Author Climbing in the Queyras, Summer 2013

Wednesday, March 18, 2015

Disappearing Acts:
the Life and Death of a Great Alpine Glacier

Using Nineteenth Century Sources to Study the melting of the Glacier Blanc


..... field geographers can speak with authority about the clarifying effects on the mind of direct physical danger in the real world and there exists a terrible antagonism between field geographers and armchair academics. Not only do those in their armchairs think and write junk, obfuscation, obscurantism, and endlessly convoluted self-referral to their literature in windowless libraries, they do not care about the human condition.”

--William Bunge,
Geography is a Field Subject
Area, 1983

This paper is a shorter version of talk given in 2010 and that will be published later this year.
See the session Measuring Environmental Impact at the Institute of Historical Research, University of London School for Advanced Studies, and my paper Disappearing Worlds.

The Glacier Blanc is the largest glacier in the Southern Alps. From the Dome des Ecrins it reaches a height of 4014 meters down to its snout at 2315 meters, the glacier covers an area of 5.34  square km, extends 5.9 km in length and has a mean slope of approximately 30%.  Measurements have been carried out on the Glacier Blanc since the late nineteenth century with the first real quantitative study in 1887.
Glacier Blanc from the Dome de Neige des Ecrins (click on image to enlarge)

Click on Images to Enlarge
Several important studies have summarized the historical variation of the glacier's mass balance, length and thickness. (see Thibert, E., J. Faure and C. Vincent. 2005. "Bilans de masse du Glacier Blanc entre 1952, 1981 et 2002 obtenus par mode`les nume´riques de terrain". Houille Blanche 2, 72–78.)

Approaching the Glacier Blanc from the Village of Alfoid  (click on image to enlarge)

The approach to the Refuge des Ecrins (click on image to enlarge)
In the center section the main stream the Glacier Blanc is about 800 to 1000 metres wide. The greatest depth of ice occurs near the Refuge des Écrins where it is up to 250 metres deep; some 30 metres less than it was in 1985. My visit  to the glacier this summer showed that the glacier had shrunk back significantly from its previous position leaving only exposed rock near the lower Refuge du Glacier Blanc.

The map below, last updated in in 1991, shows the position of the glacier relative to the refuge, and portrays the snout many tens of meters further down the valley than its present location. The glacier flows at a speed of around 40 meters per year in its central section (in the mid-1980s it moved at 50 m/yr) and at about 30 metres per year near its snout. Its reaction time, i.e. the time that elapses before the foot of the glacier advances or retreats due to major changes in conditions in the accumulation zone, is about 6 years. So the melting we are seeing now is a window into the recent past. 

Map of the area around the Glacier Blanc showing the Refuges Ecrins, Blanc, and Cezanne along with the Glacier Blanc's smaller and rock covered partner, the Glacier Noir  (click on map to enlarge)
Glacier Blanc in the Summer of 2012 (click on image to enlarge)

Schematic of the Structure of the Glacier Blanc (click on image to enlarge)
As with almost all alpine glaciers, the foot of the Glacier Blanc has retreated significantly, as should be evident from the graph of its length below. In earlier times, most recently in 1866, it formed a single glacial system with its southern neighbour, the moraine-covered Glacier Noir, whose streams joined one another above the Pré de Madame Carle. The Glacier Noir is much different in morphology than the Glacier Blanc and is covered with rockfall and boulders from its lateral moraines.
Glacier Noir  (click on image to enlarge)
During the Small Ice Age the combined ice system reached its maximum extent in 1815 and ended roughly at the height of the Cezanne Hut (1,874 m), near the village of Alfoid. Today looking at the Refuge de Cezanne and the Pre Madame Carle it is difficult to believe that the two glaciers ever extended that far down the valley.

Map of Historic Extent of the Noir and Blanc

Refuge de Cezanne near the historic confluence of the Glaciers Blanc and Noir (click on image to enlarge)
There are many sources for glacial heating and the thermodynamics of glaciers is quite complex requiring the solution of several different complex differential equations.

For more of the solutions to theses equations and modeiling of glacier energy balances see the notes Thermodynamics of Glaciers from the McCarthy Summer School at the University of Alaska. Characterizing the heat sources is further complicated by the difficulties in making field measurements for some areas on mountain glaciers that have complex or irregular geometries.

As of 2010 the tongue of the Glacier Blanc lies at a height of about 2,400 m. In the 20th century it is estimated that it retreated by about 1 km, accompanied by a reduction in area of some 2 km². Between 1989 and 1999 alone the glacier lost about 210 metres; it retreated a further 300 metres in the years to 2006. The ice thickness in the centre reduced during the period from 1981 to 2002 by 13.5 metres, an estimated loss in volume of 70 million m³ of ice.

Seracs on the Glacier Blanc in 2012  (click on image to enlarge)
Crucial to the survival of a glacier is its mass balance, the difference between accumulation and ablation (melting and sublimation). Climate change may cause variations in both temperature and snowfall, causing changes in mass balance. Changes in mass balance control a glacier's long term behavior and is the most sensitive climate indicator on a glacier.From 1980-2008 the mean cumulative mass loss of glaciers reporting mass balance to the World Glacier Monitoring Service is -12 m. This includes 19 consecutive years of negative mass balances.

A glacier with a sustained negative balance is out of equilibrium and will retreat, while one with a sustained positive balance is out of equilibrium and will advance. Glacier retreat results in the loss of the low elevation region of the glacier. Since higher elevations are cooler than lower ones, the disappearance of the lowest portion of the glacier reduces overall ablation, thereby increasing mass balance and potentially reestablishing equilibrium. However, if the mass balance of a significant portion of the accumulation zone of the glacier is negative, it is in disequilibrium with the local climate. Such a glacier will melt away with a continuation of this local climate.The key symptom of a glacier in disequilibrium is thinning along the entire length of the glacier.bare, melting and has thinned.

In the case of positive mass balance, the glacier will continue to advance expanding its low elevation area, resulting in more melting. If this still does not create an equilibrium balance the glacier will continue to advance. If a glacier is near a large body of water, especially an ocean, the glacier may advance until iceberg calving losses bring about equilibrium.
Melt Zone outlet in the summer 2012  (click on image to enlarge)
For the first time since 2001 the mass balance of the Glacier Blanc became positive. It has gained 21 cm (water equivalent) over the last few years. However the snout remains very thin and is vulnerable to another hot summer, such as the kind we are experiencing here in the northeastern United States this year.

The last few year’s positive figures have not really effected the glaciers disappearance, as the snout of the glacier is still retreating. 

For more on the Glacier Blanc see glaciologist Mauri Pelto's excellent analysis on his website From a Glacier's Perspective,

Author taking a rest at the Refuge du Glacier Blanc  (click on image to enlarge)
Many historical sources that could help us in our efforts to understand the melting of the great Alpine Glaciers remain locked up in small and obscure local journals and travelers accounts. Many of these where published in the things like the annual of the Alpine Club of France, or in traveler's account like James Forbes' Journals of Excursions in the High Alps of the Dauphine. Forbes, pictured below, was one of the first scientist/explorers of the Alps to understand the principles of glacier mechanics and it is through his Travels through the Alps of Savoy that we can get a sense of how difficult to do glacier science was in the mid-nineteenth century.

There are many more obscure sources however like the measurements of Prince Roland Bonaparte who cataloged the sizes of many of the glaciers of the Dauphine in the 1880s and 90s.

Bonaparte took many photographs (click on images to enlarge) of his Alpine travels and a comparison of the landscape that he encountered with what is currently ice covered is quite shocking. One of Bonaparte's publications, Le glacier de l'Aletsch focuses on his journey across the glacier in 1888-89.

The Aletsch Glacier or Great Aletsch Glacier is the largest glacier in the Alps. It has a length of about 23 km (14 mi) and covers more than 120 square kilometres (46 sq mi) in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed by three smaller glaciers converging at Concordia, where its thickness is estimated to be near 1 km. It then continues towards the Rhone valley before giving birth to the Massa River.

The Aletsch, because of its size is one of fastest shrinking glaciers in the alpine chain as it apparent from the three images below taken in 1979, 1991 and 2002. (click on images to enlarge)

The Aletsch Glacier has been studied for almost 200 years. This data has been compiled by the Swiss Glacier monitoring network and is shown graphically below.

The entire area around the glacier has been declared a UNESCO world heritage site. The United States Geological Survey has begun a Repeated Photographs Study that seeks to show in dramatic form the extent of glacial melting using historic photos. For example in Glacier National Park they have looked closely at the Grinnell Glacier from various vantage points.

Most alpine glaciers are in trouble and some have become dangerous as their melting has caused the formation of large glacial lakes in places where few had been before. About a decade ago a second lake appeared in front of the Arsine glacier just across the Barre des Ecrins from the Glacier Blanc. I visited this series of glaciers several year ago just after the snow melt, crossing the large moraines that are left behind from its larger bygone days.

The author approaching the calving front of the Arsine Glacier (click on image to enlarge)

Arsine Glacier as mapped in 1979 and in 2008 (click on images to enlarge) Note the creation of a second lake due to the melting glacier

To give the viewer an idea of the scale of these glaciers, note the author in the center of the photograph

Glacial melting not only affects the activities of climbers and geographers but also the daily lives of those who live in villages near mountain environments and those make their livings from them. One of the best recent studies glacial melting from this perspective can be found in the book In the Shadow of Melting Glaciers: Climate Change and Andean Society by Mark Carey. Carey's book has been the subject of much discussion and was the subject of an H-Environment Round table Review in 2011.

For more on the melting of glaciers worldwide and their mapping go to the resources available at Glacier Works and at the Extreme Ice Survey .

For more on glaciology and the effect of climate change on glaciers see:

H. Holzhauser, "Glacier Fluctuations in the western Swiss and French Alps in the 16th Century," Climate Change 43 (1999) : 223-37.

H. Holzhauser, "Glacier and glacial-lake variations in west-central Europe over the last 3500 years," The Holocene 15 (2005): 791-803.

Roger Hooke, Principles of Glacier Mechanics (Prentice Hall, 1998)

A. Nesje and S.O. Dahl, Glaciers and Environmental Change (London: Arnold, 2000)

Ben Orlove, Ellen Wiegandt and Brian Luckmann, Darkening Peaks: Glacier Retreat, Science and Society, (University of California Press, 2008)

W.S.B. Patterson, The Physics of Glaciers (Butterworth-Heinemann, 2001)

Daniel Steiner, "Two Alpine Glaciers over the Past Two Centuries: a scientific view based on pictorial sources," in Darkening Peaks (2008): 83-99

Sunday, December 07, 2014

New Three-Dimensional Models of the Melting of the 
Mer De Glace, Chamonix, France

Le Centre de Researches sur les Ecosystemes d' Altitude has published a times series of three-dimensional views of the Mer de Glace....and a new glacier coverage map...dramatic....






Thursday, October 30, 2014

His aqueducts and his cartography:
Frontinus, Roman law and the missing maps of the waters of Rome

The foundations of the science of land measurement lies in practical experience, since the truth about sites or area cannot be expressed without lines that can be geometrically measured.

                                                                                                   --Frontinus, De arte mensoria

According to R.H.Rodgers, 'obscurity veils the early career of Julius Frontinus,' who in the year 97 was appointed curator aquarum of the city of Rome. Frontinus wrote two groups of texts that are important to us here in our study of Roman cartography; those being De Aquaeductu urbis Romae and a series of texts on Roman surveying. The work that remains extant on Roman surveying is found in the Corpus Agrimensorum and is very fragmentary. Karl Lachmann (shown below), who worked on the first edited edition of the text, believed that the full work comprised two books, the first consisting of De Agrorum Qualitate and De Controversiis, the second work containing De Limitibus, De arte Mensoria and some other more fragmentary texts from Urbicus, another writer on Roman surveying who may have copied his work from the now missing parts of Frontinus.

Besides his interest land surveying however, Frontinus is more well-known for his text on the aqueducts of Rome. (For more on this see the website run by Katherine Rinne) In the text of De Aquaeductu urbis Romae he discusses the fact that he made maps used in the administration of the aqueducts. In the prologue to the book Frontinus refers to his work as a commentarius, and explains that it is a collection of data and other materials that he made primary for 'himself'. The contents of the book are quite technical and numerical, pertaining to sizes of individual aqueducts, the dates they were built, pipes and their sizes, the quantities of water delivered and legal matters relating to the right of private individuals to the use of public water. Although most of the material serves an adminstrative aim some of the text deals with methodological issues and it is these that are of interest for historians of cartography. In Chapter 17 of his book on aqueducts Frontinus writes:

Non alienum mihi visum est longitudines quoque rivorum cuiusque ductus etiam per species operum complecti. nam cum maxima huius officii pars in tutela eorum sit, scire praeposiutum oportet quae maiora impendia exigant. nostrae quidem sollicitudini non sufficit singula oculis subiecisse; formas quoque ductuum facere curavimus ex quibus adpareret ubi valles quantaeque, ubi flumina traicerentur, ubi montium lateribus specus adpliciti maiorem adsiduamque petendi ac muniendi vi exigerent curam[1].

Which translates as:

It has seemed to me not unfitting to include as well as description of the lengths and courses of each aqueduct, according to the classifications of construction. Because the greatest part of the duties of this position lies in the maintenance of the lines, the man in charge must know what thongs demand greater outlays. My sense of responsibility has not been satified with personal examination of particular items. I have also taken care to prepare maps of the lines, from which it is clear where there are valleys and how great they are, where rivers are crossed, and where channels attached to the sides of mountains demand greater and constant attention...for their repair.

Hence we learn here that Frontinus had detailed maps made of the aqueducts describing not only the lines themselves but also the topography of the surrounding countryside that they traversed. According to Harry B. Evans, in his Water Distributon in Ancient Rome, (Michigan, 1994), "Frontinus' mapmaking merits closer attention." Evans postulates that Frontinus' data, which he gives in the text on aqueducts, is in fact derived from the maps that he had made and that those sections of the text describing the actual lines are commentaries on the maps themselves. There are other indications in the text that Frontinus is using maps as he pinpoints some of the sources of the aqueducts by using exact spatial references to the existing road system outside of Rome.

  Although none of Frontinus maps survive there are maps on inscriptions that show what aqueducts maps may have looked like. An example shown here (CIL 6.1261) displays in graphic form the lines of an aqueduct and the epigraphy gives indications of water flow and on what legal terms individuals may draw water from particular lines. The inscription contains the names of the people who shared the channel that came off the aqueduct, the volume of water that they where alloted, and the scheduled times that they could take that allotment.

The inscriptions translates as:

a. for Thyrsis, freedman of Augustus, two pipes from the second to
the...hour, on the fourth day before.. 
b. for the freedman of C. Julius
Caeser, C. Bicoleus Rufus Squaterianus, one pipe... 
c. to the Aufidianum of Julius Hymetus, two pipes from the second
to the sixth hour... 
d. To Vibius...pipes, to C. Bicoleus, Freedman of C. Julius
Caesar,... pipes from the sixth hour until sunset...

There are several known examples of this type of inscription and another is shown below (CIL 14.3676). This inscription describes a shared channel related to the supply of water at Tibur, a rural area outside Rome. The stone containing the inscription is found built into the side of the Church of Saint Peter at Tivoli and it preserves a fragment of a map showing two channels. The inscription itself lists the people to whom the water is to go to, the amount of water they have been alloted, and the time of day when it may be taken. (for more on water rights see Cynthia Jordan Bannon, Gardens and Neighbors: Private Water Rights in Roman Italy, Michigan, 2009). As Evans says, all of this deserves further work....and can help us understand some of the lesser known aspects of Roman cartography and its application.

Of all those who have studied the topography of Rome and its ancient aqueducts perhaps the most important was Thomas Ashby who surveyed their extant remains in in Rome and its outskirts for many years at the beginning of the 20th century. Ashby's work, published after his death by his wife will never be improved upon since many of the ruins he examined have long since disappeared.

Many of Ashby's notebook still survive and his photographs and drawings are an unparalleled resource any scholar interested in these great Roman constructions.

[1] I have used the new edition of Frontinus by R.H. Rodgers, "De Aquaeductu urbis romae", Cambridge Classical Texts and Commentaries 42, 2004.