ARTICLE - 100 Year Time-Lapse of the Mer de Glace

In the early 20th Century, Swiss aviator and photographer Eduard Spelterini took a series of glass-plate photographs during a trans-alpine gas filled balloon crossing, which today serve as a serendipitous record of glacial retreat. Despite being drawn to the aesthetics of the glacier, Spelterini's main focus in taking these images was the geology of the mountains framing the serpentine Mer de Glace in the Mont Blanc Massif. Spelterini couldn't have predicted how rapidly the landscape he surveyed would change over the next century, but his work has been transformed by aerial photographer and digital visualisation researcher Dr Kieran Baxter into detailed 3D models to create a 100 year 'time-lapse.'

Where photographs overlap, three-dimensional information can be extracted from the two-dimensional images using photogrammetry software, Kieran tells us. Although later surveys have provided more accurate data on the topography of the landscape, Spelterini's antique images offer a striking visual insight into the glacier's past.

Mer de Glace comparison: 1909 and 2017., 196 kb
Mer de Glace comparison: 1909 and 2017.
© Eduard Spelterini / Dr Kieran Baxter

So what's changed? At the area in the foreground of Spelterini's photographs, where the glacier now terminates, the surface has dropped around 100 metres from its position in 1909. Scientists have calculated that the overall volume of the Mer de Glace has diminished by the equivalent of around 700 million cubic metres of water in the last century. According to one study by a team at Joseph Fourier University in Grenoble, if present climatic conditions are maintained, the Mer de Glace will continue to shrink dramatically in the coming decades, retreating by 1200m between now and 2040 - and that's assuming the climate situation doesn't worsen in the meantime.

Dr Kieran Baxter on the Aletsch Glacier in the Swiss Alps., 221 kb
Dr Kieran Baxter on the Aletsch Glacier in the Swiss Alps.
© Dr Kieran Baxter

I sent Kieran some questions to find out more about the process and the project, referencing this article on the project.

How did you get into creative visualisation of landscape heritage?

I'm not an alpine mountaineer but I think that my interest in mountain landscapes came in part from time spent hiking in the Scottish highlands where I grew up. I have also been drawn to glacial landscapes for as long as I can remember. When I began using aerial photography and digital visualisation in my research it became obvious that this would be a good way to tell the important stories that are written into these landscapes.

One of Eduard Spelterini's aerial images of the Mont Blanc Massif, taken in 1909., 175 kb
One of Eduard Spelterini's aerial images of the Mont Blanc Massif, taken in 1909.
© Eduard Spelterini

When and how did you first come across Spelterini's images?

There is a coloured version of Spelterini's 1909 aerial photograph of the Mer de Glace that has been quite widely reproduced. Last year I was discussing how we might use this image with glaciologist colleagues at the University of Dundee and we lamented that, as a monocular image, there was no stereo reference for a 3D reconstruction. Shortly afterwards I stumbled upon an image from the same flight but taken from a different angle and sure enough we found that there were twelve photographs taken in sequence before Spelterini's balloon left Chamonix valley that day. The realisation that these images have survived, and are now freely available in high resolution from the Swiss Helvetic Archives, was the catalyst of the 100 year time-lapse project. As an aerial record of the glacier these photographs are absolutely unique in their antiquity and detail.

The iconic Mer de Glace glacier in 1909., 165 kb
The iconic Mer de Glace glacier in 1909.
© Eduard Spelterini

'Among the archives of Spelterini's alpine aerial photography, images which frame the glaciers as clearly as the Mer de Glace photographs are frustratingly few and far between.' Why do you think this is - why was he drawn to the Mer de Glace in particular?

Spelterini was first encouraged to take a balloon over the Alps by the geologist Albert Heim. There was a scientific purpose behind his recording of the mountain landscape but more of a focus on the geological features and peaks than on the glaciers that occupied the valleys. There was also an aesthetic interest in Spelterini's photography however, and I think that the dramatic double bend of the Mer de Glace probably caught his artistic eye. It is also likely that the Mer de Glace was firmly in the Swiss Aviator's mind before he took off from Chamonix. In 1909 as it is today, France's largest glacier was an important local attraction and the Montenvers cogwheel railway and hotel, which at the time directly overlooked the ice surface, was completed in the same year of the balloon flight. If Spelterini had not visited the site at ground level beforehand then he must at least have been made aware of the Mer de Glace during his preparations for the flight. What we can now see from the position and height of the photographs supports the idea that the Mer de Glace was a key photographic objective directly after take off.

Mont Blanc group with the Argentière glacier., 174 kb
Mont Blanc group with the Argentière glacier.
© Eduard Spelterini

'The images, like Spelterini himself, belong to an altogether more romantic era when our relationship with the environment was defined by curiosity rather than conflict.' Do you think comparison images/time lapses have a greater emotional effect on people with regard to highlighting climate change issues, compared to facts and scientific data? Is this part of the appeal of the process for you?

Images have the potential to reconnect the facts and scientific data to the landscapes that people can experience, which is a big part of the appeal for me. We are intimately connected to our environment, not just in terms of our subsistence, but in cultural and emotional ways too. Looking at Spelterini's photographs it is clear that he loved the Alps and that is one of the reasons why they are such a valuable resource. They are a visual record but they also have a lot to say about the photographer's multisensory experiences beyond the frame. I think we are more likely to be moved by the evidence of climate change when there is a connection to the human stories involved, and the lived experiences of familiar landscapes that we know and love.

Mont Blanc Massif viewed from the north., 166 kb
Mont Blanc Massif viewed from the north.
© Eduard Spelterini

Tell us about your trip to Chamonix to recreate the old photographs. How did you account for snow obscuring the true size of the glacier itself?

In October 2017 we returned to Chamonix to recreate the 1909 photographs based on GPS positions derived from our digital analysis. I was lucky enough to be accompanied by the fantastic adventure photographer and filmmaker Kieran Duncan, who shot the behind-the-scenes footage as well as ground level time-lapse photography around Chamonix valley. All types of aerial photography are completely weather dependent and we spent the first part of the trip waiting around for low cloud and heavy rain to clear. It was a tense time before the flight because we really did not want to go home with no material.

We were watching the high level webcams and one morning we could see the sun breaking through, but it was also clear that all that rainfall in the valley had settled as a blanket of snow at high altitude. While this was aesthetically interesting it was also obscuring some of the geomorphology that we wanted to show and was confusing the glacier margin. Despite the time pressure, we waited another twenty four hours for the snow to thin out and the results were worth it. The original photographs were taken in August and a summer expedition would certainly have produced even more striking comparison photographs, particularly in the lower areas of the glacier that are now debris-covered, but our images did a great job of showing the three dimensional changes.

The retreating glacier terminus in detail., 206 kb
The retreating glacier terminus in detail.
© Dr Kieran Baxter

You recognise the irony in using a helicopter to carry out this work about the effects of global warming. I guess there's no other way around it, as drones can't fly so high?

Spelterini's balloon rapidly ascended to around 2,000 metres above the valley floor before passing the Mer de Glace. This is many times higher than a drone would usually fly so an unmanned aircraft was not a viable solution for the repeat photography. Instead we returned to the original locations in a helicopter, chartered from the nearby Chamonix Mont-Blanc Helicopters and skilfully piloted by Pascal Brun. We first had to convert the positions of the historic photographs into GPS coordinates that we could follow. The helicopter door was open for photography during the entire 30 minute flight. It was an intense but exhilarating experience!

An illustration of Spelterini's balloon flight., 163 kb
An illustration of Spelterini's balloon flight.
© Dr Kieran Baxter / James Gentles

How did you go about the digital 3D processing of the historical photograph and the modelling of both sets of images?

Where there are common features in the photographs, these can be identified and associated with surveyed points in the landscape in order to build a 3D reconstruction in a process called photogrammetry. We can take this one step further using structure-from-motion software and model the historical topography from the original photographs. We do the same process with the modern day photographs except here it is much easier because, unlike with the original set, we are photographing with photogrammetry in mind and collect many extra images so that the software has more data to work with. The 3D comparison that we can then make is even more dramatic than the 2D photographs alone because we can get a sense of the radical change in volume that has happened over the last century.

An early 20th C. postcard of the Montenvers railway station directly overlooking a “sea of ice”., 230 kb
An early 20th C. postcard of the Montenvers railway station directly overlooking a “sea of ice”.
© Public Domain image.

What's your next project?

Over the last year I have been trialling similar methods at the outlet glaciers of the Vatnajökull ice cap in Southeast Iceland. The landscape and the glaciers there are very different but the impact of climate change upon the region is equally staggering. The Alps have historically been thoroughly photographed from the air and there is a lot more work to do in terms of repurposing this archive material to visualise changes in the alpine glaciers. While the picture is different in Iceland, there is some remarkable archive material there as well that we have been exploring. There is also a sense of urgency when it comes to thinking about ways in which these landscapes might not currently be routinely recorded from the air. The glaciers are now changing very fast, so it really is now or never.

Dr Kieran Baxter and Kieran Duncan on board the helicopter used for the project., 219 kb
Dr Kieran Baxter and Kieran Duncan on board the helicopter used for the project.
© Kieran Duncan

Watch the time-lapse and a video about the project below:

Read a comprehensive article explaining the processing of the images.
Read a UKC Article on glacial retreat in the Mer de Glace.
Read a UKC article on the Karakoram Anomaly Project, a study into why glaciers here are stagnating or even growing.

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