Historical aerial photographs of East Antarctica gives a unique insight of the evolution of the ice since the 1930s

Rediscovered historical aerial photographs of East Antarctica offer the earliest insight into ice evolution in Antarctica, revealing that glaciers along nearly 2000 km of coastline have remained stable or have slightly grown over the last 85 years.

The results have just been published in the journal Nature Communications and are the result of a collaboration between researchers from the University of Copenhagen, The Norwegian Polar Institute, The Arctic University of Norway, and the Institute of Environmental Geosciences in Grenoble.

The Antarctic Ice Sheet has received increasing attention from researchers due to its potential to cause significant and rapid sea level rise. Unlike Greenland, we have very limited knowledge about the size and characteristics of Antarctic glaciers before the 1990s, when we began obtaining reliable satellite data. Therefore, early observations of these glaciers are incredibly valuable. They offer unique insights into how the ice has developed through varying climate conditions and helps us determine if current changes are beyond the scale of natural variability. Additionally, long-term glacier data are crucial for developing more accurate models of future changes, as these models rely on existing data to make predictions.

Exploring old photo archives

The majority of the aerial photographs that form the basis of the study were taken during a 1937 expedition arranged and funded by the Norwegian whaling ship owner and consul Lars Christensen. Since then, the photos had been stored at the Norwegian Polar Institute in Tromsø and were largely forgotten. When researchers from the University of Copenhagen learned about the expedition and the possibility of hidden photos in a northern Norway archive, they traveled to Tromsø to examine the collection. The photos were in good condition, and the Villum Foundation supported the idea of funding a thorough investigation.

"This expedition is something entirely different from what we know from modern expeditions to Antarctica. It was virtually uncharted territory for them, as there were very few previous reports from this part of Antarctica. It’s amazing to think that the expedition members were the first humans ever to experience and document many of these areas – so these are truly unique images" says PhD student Mads Dømgaard, the first author of the study.

The expedition photographed approximately 2000 km of coastline, with the aim of producing the first maps of this region of East Antarctica. Unfortunately, these maps were never officially published due to the German invasion of Norway. Despite their age, the photographs are remarkably well-preserved and high-resolution, owing to the use of state-of-the-art equipment at the time. Additionally, the substantial overlap between each photo enabled the researchers to produce 3D reconstructions of the glaciers.

"By comparing these historical 3D models with modern satellite data, we can determine not only if the glaciers have advanced or retreated but also whether they have become thicker or thinner. I think it’s fantastic that these old photos can be used to generate new exciting research results nearly a century after they were taken," says Assistant Professor Anders Bjørk from the University of Copenhagen, who leads the group working with the historical photos.

The Norwegian aerial photos are combined with photos of the same glaciers originating from Australian surveys conducted between 1950-1974. By analyzing these snapshots from different eras, the scientists can track how the glaciers have evolved over time and, in some instances, even calculate how fast they used to flow. Compared to modern data, the ice flow speeds are largely unchanged. While some glaciers have experienced thinning over shorter intermediate periods of 10-20 years, they have generally maintained stability or even exhibited slight growth in the long term, indicating a system that is in balance.

A system in balance – but with a crack in the ice

By comparing their results with historical climate models, researchers found indications that the areas along the coast where glaciers have grown have also seen an increase in snowfall. While this study doesn’t go into the details, scientists believe these changes in snowfall could be influence by several factors like atmospheric warming, ozone depletion and changes in wind patterns. Although the glaciers in the examined regions (which contain enough ice to raise sea levels by 1.15 meters) have been stable since the 1930s, all is not as it should be.

"In this region, we have seen that the ice has remained stable for almost a century. However, our results also show signs of weakened sea ice conditions, making the floating glacier tongues more likely to break and unable to grow as large as we observe in old aerial photos," explains Mads Dømgaard.

"It is important to remember that what we are observing is quite unique, and that other regions of the ice sheet, such as West Antarctica, remain massively impacted by the advection of warm ocean waters, which are increasingly accelerating melt," says Romain Millan, co-author of the study and researcher at the Institute of Environmental Geosciences. He adds, "These changes are also starting to affect glaciers in East Antarctica, which have long been considered stable."

Publication :

Dømgaard, M., Schomacker, A., Isaksson, E. et al. Early aerial expedition photos reveal 85 years of glacier growth and stability in East Antarctica. Nat Commun 15, 4466 (2024). https://doi.org/10.1038/s41467-024-48886-x

Contact CNRS :

Romain Millan : Chargé de Recherche CNRS