Challenging modern climate stories: Forgotten aerial photographs from 1937 expose the Antarctic anomaly

A study using forgotten aerial photographs taken by a whaling ship from 1937 shows that the ice in East Antarctica has remained stable and even grown, despite some early signs of weakening.

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

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

“We constantly hear about climate change and new melt records, so it is refreshing to observe an area of ​​glaciers that have remained stable for almost a century,” says PhD student Mads Dømgaard, the 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 around the glaciers, suggesting that these stable East Antarctic glaciers could shrink in the future.

“Our results also indicate a weakening sea ice state, making the glaciers’ floating ice tongues more vulnerable and unable to grow as large as seen in early aerial photographs 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 in West Antarctica, for example,” says Dømgaard.

Hidden from the Nazis

Most of the images used in the study were taken 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 due to the German invasion of Norway the maps were never published. 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 likely hidden in an archive in Norway. They traveled to Tromsø and viewed all 2,200 photos taken during the expedition. They supplemented the Norwegian aerial images with images of the same glaciers from Australian surveys conducted between 1950 and 1974.

“By comparing the historic aerial photographs with modern satellite data, we have gained critical knowledge about glaciers that we would not have had otherwise. 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 with the historic 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 because they give us a unique insight into how the ice has developed through a changing climate and whether current changes in the ice exceed the normal cycle of glacier advance and retreat,” Dømgaard explains.

Improving predictive models

According to the researcher, solid long-term data are crucial for making accurate predictions of future glacier revolutions and sea level rise, and this study provides new insights into a vast area of ​​East Antarctica.

“The long time series of glaciers improve our ability to create more accurate models of future ice changes, because the models are trained on historical observations,” Bjørk concludes.

The findings were recently published in Nature communicationthe result of a joint effort between researchers from the University of Copenhagen, the Norwegian Polar Institute, the Arctic University of Norway and the Institute for Environmental Geosciences in France.

More about the study

• Of the 2,200 images photographed from seaplanes in 1937, 130 were selected for analysis.
• The researchers combined the historic 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 conducted between 1950 and 1974. This allowed the researchers to investigate the evolution of the glaciers over different periods and calculate historical ice flow rates for selected glaciers.
• Compared to modern data, ice flow rates are unchanged. Although some glaciers have thinned over shorter intervals of ten to twenty years, they have remained stable or grown slightly in the long term, indicating that the system is in equilibrium.

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

The research was funded by the Villum Foundation.