Research Shows How Climate Change Drives Glacier Retreat

Shrinking glaciers are oft-cited examples of the effects of anthropogenic climate change, providing dramatic imagery in different parts of the world. However, this has mostly been based on global aggregates of glacier extent. Differing opinions also exist about the best way to measure glacial change all over the world.  A recent study by Roe et al., published in Nature Geoscience, confirms that climate change has contributed to the shortening of numerous glaciers around the world, but the study is not immune to controversy surroundings the methods used.

Retreating glaciers, such as these in the Himalayas, are a popular symbol of climate change (Source: NASA/Creative Commons).
Retreating glaciers, such as these in the Himalayas, are a popular symbol of climate change (Source: NASA/Creative Commons).

Using a combination of meteorological data and observations of glacier length, Roe et al. studied the influence of climate on 37 glaciers between 1880 and 2010. The glaciers were selected based on the continuity of length observations and the need for a wide geographical distribution.

Glacier mass-balance records are a more direct measure of the effect of climate than glacier length as they measure the difference between the accumulation and ablation (sublimation or melting) of glacier ice. However, most mass-balance records do not extend for more than two decades, contributing to the previous lack of confirmation of the effect of climate change on individual glaciers around the world.

The use of observations of glacier length helped to overcome this obstacle, but challenges were still encountered in obtaining long, continuous data sets, particularly for regions such as Asia and South America. In conversation with GlacierHub, Roe shared that many factors can affect the availability of continuous data sets. “For example, the collapse of the Soviet Union led to many glacier observation programs being abandoned,” he stated.

The researchers tracked changes in the length of 37 glaciers, including those highlighted here (Source: Roe et al./Nature Geoscience).
The researchers tracked changes in the length of 37 glaciers, including those highlighted here (Source: Roe et al./Nature Geoscience).

An additional challenge arose from the variation in conditions experienced by each glacier. “Every glacier is a unique product of its local climate and landscape,” Roe shared, citing the example of maritime glaciers, which typically experience a large degree of wintertime accumulation variability. “This can mask the signal of a warming that, so far, has mainly impacted the summertime mass balance,” he added.

Nevertheless, Roe et al. found that there was at least a 99% chance that a change in climate was needed to account for the retreat of 21 of the glaciers studied. “Even for the least statistically significant (Rabots Glacier in Sweden), there was still an 89% chance that its retreat required a climate change,” Roe said.

As glaciers tend to have decadal responses to changes in climate, their retreat since 1880 is likely to be a result of twentieth-century temperature trends. They also act as amplifiers of local climate trends, providing strong signal-to-noise ratios that serve as strong evidence for the effects of anthropogenic climate change. For example, one of the glaciers included in the study, Hintereisferner in the Austrian Alps, retreated 2,800m since 1880, with a standard deviation (a measure of the deviation of values from the mean) of 130m. This value is small compared to the amount of retreat, providing a strong signal of change.

Hintereisferner was one of the 37 glaciers included in the study (Source: Creative Commons)
Hintereisferner was one of the 37 glaciers included in the study (Source: Woodsiailvensis/Creative Commons).

“We hope that these results will lead to a stronger scientific consensus about the cause of glacier retreat. The last round of the Intergovernmental Panel on Climate Change was quite timid, concluding only that it was ‘likely’ that a ‘substantial’ part of glacier retreat was due to human-caused climate change,” Roe added. IPCC nomenclature would make it “very likely” (≥90%) that all but one of the glaciers in this study have retreated because of climate change, allowing for stronger conclusions to be drawn.

Excitement about the results of this study was shared by Joerg Schaefer, professor at the Lamont-Doherty Earth Observatory: “Under Roe’s lead, the really smart glacier people find ways to explain this strange observation that glaciers are highly individual beasts if you look at short time scales (years and decades), but behave like a flock of well-behaved sheep when you look at longer (centennial and millennial time-scales),” Schaefer said in an interview with GlacierHub. “This will help us a lot down the road to better predict rates of glacier change for the next century.”

In contrast, Mauri Pelto, professor of environmental science at Nichols College who has been involved in the North Cascade Glacier Climate Project for 34 of years, expressed that the paper was interesting but not the first confirmation of glaciers being impacted by anthropogenic climate change. “This does not mean it is not worth writing about,” said Pelto, “but it needs to be placed in the context of the other key studies that were both earlier, and, I believe, stronger.”

For example, the authors looked at fewer glaciers than Oerlemans et al. (2005) while modelling each in more detail. Pelto notes that they also used far less data than Zemp et al. (2015) in making an even more compelling statement on the status of glaciers. Finally, the authors are not the first to conduct an attribution study: note Marzeion et al. (2014). While their statistical method is quite robust, their modelling approach that generates data does not have an impressive verification record, according to Pelto.

“Other recent studies better represent the certainty of glacier change being driven by climate,” Pelto concluded.

These opinions indicate that glacier retreat continues to attract attention and stimulate active debate, pointing to the importance of glaciers and climate change. The approach used in this study relies on glacier length, a less precise measure than mass-balance. However, its value lies in the ability to consider long meteorological and glacier length records for a number of glaciers, contributing to an important and growing body of knowledge about the effects of anthropogenic climate change on glaciers all over the world.

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Rediscovering Julius von Haast, Pioneer of Glaciology

In the history of glaciology, New Zealand’s German-born Julius von Haast ranks as an influential but otherwise little-known pioneer. In the 19th century, Haast’s scientific explorations led him to glacier-rich areas across New Zealand where he gave names to landforms, including the well-known Franz Josef, Hooker, and Mueller Glaciers on the West Coast’s South Island. A recent report by Sascha Nolden for the Canterbury Museum strives to recognize the overlooked life and legacy of Haast, who to this day continues to influence glacier researchers around the world.

Julius von Haast (Source: The Encyclopedia of New Zealand)
Julius von Haast (Source: The Encyclopedia of New Zealand).

“Famous? No, Julius is not famous, even today,” said Joerg Schaefer, a professor at Columbia University’s Lamont-Doherty Earth Observatory, to GlacierHub. “But he was indeed a great explorer and glacier geologist in New Zealand. He was not only a fellow citizen of mine, but one of my heroes.”

Haast has served as a role model for modern-day scientists like Schaefer, with his work paving the way for future scientific research. “Our team has worked in New Zealand for 15 years following in Haast’s footsteps,” said Schaefer.

By scrutinizing archival material such as manuscripts, letters, photographs and sketches held in the collections of the Alexander Turnbull Library, Nolden carefully rediscovered Haast’s biography, documenting Haast’s notable research, exploration, institution-building and collegial cooperation that continues to influence today’s scientists.

“Haast was one of the leading New Zealand scientists of the second half of the nineteenth century,” writes Nolden, research librarian at the Alexander Turnbull Library, in his report. “He was a remarkable individual noted for his stamina and perseverance in the face of obstacles, ranging from the mountain wilderness to the tangles of provincial bureaucracy.”

Born in 1822 in Bonn, Germany, Haast first studied geology and mineralogy at the University of the Rhine, although he never graduated. He later spent time in the high mountains of New Zealand in the 1860s, visiting the region’s glaciers and making original watercolor sketches of the mountains. His sketches and maps have been useful to glaciologists as they attempt to date various landforms.

It was during Haast’s explorations in New Zealand that he began to give names to glaciers, creating what he called a “Pantheon” of landforms named for prominent individuals from leading scholars to emperors, according to chief paleontologist Charles Alexander Fleming. In addition, his studies of the effects of past glaciation became the basis for later works on glacier geology.

Painting of the Southern Alps from the Godley river bed, by John Gully, from a sketch by Johann Franz Julius von Haast (Source: the Alexander Turnbull Library)
Painting of the Southern Alps by John Gully, from a sketch by Julius von Haast (Source: The Alexander Turnbull Library).

In 1862, Haast specifically surveyed the geology of the Canterbury district and visited its glaciers. His mapping and mountaineering expeditions of Mueller Glacier, for example, became a valuable first-hand resource to Thomas Lowell et al.’s research on the Rhizocarpon calibration curve (an application tool to assess Little Ice Age glacier behavior) for the Aoraki/Mount Cook area.

In his report, Nolden references 165 of Haast’s drawings from South Island surveys from 1860 to 1868 that can be found in the Haast archives. Other panoramic watercolors of the Southern Alps and map sketches of the glacier geology of New Zealand are in private collections such as in the Hochstetter Collection Basel. In addition to these works, Haast published one book of his research, entitled “Geology of the Provinces of Canterbury and Westland, New Zealand: A Report Comprising the Results of Official Explorations” (Haast 1879). Other useful, unpublished manuscripts written by Haast have also been located and preserved.

Interestingly, despite these archives, little is known about Haast’s early life. Almost everything written about him concerns what he did after arriving to New Zealand, a fact that is often frustrating to historians. The most complete source of Haast to date is a biography written by his son, Heinrich von Haast.

“For the biographer, Haast is a difficult subject,” writes Nolden in his report. “Relatively little is known about him for the period prior to his arrival in Auckland on 21 December 1858, and this is in no small part due to the subject’s own contribution to myths and misinformation.” Knowing about Haast’s upbringing, education, work, family and friends before he came to New Zealand might be helpful in explaining what drove him to accomplish so much during his lifetime.

Julius Haast, ‘From Spur about 6500 above sea level, leading to Mt Cook, over the Great Tasman Glacier & the Murchison Glacier.’ (Source: Dr Albert Schedl Collection, Vienna).
A sketch by Julius Haast of the Mt Cook area, over the Great Tasman Glacier & the Murchison Glacier (Source: Dr Albert Schedl Collection, Vienna).

Colin Burrows, a New Zealand plant ecology educator and professor at University of Canterbury, was one scientist who studied Haast’s explorations in New Zealand, especially the Southern Alps. His book, “Julius Haast in the Southern Alps,” published in 2005, retraces Haast’s exploratory journeys in the mountains and examines his theories of glaciation. But according to Nolden, much of what has been written and repeated about the life of Haast prior to his arrival in New Zealand has been largely based on conjecture.

“Haast’s efforts to forge a new identity for himself and escape his past have become more fully apparent with the present research,” writes Nolden in his report. “Haast was prepared to change both his identity and allegiances whenever it seemed to serve his purposes – to leave behind his past and build a better future for himself.”

What is clear about Haast is that he spent his life exploring, studying and innovating. Although he is not widely known today, his contributions to glaciology became the basis of modern glacier studies. Haast’s efforts reveal how the work of one scientist can pave the way for subsequent generations of scientists. Thanks to the recent efforts of the Canterbury Museum and historian Sascha Nolden, we now have a better understanding of the historic contributions of one of glacier geology’s early pioneers.

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Photo Friday: Glacial Moraine Maps as Art

Joerg Schaefer, a geoscience researcher at the Lamont-Doherty Earth Observatory at Columbia University, specializes in tracing the history of moraines through cosmogenic radionuclide dating. He depicts the results of his research in maps of moraines–the accumulation of glacial till and sediment at the end, or snout, of a glacier, or along its sides. While scientific in nature, the maps themselves are visually stunning- prompting GlacierHub to showcase some of the glacial maps from Schaefer’s research.

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Joerg Schaefer
Joerg Schaefer, photo from personal website

Schaefer is most interested in studying the dynamics of earth surface processes and their interaction with climate, as well as ice ages and the dating and quantifying of changes in earth’s climate and landscape. He can be contacted here.

 

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