Forgotten aerial photos from 1937 expose the Antarctic anomaly

A study using long-forgotten aerial photographs of a whaler from 1937 shows that East Antarctic ice has been stable and even growing, despite some early signs of weakening.

Extreme weather, melting glaciers and rising sea levels are all indications that the world’s climate and ice masses are in critical condition. However, a new study from the Department of Geosciences and Natural Resource Management at the University of Copenhagen reveals a positive anomaly.

Using hundreds of old aerial photographs dating back to 1937, combined with modern computer technology, researchers have tracked the evolution of glaciers in East Antarctica. This area, which includes approximately 2,000 kilometers of coastline, contains as much ice as the entire Greenland ice sheet. By comparing historic aerial photos with modern satellite data, the researchers determined the glacier’s movement and changes in size, revealing that the ice has not only remained stable, but has also grown slightly over the past 85 years, in part due to increased snowfall.

“We constantly hear about climate change and new melting records, so it’s refreshing to observe a glacier area that has remained stable for almost a century,” says PhD student Mads Dømgaard, first author of the study.

Early signs of change

Despite the overall stability, the research also reveals the first signs of changes in the sea ice surrounding the glaciers, indicating that these stable East Antarctic glaciers may shrink in the future.

“Our results also show weakening sea ice conditions, making floating glacier ice tongues more vulnerable and unable to grow as large as seen in early aerial images from 1937. We know from other parts of Antarctica that the ocean plays an extremely important role and drives the massive and increasing melting we see e.g. in West Antarctica,” says Dømgaard.

Hiding from the Nazis

Most of the images used in the study were captured during a 1937 expedition organized and paid for by Norwegian whaler Lars Christensen. The mission aimed to produce the first maps of this part of East Antarctica, but the maps were never published due to the German occupation of Norway. Since then, the images have been stored at the Norwegian Polar Institute in Tromsø and forgotten.

When researchers from the University of Copenhagen read about the expedition, they realized that valuable images were hidden in an archive in Norway. They traveled to Tromsø and reviewed all 2,200 images taken during the expedition. They supplemented the Norwegian aerial images with images of the same glaciers from Australian surveys carried out between 1950 and 1974.

“By comparing historic aerial photos with modern satellite data, we have gained critical insights into glaciers that we would not otherwise have. I think it’s fantastic that these old images can be used to generate new research results almost 100 years after they were taken,” says Assistant Professor Anders Bjørk from the University of Copenhagen, who leads the group working on the historical images.

Potential for rapid sea level rise

The Antarctic ice sheet is receiving increasing attention from researchers because of its potential for extremely large and rapid sea-level rise. Unlike Greenland, very little was known about Antarctica’s glaciers until the 1990s, when the first good satellite observations became available.

“Early observations of glaciers are extremely valuable as they give us a unique insight into how the ice has evolved through a different climate and whether current changes in the ice exceed the normal cycle of glacier advance and retreat,” explains Dømgaard.

Improving Predictive Models

According to the researcher, stable and long-term data are essential for producing accurate predictions of future glacier evolution and sea level rise, and this study provides new insights into a wide area in East Antarctica.

“The long glacier time series improves our ability to make more accurate models of future ice changes, as the models are trained on historical observations,” Bjørk concludes.

The findings were recently published in Nature Communicationsresulting from a collaborative effort involving researchers from the University of Copenhagen, the Norwegian Polar Institute, the Arctic University of Norway and the Institute of Environmental Geosciences in France.

More about the study

• Of the 2,200 images photographed by seaplanes in 1937, 130 were selected for analysis.
• The researchers combined historical photos with modern satellite data to create 3D reconstructions of the glaciers.
• The Norwegian aerial images were supplemented with 165 aerial images of the same glaciers from Australian surveys carried out between 1950 and 1974. This allowed the researchers to examine the evolution of the glaciers over different periods and to calculate historical ice flow velocities for the selected glaciers .
• Compared to modern records, ice flow velocities are unchanged. While some glaciers have thinned over shorter intervening periods of 10–20 years, they have remained stable or grown slightly over the long term, indicating a system in equilibrium.

Reference: “Early aerial expedition photos reveal 85 years of ice growth and stability in East Antarctica” by Mads Dømgaard, Anders Schomacker, Elisabeth Isaksson, Romain Millan, Flora Huiban, Amaury Dehecq, Amanda Fleischer, Geir Moholdt, Jonas KA Bjørk, May 25, 2024, Nature Communications.
DOI: 10.1038/s41467-024-48886-x

The research was funded by the Villum Foundation.