Digital Elevation Models (DEMs) from historical aerial imagery. These models allow researchers to reconstruct glacier surfaces from different points in time and measure how much ice has been lost.
Preliminary analyses have already been carried out for glaciers including Gran Campo Nevado and Grey Glacier, demonstrating the scientific potential of the approach. Once fully developed, the processing pipeline will allow researchers to build glacier elevation change records spanning nearly eight decades.
Building Tools and Capacity for Future Research
Beyond the historical image rescue itself, the project has contributed to broader efforts to improve access to glacier data and methods.
Researchers co-organised and supported an international workshop in Grenoble, France, bringing together experts and early-career researchers working on historical image processing. The workshop forms part of the international Historix initiative, which compares different approaches for reconstructing topography from archival imagery.
The project has also prioritised open science by developing an open-source processing pipeline that can be used and adapted by researchers worldwide.
“The GEO Mountain Small Grant has helped us unlock a unique archive of historical airborne photographs taken over the Chilean Andes in the 1940s,” says project lead Livia Piermattei, a professor at the University of Zurich. “This archive allows us to quantify long-term glacier elevation changes by combining these images with other historical aerial photos and modern remote sensing data. In addition to the scientific value of scanning and preserving this unique dataset, the project provides open-source tools and shared expertise, enabling other researchers to work with historical aerial imagery.”
Looking Ahead
Although work is still ongoing, the project has already laid the foundations for a much richer understanding of glacier change in Patagonia.
The next steps include finalising and publishing the open-source processing workflow, producing long-term glacier elevation change records for key Patagonian glaciers, and creating a public database to make the elevation models and derived glacier products accessible to the wider scientific community.
The team also hopes to expand this work beyond Patagonia and unlock similar historical archives from other glacierised regions around the world.
By transforming forgotten aerial photographs into valuable scientific data, this project demonstrates how historical records can help answer some of today’s most pressing climate questions.