Forgotten aerial photographs from 1937 reveal an Antarctic anomaly

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

Extreme weather, melting glaciers and rising sea levels are all indicators that the climate and the world’s ice mass 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 from 1937, combined with modern computer technology, scientists tracked the development of glaciers in East Antarctica. Spanning approximately 2,000 kilometers of coastline, this area contains as much ice as the entire Greenland Ice Sheet. By comparing historic aerial images with modern satellite data, the researchers determined the glaciers’ movement and changes in size, revealing that the ice has not only remained stable, but has grown slightly over the past 85 years, in part due to increased snowfall.

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

First signs of change

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

“Our results also indicate weakening sea ice conditions, making floating ice tongues of glaciers more vulnerable and unable to grow to the size seen in the first aerial photographs from 1937. We know from other parts of Antarctica that the ocean plays an extremely important role. and is driving the massive and increasing melting we see in West Antarctica, for example,” says Dømgaard.

Hiding from the Nazis

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

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

“By comparing historical aerial images with modern satellite data, we have gained critical knowledge about 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 the glaciers in Antarctica until the 1990s when the first good satellite observations became available.

“The first observations of glaciers are extremely valuable because they give us a unique insight into how the ice evolved in different climates and whether the current changes in the ice exceed the normal cycle of glacier advance and retreat,” explains Dømgaard.

Improving predictive models

According to the researcher, solid, long-term data is key to making accurate predictions of future glacier development and sea level rise, and this study provides new insight into a large area in East Antarctica.

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

The findings were recently published in The nature of communicationwhich is the result of a joint effort by researchers from the University of Copenhagen, the Norwegian Polar Institute, the Norwegian Arctic University and the Institute of Environmental Geosciences in France.

More about the study

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

Reference: “Photos from early aerial expeditions 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 K. Andersen and Anders A. Bjørk, 25 May 2024, The nature of communication.
DOI: 10.1038/s41467-024-48886-x

The research was funded by the Villum Foundation.