Climate research in the geologic past

Fig.1. Global map as published by Lyell in his "Principles of Geology" (8th edition 1850) to illustrate the past climatic changes.

The climate of a region, as experienced by daily observations of a cool morning and hot midday, was for very long time considered simply the result of the height of the sun above the horizon. This idea forced a very simple view of the distribution of climates on Earth, to the poles temperature dropped, to the equator it raised, forming so large parallel climatic belts. Such a static view of the Earth also didn’t need or even allow climate changes in the past or in the future time.
With the establishment of the deep geological time by the first geologists and naturalists it became clear that not only the distribution of sea and land changed over time, but so did climate.

Read on how Lyell explained climate change by shifting "pseudo"-continents over the globe in the post at the American Scientific Guest Blog.

Glacier outburst floods threat

Glaciers can influence societies in their catchment area in different ways, they act as a water storage for dry summers, but glaciers can also trigger geological catastrophes and endanger people.

Glacier outburst floods (GOF) refer to the rapid and sudden discharge of water from within a glacier or from an ice-dammed lake, within minutes to hours a flood wave occurs possibly damaging infrastructures and killing people kilometres away from the glacier which initiated the disaster. In the Alps and North America most outburst floods occur in summertime when during melt-season large quantities of water can accumulate inside the glacier or as ice-dammed lake.

In the Andes and the Himalaya also a second type of floods is common, outbursts from moraine-dammed lakes, referred as glacial lake outburst flood (GLOF).
The area between the moraine and the retreating glacier can be filled with the melt-water, and as the glacier continues to shrink the lake continues to grow. Various processes can lead to the failure of a moraine dam, waves and currents of the lake can erode the dam, ice contained in the dam can melt, the detritus forming the dam can settle with time and so lowering the effective height of the dam.

Fig.1. Laguna Paron (4.140m a.s.l. Cordillera Blanca - Peru, foto from Wikipedia) in 2009, a lake dammed by the debris-mantled glacier Hatunraju with a capacity of 75 million cubic metres before the lake level was lowered by 20 meters artificially by tunnelling through bedrock on the left of the moraine dam. The lake is surrounded by moraines 250m high. It is unknown how stable the moraine of Hatunraju is, if this dam fails a flood of around 50 million cubic metres could sweep downstream and severely damage the town of Caraz, 16 kilometres away.
The worst glacial lake outburst in historic time was caused by the failure of such a moraine-dam in Peru. December 3. 1941 the town of Huaraz was partially destroyed by a flood that killed 60.000 people.

Floods resulting from moraine-dam failure have been increasing in frequency in the Himalaya over the past 70 years or so, although in terms of loss of life they have been by accident much less disastrous then in the Andes.
One of the best-documented outburst floods in Nepal took place on 4. August 1985 when the terminus of the Langmoche Glacier in the Khumbu Himal collapsed into Dig Tsho glacial lake (Video), creating a displacement wave hat overtopped the moraine dam and triggered its collapse. Estimated 10 million cubic metres of water were released - the wave destroyed a power plant and five people were killed and eroded and destabilized the valley floor for 90 kilometres downstream.

This case triggered major research projects of potential dangerous glaciers and glacial lakes, until 2004 more then 20 potentially dangerous lakes in Nepal and 24 in Bhutan were identified, one of the most impressive and dangerous case was lake Tsho Rolpa (4.450m a.s.l.), fed by the Trakarding Glacier. By 2002 the lake was 3,5 kilometres long, 0,5 kilometres width and 135m deep, with an estimated volume of 110 million cubic metres. The moraine damming the lake up was 150m high, with a core of decaying ice.
Emergency measures were initiated with the installation of an early-warning system to detect downstream travelling a flood-wave and later by the construction of an artificial spillway, lowering the lake by 4 metres.
However these are considered only temporary solutions, as a lowering of the lake level by at lest 15 to 20 metres is necessary to prevent spillover or failure of the dam crest, a costly procedure in this region.

This last case shows also the financial problems facing poor countries, often disaster prevention or mitigation are limited by the available resources, and considering the continuing glacier retreat expected in the next decades the increase of problematic lakes (both in number and volume) will by of major concern in the future.

Fig.2. The glacierized Himalayan border region of Bhutan (bottom) and Tibet (top) seen in a satellite image. From the crest of the mountain range clean glaciers flow northwards onto the Tibetan Plateau, while debris-mantled glaciers flow south into densely forested valleys.
At bottom right are a series of moraine-dammed lakes and incipient lakes, formed by the rapid coalescence of supraglacial ponds. The large lake at the very right is lake Luggye Tsho. A breach of the dam in 1994 led to severe flooding and loss of life up to 200 kilometres downstream. (ASTER-image by NASA, 08 June 2006).

Bibliography:

HAMBREY, M. & ALEAN, J.(2004): Glaciers. 2nd ed. Cambridge University Press: 377
HORSTMANN, B. (2004): Glacial Lake Outburst Floods in Nepal and Switzerland. New Threats Due to Climatic Change. Germanwatch - Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung.
KALTENBORN, B. P., NELLEMANN, C., VISTNESS, I. I. (Eds) (2010): High mountain glaciers and climate change - Challenges to human livelihoods and adaptation. United Nations Environment Programme, GRID-Arendal.

Modeling Glacier Change 2000-2100

According to a simulation by researchers of the University of Alaska (RADIC, V. & HOCK, R.) and based on various scenarios of precipitation change and a temperature increase, with a mean value of ca. 2°C, as predicted by most climate models, until the year 2100 the 120.000 glaciers located (mainly) in middle latitudes will experience a massive loss of 21% of the actual ice volume.

Observing the reactions of more than 300 glaciers to the climatic change in the period of 1963 to 2004 the models were extrapolated to simulate a significant increase in temperature and slight increase in precipitation and the effects of these variables on the mass balance of the glaciers.
The projections show in the 19 chosen glacierized regions different glacier retreat values, depending from factors like elevation, surface properties and effective temperature rise in the region.
According to the proposed scenarios, mountain ranges in temperate climatic zones will experience the most massive volume change, in the European Alps glacier will loss up to 75% of the actual ice volume, similar values to the New Zealand Alps with 72% and the Caucasus.
In contrast mountain ranges with a high average altitude, like in Asia or the Andes, will experience much lower loss percentages, with an average value of 20%.

I discussed a previous research dealing with possible effects of such glacier retreat on human society in this post.

Fig.1. Regional twenty-first-century glacier volume change expressed in per cent from initial volume in year 2000, the results are presented for 19 regions based on temperature and precipitation projections from the ten applied climatic models, after RADIC & HOCK 2011.

Fig.2. Example of glacier retreat in the Alps in the past 100 years: The Waxegg-glacier in the Zillertaler Alps at the border between Austria and Italy ca. 1900-1903 and 2006. Historic image from ROTHPLETZ, A. & PLATZ, E. (1903): Alpine Majestäten und ihre Gefolge - Die Gebirgswelt der Erde in Bildern, 268 Ansichten aus der Gebirgswelt.
For the history of glacier monitor projects see this post.

Bibliography:

RADIC, V. & HOCK, R. (2011): Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise. Nature Geoscience doi:10.1038/ngeo1052

The discovery of the ruins of ice

"It has already been said, that no small part of the present work refers to the nature and phenomena of glaciers. It may be well, therefore, before proceeding to details, to explain a little the state of our present knowledge respecting these great ice-masses, which are objects of a kind to interest even those who know them only from description, whilst those who have actually witnessed their wonderfully striking and grand characteristics can hardly need an inducement to enter into some inquiry respecting their nature and origin."

James, D. Forbes (1900): "Travels Trough the Alps." [page 17]

Fig.1. C. Wolf and M. Descourtis "La Grosse Pierre Sur Le Glacier de Vorderaar Canton de Berne Province d'Oberhasli", Amsterdam 1785.

Today worldwide glaciers were studied and monitored as climate proxies, and the recent measurements show that almost all of them are retreating fast. The story about glaciers, their influence on the landscape and their possible use to reconstruct and monitor climate is an intriguing one, with many triumphs, setbacks and changes of mind.

For centuries, if not even millennia, the high altitude belt of mountain ranges were a region visited and travelled by man, however also haunted and forbidding places. The glaciers, masses of ice enclosing peaks and extending their tongues into valleys, were considered the residence of mountain spirits, then during the medieval times the prison of damned souls (the Italian poet Dante Alighieri 1265-1321 imagined the centre of hell as a frozen wasteland) and the playground of demons, who from time to time send avalanches and debris flows into the valley.
Despite these myths there was some early insights of what glaciers actually really are made, the Greek historian and geographer Strabo (63 - 23) describes a voyages trough the Alps during the reign of Augustus and mentions

"…there is no protection against the large quantities of snow falling, and that form the most superficial layers of a glacier…[]. It's a common knowledge that a glacier is composed by many different layers lying horizontally, as the snow when falling and accumulating becomes hard and crystallises...[]."

However the knowledge got lost, and was only rediscovered during the Renaissance. Leonardo da Vinci´s (1452-1519) is considered one of the greatest Renaissance-geniuses, he studied anatomy, biology and geology, however regarding the glaciers of the Alps his ideas were somehow confused, the thought glaciers were formed by not melted hail accumulating through the summer. But soon the study of nature experiences an incredible raise, and glaciers find place in various descriptions of travelling scholars.

Between 1538 and 1548 glaciers were labelled (even if not depicted) with the term "Gletscher" on topographic maps of Switzerland. In his account on the Swiss land the Theologian Josias Simler in 1574 describes the Rhone-glacier.
The first historic depiction of a glacier is considered the watercolour-paint of the Vernagtferner in the Ötztaler Alps from 1601. The Vernagtferner was a glacier that repeatedly dammed up the Rofen-lake (named after the Rofen-valley), which outbursts caused heavy damage and loss of property, particularly in the years 1600, 1678, 1680, 1773, 1845, 1847 and 1848.
In 1642 the Swiss editor Matthaeus Merian the Older in his "Topographie Helvetiae, Rhaetiae et Valesiae" published various copper engravings of glaciers, and in 1706 Johann Heinrich Hottinger is interested to explain the motion of "the mountains of ice" in his "Descriptio Montium Glacialium Helveticorum."
Johann Jakob Scheuchzer, visiting in the year 1705 the Rhône Glacier, published his observations of the "true nature of the springs of the river Rhône" in the opus "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", and confirms the idea that glaciers are formed by the accumulation of snow and they move and flow.

Fig.2. The description of the Rhone glacier according to Scheuchzer´s "Itinera per Helvetiae alpinas regiones facta annis 1702-1711", the engraving shows the "false springs at the mountain Furca" (M, N, O - left and right of the picture) and the "true springs" (J, K, L) coming from the snout of the "great glacier" (A-F), surrounded by the "small glacier" (G, H).

The increasing interest to study glaciers in the Alps is also encouraged by enthusiastic travel reports; in his "Voyage pittoresque aux glaciers" the A.C. Bordier of 1773 describes the Bosson glacier as a "huge marble ruins of a devastated city".
The naturalist Horace Benedict de Saussure (1740-1799) is fascinated by the mountains of his homeland, he climbed mountains around Geneva since 1758, and after 1760 he travelled more than 14 times trough the Alps (considering the possibilities in this time an extraordinary achievement). Between 1767 to 1779 the first volume of his "Voyages dans les Alpes" is published, were he reassumes his observations and theories about the visited glaciers, he recognized moraines and large boulders as the debris accumulated by the glacier tongue and proposes to map them to interfere the former extent of glaciers. Despite this exact statement, de Saussure failed to connect large boulders found in the foreland of the mountains to the glaciers of the Alps. He assumed that these rocks were transported on their recent locations by an immense flood. That seemed to explain why most of the boulders found scattered around the plains of Germany came in first place from the regions of Scandinavia, where the same lithology where found in the crystalline continental basement, like Precambrian metamorphic rocks and paleozoic sediments. The theory worked lesser to explain the foreland Alpine rocks - to transport boulders from the Alps the flood at least had to reach 1000 of meters.
The idea of a flood as the explanation for "glacial" deposits became largely accepted, it seemed to fit the description of the biblical flood; even Lyell and Darwin assumed that huge erratic boulders were transported by swimming ice drafts on top of a flood wave.
That glaciers could propagate far out of their valleys was however not an unusual idea for local inhabitants, who observed and experienced the growth and recess of glaciers. In academic circle this approach was a little more difficult.
A contest thought to demonstrate the former extension of Swiss glaciers initiated by the Swiss pastor Jakob Samuel Wyttenbach in 1781 (maybe inspired be the advance of the Alpine glacier in 1770) didn't arise any interest.

"Could it be proven to ourselves on the available documentation that both by the progress of our ice mountains as by our misbehaviour once for pasture most suitable land is currently covered by ice…[]"

There were only careful speculations considering a former expansion of glacier: the geologists James Hutton (1726-1797) and his friend John Playfair (1748-1819) speculated about glaciations of the northern hemisphere. In 1826 a publication by the Danish mineralogist and mountain climber Jens Esmark (1763-1839) was translated into English, in this paper Jesmark discussed the possibilities that glaciers where much greater in the past then today. J.D. Forbes and Robert Jameson (who were the geology professors of Charles Darwin at Edinburgh University, Darwin in his autobiography of 1876 remembers "The sole effect they produced on me was the determination never as long as I lived to read a book on Geology or in any way to study the science.") discussed glacial theories during their lectures. And even Buckland, who still in 1831 argued "northern region of the earth seems to have undergone successive changes from heat to cold", in 1837 was converted to Lyell's uniformatism and considered that sudden changes, like an ice age and glacier expansion, simply don't happen in geology.

In 1815 Jean Pierre Perraudin, a chamois hunter in the Val de Bagnes, told to the engineer Ignatz Venetz his theory that the glaciers once covered the entire valley, and Venetz mapped features that made him even recognize that once the entire Swiss was covered by ice. Vernetz´s lecture on the assembly of the Swiss association for natural history in 1829 found little interest, only Jean de Charpentier, director of the salt mine in the city of Bex (Western Swiss), who 14 years earlier had meet and discussed with Perraudin, this time accepted and got interested in this theory.
He begun a detailed mapping project, and in 1834 Charpentier presented again before the Swiss association the results of his investigations, but the flood theory had still much supporter. One of the critics in the public was a former student of Charpentier, named Jean Louis Rodolphe Agassiz, respected palaeontologist by the establishment. Charpentier invited Agassiz to visit the city of Bex and surrounding mountains, and to observe glaciers.
In the following year (1837) Agassiz held an enthusiastic lecture about glaciers, ice ages and ice shields, and in 1840 published a detailed study of modern glaciers, their deposits and their spurs in his "Etudes sur les glaciers."
Agassiz experienced the same scepticism as many other ice-age proponents before.

"I think that you should concentrate your moral and also your pecuniary strength upon this beautiful work on fossil fishes .... In accepting considerable sums from England, you have, so to speak, contracted obligations to be met only by completing a work which will be at once a monument to your own glory and a landmark in the history of science ...[ ]...No more ice, not much of echinoderms, plenty of fish..."
Alexander von Humboldt in a letter to Agassiz on 2. December 1837

However Agassiz had good connections to the most important geologist of his time. Soon he could persuade William Buckland and later Charles Lyell. After that the most respected geologist gets convinced, the rest, as always, is history:

"advice - never try & persuade ye world of a new theory - persuade 2 or 3 of ye tip top men - & ye rest will go with ye stream, as Dr B. did with Sir H. Davy and Dr. Wollaston in case of Kirkdale Cave"
Edward Jackson, about an advice given by his professor Buckland in 1832

Fig.3. Reconstruction of the glacier that filled the valley of St. Amarin (southern Vosges, France), probably the first tentative reconstruction of an ice age glacier - from COLLOMB (1847): "Preuves de l´existence d´anciens glaciers dans les vallées des Vosges."

Agassiz research on the Unteraar-glacier established the foundations of glaciology; he recorded the dimension of the glacier, his velocity and even ventured inside the glacier by passing trough a glacial mill. Soon after 1850 the measurements methods introduced by Agassiz were carried out on various glaciers of the Alps and repeated nearly every year.

Fig.4. The Hintereis-glacier (in the centre of the picture), Hochjoch-glacier (left) and the Kesselwand- glacier, drawing by Schmetzer 1891, the Hintereis-glacier is one of the glacier with the longest active monitoring program, values about his length change reach back to 1848, since then the glacier lost 3km of his tongue.
"Aus den tiroler Alpen: Der Abschluß des Oetzthales mit dem Hochjochgletscher (links), dem Hintereisferner (in der Mitte) und dem Kesselwandferner (rechts oben). Nach der Natur gezeichnet von K. Schmetzer (1891)."

These records showed various fluctuations, but from 1850 onward a general trend of recession of glaciers in the Alps is observable. This trend has experienced a strong increase in the last 50 years, causing concern for the fast change in the landscape, the destabilisation of the rock walls once supported by the melting glaciers and the alteration of the discharge and hydrology of mountain ranges.

Fig.5. Temperature rise in the Alps and length loss of the glaciers of the Ötztaler Alps (western Austria) in the period 1900-2010. The valley glaciers with their tongues extending in the valleys showed the strongest retreat and degradation of the studied Austrian glaciers.

Sea-Level Highstand disproves ice-age CO2 connection?

The ice ages on Earth could be influenced by CO2 levels differently than previously believed. The study of speleotherms in the cave of Vallgornera situated on the Spanish island of Mallorca revealed that the polar caps were as small as today 81,000 years ago - despite lower CO2 levels.
A team of scientists of the University of Iowa has studied aragonitic and calcitic mineral deposits from five caverns situated; depending of the sea level - itself varying by the amount of “captured” water in ice caps up to 130m - the caves were inundated and different mineralogical deposition occurred.

The dated samples suggest that the sea level around 81,000 years ago was about a meter above the current value. "We have reconstructed the sea level with really high precision," says researcher Doral to the German newspaper “SPIEGEL ONLINE”.Co-author Bogdan Onac from the University of South Florida explains that Mallorca is ideal for this kind of research because tectonically stable and the observed variations should be “true” variations of sea level, not falsified by geological movements or isostatic rebound.

If the sea level 81,000 years ago was actually where the researchers suggest, an interesting problem arises: it doesn’t support the calculated 100.000-year cycle of glacial advances. Also it contradicts the direct ice-CO2 connections - despite low CO2 concentrations, and weaker greenhouse effect, the ice caps on earth were not as great as previously tough, and in dimensions comparable to modern conditions.

So are climate denialists right, and is there no such thing as anthropogenic greenhouse effect?

No, the authors want to take the results in a scientific context: the research doesn’t make claims about the global temperature during this time, only about the possible ice volume, and the amount of ice is not only controlled by temperature, but also for example by insolation of the sun, stronger 80.000 years ago then today. "What happened 80,000 years ago, is not the same as what happened today," said Onac.

REFERENCES:

DORALE et al. (2010): Sea-Level Highstand 81,000 Years Ago in Mallorca. Science Vol.327(5967): 860 - 863

Mission CryoSat-2

Source: Project Cryosat and Cryosat-2

The ice in the polar regions play a crucial role in earths climate, but the quantification of the ice and measuring it's change trough time is difficult.
Satellite images provide a good tool to determinate the area, but the thickness can only measured on single points by costly drilling trough the ice. New generation satellites, like the American "Icesat" use RADAR technology to determinate precisely the ice thickness, but snow cover and water are still a problem, and can distort the measurements. After the failure tof the European Space Agency to send a new generation satellite - Cryosat (crashed only few seconds after the start in 2005)- in the orbit, now his brother - Cryosat2- is almost ready.

In December the satellite will leave Munich (Germany) to be transported to the Kazakhstan spaceport Baikonur, from where it will be send in February 2010 with a modified rocket (a former atom weapon carrying Dnepr model) in space.
With a new RADAR-altimeter ("Siral") Cryosat2 will take 20.000 measurements per second in the next three years with an unequalled precision, and be able to determinate changes of thickness in ice of only few centimetres.

Meanwhile reports of Canadian researches under David Barber (University of Manitoba) confirm the receding trend of the ice cover in the Arctic. On 12 September 2009 the ice covered 5,1 million square kilometres, only 2007 and 2008 the area was lesser compared to the mean value of the 30 years of satellite measurements. Compared to the long term observed between 1979 and 2000, the remaining actual ice cover is also 70% of the former area, the area of long lasting ice diminished from 90 to 17%.
Not only the area is declining, also the thickness is inferior, in some areas the thickness diminished from 10m to 2m. The thinner ice is more fragile, and can not resist wave movements or storms.

Biologists are concerned about the status of the polar bear, with a valued population of 25.000 animals: the ice is in vast regions to thin to be used by the animals to hunt, and the sea freeze later in the year.
In the area of Churchill, in the Canadian province of Manitoba ,the biologist Ian Sirling (Canadian Wildlife Service) observed a possible related fact - an increasing of cannibalism events from elder on younger animals.

No more ice on Kilimanjaro ?

After Thompson et al. 2009, interview to Dr. Thompson mp3

The glacial record in Africa is restricted to the highest peaks of this continent, mainly to mountains of east Africa: Mount Kilimanjaro (5895m), Mount Kenya (5.199m), the Ruwenzori (5.119m) and on the northern margin of Africa in the High Atlas. Traces of two Pliocene-Pleistocene glaciations have been found on Mt Kilimanjaro, the oldest of which have been dated to about 2.0My (OSMASTON, 2004). Younger, in part uncertain glacier advances are dated to 1,0My, 0,4My and during the last glacial maximum (20.000y). Today three main glaciers persist on the summit of the volcano - the Northern Ice Field (NIF), the Southern Ice Field and the Furtwängler Glacier; some smaller glaciers are distributed on the slope of the mountain. Cores taken from all three glaciers showed that the ice cover on Kilimanjaro persisted for at least 11.700 years.

Isotopic record of oxygen isotopes from the Northern Ice Field (NIF), after THOMPSON et al. 2002

In modern times the dramatic loss of Kilimanjaro´s ice cover has attracted global attention, and has been a symbol for changing climate in Africa in popular media. The glaciers have considerable lost volume and surface, from 12,06 square kilometer in 1912 to 2,6-2,5 square kilometer in 2000. In the last 7 years ulterior 26% of this remaining ice are gone, leaving 1,85 square kilometer back. But not only the ice covered surface - easy to observe by aerial photographs - diminishes, but more important the glaciers are rapidly thinning, up to 0,5m thickness loss per year. This glacier mass lost is harder to determinate (mostly by measuring with stakes you got only punctual data) but crucial to understand the glacier balance.
If this melting rate persists, until 2022-2033 there will no more glacier ice left on the summit.

The widespread retreat of glaciers in Africa suggests a common driver, and not only local factors like deforestation, land use or humidity change on the slopes of Mount Kilimanjaro. The long record that this ice fields provided, demonstrate that for more then 11.000 years ice persisted without essential melting or mass lost, even during the end of the humid phase in Africa and change to more drier climate and subsequent droughts (p.e. 4.200 years ago). This seems to minimize the influence of changing precipitation on the glacier mass balance, and emphasizes changing in the temperature regime on the summit of the mountain.

References:

EHLERS, J. & GIBBARD, P.L. (2007): Glaciations. In (ed): ELIAS, S.A. (2006): Encyclopedia of Quaternary Science. Elsevier : 290-300

OSMASTON, H. (2004). Quaternary glaciations in the East African mountains. In J. Ehlers and P. L. Gibbard (eds): QuaternaryGlaciations - Extent and Chronology, Part III: South America, Asia, Africa, Australasia, Antarctica: 139-150.

THOMPSON, L.G. et al. (2009): Glacier loss on Kilimanjaro continues unabated. Proceedings of the National Academy of Sciences.

Glacier Erosion

Forms of glacial erosion represent some of the most widely distributed and recognizable indicators for past glacier extent. The discovery that polished rock surfaces were formed trough glacier abrasion, and the subsequent mapping of this feature on valley floors very distant from recent glaciers, was vital for the support of the "glacial theory" in the mid-1800s by the geological community.

The glacial striations of Le Landeron on Lake Biel, visited by the participants of the excursion of the Société Géologique in 1838, in a representation of Agassiz's work Etudes sur les glaciers of 1840.

Abrasion is the process of (frictional) wear, produced by surface rubbing against each other, and is achieved in the subglacial environment by sliding of debris-charged ice across the rock-bed.
Roches moutonées are the classical example of subglacial bedrock erosion, with abrasion dominating on the upstream (stoss) side and plucking (material pull off) on the lee side. This results in a highly unsymmetrical form, with a plain, upward side and a step to vertical termination.


To be continued...

Geologists Who Say "Nye"

Roches moutonnées of the last glacial maximum seen by the "Geotope Fischbach" (Bavaria) with Nye channels (after a British physicist) - subglacial channels eroded by meltwater under high pressure in the limestone formation of the "Wettersteinkalk".

In warm-based glaciers, also called temperate glaciers - with the bottom near or slightly above the freezing temperature, water flows in or on the bottom of the glacier forming subglacial streams in channels, that finally join at the snout, forming a glacier outlet.

There are three types of subglacial channels, depending on such factors like glacier movement, bedrock topography and lithology:

N-channel or Nye-channel: incised in the underlying bedrock.

R-channel or Röthlisberger-channel: incised in the ice (and so not found in "fossil" form).

C-channel or Clarke-channel: partly incised in the bedrock and ice, a combination of the formerly mentioned types.

Trafoi glacier (1867)

Landscape at Trafoi in 1867, by the austrian artist Anton Schiffer (1811 - 1876).

Austrian glaciers still have fever

The measurement of glacier lengths carried out by the Austrian Alps Association (Österreichischer Alpenverein) showed a “strong degrade of the glacier-tongues” in the past years. During the period between 2007 and 2008, 10 of the total 94 controlled glaciers shortened between 33 up to 49m. “These valley glaciers still suffer from the extreme mass lost in the year 2003” explains the author of the study and glacier expert Prof. Dr. Gernot Patzelt.

From the studied glacier, 88 have lost length, 8 remained stationary and only 4 have gained moderate length (ca. 5m), this results in a mean length loss for the Austrian glaciers in the measurement- season 2007-08 of 12,8 meters, slightly inferior to the precedent years (22,2m, where all observed glaciers retreated).
The mean length reduction in the past 10 years resulted to be 14m per year.

The wet and cold weather until July 2008 prevented first the ice melt, but then a pronounced warm period at the beginning of August caused a strong degradation of the snow cover.

Length loss of the glaciers of the Ötztaler Alps (western Austria) in 10m intervals. The valley glaciers with their snouts extending in the valleys showed the strongest retreat and degradation of the studied Austrian glaciers, length gain could only observed by 4 glaciers in the central Tauern Alps (eastern Austria).

Swiss glaciers still have fever

The published results of length variation of Swiss glaciers confirm the general recession trend of glaciers in the Alps observed since 1980. 79 glaciers showed a retreat in 2008, only 5 a small advance (with length gain between 5 and 10m), and 2 remained stationary. Notable the length loss of the Eiger glacier with 225m and Gorner glacier with 290m.

Legend: blue triangle: advancing glacier, yellow: retreating glacier, grey: stationary glacier

Legend: Percentage of advancing Swiss glaciers (blue), stationary glaciers (green) and retreating glaciers (red) in the last 100 years.

References:

Gletscherberichte (1881-2008). "Die Gletscher der Schweizer Alpen", Jahrbücher der Expertenkommission für Kryosphärenmessnetze der Akademie der Naturwissenschaften Schweiz (SCNAT) herausgegegeben seit 1964 durch die Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW) der ETH Zürich. No. 1-124, (http://glaciology.ethz.ch/swiss-glaciers/).

Volcano-Ice Interactions

A lahar is a general term for a type of rapidly flowing mudflow / landslide composed of an water-satured (at least 40-80 weigth% ) mixture of volcanic deposits. The term 'lahar' originated in the Javanese language of Indonesia, meaning “wave”.

Lahars can have four main causes:

-Snow and glaciers can be melted during an volcanic eruption
-(Crater-)Lakes breakout, triggered by collapse of natural dams (lava flows, ash deposits etc.)
-Heavy rainfall, caused by precipitation from eruption cloud

-General remobilizing of volcanic deposits without implications of eruptions

Considering mainly the first category –two main premises have to be considered. The volcano, if he is not located in the Arctic or Antarctic realm, must be high enough to possess a snow cover or enable glacier formation, and he must be active in historic times.

Several mountains in the world, including Mount Rainier, Mount Shasta and formerly Mount St. Helens in the Cascadian Range, Mount Ruapehu in New Zealand, Popocatepetl in central Mexico, different Volcanoes in the Andes (like Nevado del Ruiz) are considered particularly dangerous due to the risk of lahars.

The lahars from the Nevado del Ruiz (5.321m a.s.l.) eruption in Colombia in 1985 caused the Armero tragedy (13.11.), which killed an estimated 23.000 when the city of Armero was buried under 5 metres of mud and debris. Pyroclastic flows melted ice and snow at the summit, forming four thick lahars that rushed down several river valleys. Historic lahar-events date back to the 16th century.

Popocatepetl volcano (5450m a.s.l.) is probably the most active volcano in central Mexico, and threatens more than 40 million people livingin the Mexico City area. The principal danger is rappresented by laharic events, that following the main river, can reach zones distant up to 15km from the volcano. The Ventorillo Glacier, located on the northern flank of the volcano, is the main source of meltwater during eruptions. Popocatepetl got active after 50 years of quiescence in 1994, and on 31. June 1997 a lahar with an estimated volume of 1x10^7m^3 formed from the tongue of the glacier and deposited 3.3x10^5 m^3 of material in the circumstandig river valleys.

Mount Ruapehu, or just Ruapehu (consisting of three major peaks Tahurangi, 2.797m, Te Heuheu, 2.755 m and Paretetaitonga 2.751 m), is the largest active stratovolcano at the southern end of the Taupo Volcanic Zone in New Zealand. The North Island's major skifields and only glaciers are on its slopes.
In recorded history, major eruptions have been about 50 years apart, in 1895, 1945 and 1995-1996. Minor eruptions are frequent, with at least 60 since 1945. Some of the minor eruptions in the 1970s generated small ash falls and lahars that damaged ski fields.

Between major eruptions, a crater lake, damned by volcanic ash and rocks, forms, fed by melting snow. The collapse of this natural dam, blocking the outlet of Mount Ruapehu´s crater lake, caused in the past (and presumably will cause in the future) catastrophic lahars.

Fresh lahar channels scar Ruapehu's eastern slopes (27.03.2007, wikipedia)

December 24., 1953, a lahar destroyed the Tangiwai rail bridge, causing the derailment of a train, and the dead of 151 of the 285 people aboard the train- the worst train accident in New Zealand. Until then, the danger of lahars was underestimated in the public view, and only after the tragedy a monitoring program was installed on the volcano.
The eruption in 1995 closed the ski season for that year and was followed by some more eruptions in 1996. During March 18., 2007 a lahar, with estimated 1.4 million cubic metres of mud and rocks, was documented by a film crew.

The active rockglacier at Hohe Gaisl - implications on genesis

Active rockglaciers are less common in the mountain ranges composed of carbonatic rocks, such as the Northern Cretaceous Alps ort he Dolomites, even if here more than lithology probably the minor mean elevation plays a role.
Although few active rockglaciers are present in the Dolomites, they have never been studied in detail.
One studied rockglacier is located in the “Gletscherkar (glacier cirque)” on the north-eastern side of the Hohe Gaisl (3146m). The rockglacier lies in a deeply incised cirque, surrounded by steep walls composed of upper Triassic dolomite and limestone.

Fig.1. Air photos and digital terrain modell of the Hohe Gaisl mountain group with two active rockglaciers in the north-eastern cirques (Autonomous Province of Bozen/Bolzano - South Tyrol)

Fig.2. View to west on the Hohe Gaisl mountain group with two active rockglaciers in the north-eastern exposed, deeply incised cirques. The visited rockglacier can be found in the right cirque (north).

Debris of the rockglacier is mainly derived from a prominent, NW-SE-trending fault, along which the bedrock is intensively deformed. The rockglacier is 850m long, 300-550m wide and covers an area of 0,3 square kilometres. The rockglacier extends from an altitude of 2340m at the front to about 2500m. The eastern lobe shows well developed surface topography of transverse ridges and furrows. The surface is coarse grained and varies from place to place, manly constituted of poorly sorted gravel and sand, huge boulders are missing, great blocks exceeding 1m are rare.

Fig.3. View to west on front of the "Gletscherkar" rockglacier.

In the upper part massive ice is exposed during the summer months at several places below a less than 1m thick debris layer. The ice is coarse-grained, banded, and contains thin, fine-grained debris layers parallel to the banding. Rarely larger clasts occur within the ice.
During the melting season small thermokarst lakes may be developed on the upper part of the rockglacier.

Fig.4a. Ice-exposure on the rockglacier (15.09.2007).
Fig.4b. Fine-grained debris layers parallel to the banding in the ice (15.09.2007).

Georadar measurements provided information on the internal structure and thickness of the rockglacier. The data indicate that the rockglacier has a total thickness of approximately 25m. In the lower and middle part the debris layer is 3-5m thick. Below the debris layer numerous, well developed reflectors are visible indicating the presence of shear planes in the frozen body of the rockglacier, which according to ice exposure in the upper part is composed of coarse (glacier) ice with numerous thin debris layers parallel to the banding. A thin sediment layer (?lodgement till) may be present at the base of the rockglacier.

Internal structure and ice exposure clearly indicate that the rockglacier in the Gletscherkar developed from a debris-covered cirque glacier. It is suggested that the glacier has developed from a small cirque glacier during retreat trough inefficiency of sediment transfer from the glacier ice to the meltwater. The presence of a cirque glacier at Gletscherkar is documented in the older literature and on older maps, for example on a topographic map published in 1902 (FREYTAG 1902).

References:

KRAINER, K. & LANG, K. (2007): Active rock glaciers at Hohe Gaisl (eastern Dolomites). Geo.Alp 4, 127-131
LANG, K. (2006): Geologie des Hohe Gaisl Massivs (Pragser- und Ampezzaner Dolomiten) unter besonderer Berücksichtigung der aktiven Blockgletscher. Unveröff. Diplomarbeit, Institut für Geologie und Paläontologie Leopold-Franzens-Universität Innsbruck, 170S.
SHRODER, J.F.; BISHOP, M.P.; COPLAND, L. & SLOAN, V.F. (2000): Debris-covered glaciers
and rock glaciers in the Nanga Parbat Himalya, Pakistan. Geografiska Annaler 82(A):
17 - 31

Glacier Change

Waxeggkees (Zillertaler Alps) ca. 1900-1906 and 2006

Panta rhei

Shear bands in the tongue of the "Gurglerferner", a glacier in the Ötztaler Alps (Italy-Austria), dipping from nearby flowparalell to vertical, to cross the surface of the glacier perpendicular. This feature demonstrates that in the movement of glaciers an important role plays even brittle deformation

Glacier mass balance values for the year 2006

Preliminary mass balance values for the year 2006 are now available from more than 80 glaciers worldwide. The continuous mass balance statistics below are calculated based on the 30 glaciers in 9 mountain ranges with long-term data series back to 1980. The statistics for the year 2005 are based on 29 glaciers from 9 regions, and the preliminary values for the year 2006 result from 25 glaciers in 7 regions. The related statistics and figures will be updated as soon as the missing data becomes available.
The average mass balance of the glaciers with available long-term mass balance series around the world continues to decrease, with tentative figures indicating a further thickness reduction of 1.4 m w.e. during the hydrological year 2006. This continues the trend in accelerated ice loss during the past two and a half decades and brings the total loss since 1980 at more than 10.5 m w.e.

Tracing glacier wastage in the Northern Tien Shan

Tracing glacier wastage in the Northern Tien Shan (Kyrgyzstan/Central Asia) over the last 40 years

The status and dynamics of glaciers are crucial for agriculture in semiarid parts of Central Asia, since river flow is characterized by major runoff in spring and summer, supplied by glacier- and snowmelt. Ideally, this coincides with the critical period of water demand for irrigation. The present study shows a clear trend in glacier retreat between 1963 and 2000 in the Sokoluk watershed, a catchment of the Northern Tien Shan mountain range in Kyrgyzstan. The overall area loss of 28% observed for the period 1963–2000, and a clear acceleration of wastage since the 1980s, correlate with the results of previous studies in other regions of the Tien Shan as well as the Alps. In particular, glaciers smaller than 0.5 km2 have exhibited this phenomenon most starkly. While they registered a medium decrease of only 9.1% for 1963–1986, they lost 41.5% of their surface area between 1986 and 2000. Furthermore, a general increase in the minimum glacier elevation of 78 m has been observed over the last three decades. This corresponds to about one-third of the entire retreat of the minimum glacier elevation in the Northern Tien Shan since the Little Ice Age maximum.