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Eagerly awaiting your next! Items as small and fragile as atlatl darts from 10,000 years ago have been found. This is the most exciting subset of archaeology being discussed in Northern Ontario at this time.


Whats the word up north if you have time to share? I knew that 10kya stuff had turned up and it has implications for theories of human migration but I don't know much more than that.

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Don't eat the brownish-black snow.

People now and in the prehistoric era go (went) into the mountains for a lot of reasons, not limited to: trade, hunting, quarrying obsidian, flint and other lithic resources, finding surface metals, gathering of foodstuffs and medicines, acquiring status & luxury goods including furs and feathers, for reasons of religion and wonder, and the transhumant. To do these journeys, alpine travelers from the ancient to the modern invented appropriate gear for mountain travel. Here's a very brief blog post that gives an overview:

What I like about this is that there's some mention in there that Coast Range alpine environments were and are extreme and in the modern era we would expect persons undertaking such a journey to be experienced and prepared; the message to us is that the Native alpinists of the past were in fact properly geared-up adventurers and explorers of great skill.

In the late 1990s two hikers, Kristin Kuzyk and her wildlife biologist husband Gerald, went into the mountains of the Yukon tracking Dall sheep. Their walk was interrupted by the powerful stank of caribou crap. What they found was a patch of melting ice with a slick of decomposing manure oozing out of it. Caribou hadn't been seen there for three quarters of a century. Later, Kuzyk and a colleague turned up a 4000 year atlatl, and kicked off the discipline of ice archaeology.

It was a new discipline because scientists hadn't really thought the 1991 discovery of Ötzi all the way through. Finding the mummified tyrolean traveler was a one-off, an amazing gift of chance, and archaeologists didn't put it together that human use of alpine resources on or near the ice might have been regular, intense, and focused enough that – combined with glacial retreat – it would merit a programmatic search for likely sites. In short, getting to these ice patches is a big freakin' pain in the butt to go someplace cold, dangerous and uncomfortable, so why would anyone have gone there, and who wants to stumble through the mountains on the off-chance of finding another Ötzi?

Hunting is and was of course a big reason for men and women to be at altitude, and hunting is the reason ice patch archaeology pays off. I'm terrible at hunting. I hate bushwhacking, and I'm bad at being patient so my preferred method is to find a likely spot, put down the rifle, and pick up a book. Hunters ancient and modern agree with me that clowning around in the woods is a bad way to get the job done and a better way is to find where the game is going to be, and go straight there.

I'm sure you all are on board with the idea that the north in summer is godawful for flies and mosquitoes. Caribou and reindeer concur, so what they do is haul on up to ice patches in the daytime to dodge the heat and wait out the clouds of biting insects.


From the Prince of Wales Northern Heritage Center.

Ancestral First Nations hunters took one look at that and decided it was a vast, convenient chest freezer full of walking meat. Because these patches concentrated hunters, they concentrated lost or discarded hunting gear.



The summary below draws on an array of recent publications by Canadian researchers and is illustrated with resources from Prince of Wales Northern Heritage Centre who approve use of their material for educational purposes. They have a very neat interactive exhibit for young people (linked below). For those of you who want the academic material they have an extensive bibliography (go to the menu) detailing current ice patch research for both North America and the world.

Map of the study area:


Figure from Multidisciplinary Investigations of Alpine Ice Patches in Southwest Yukon, Canada: Paleoenvironmental and Paleobiological Investigations. Richard Farnell lead author.

Like upthread, ice patches are distinct from glaciers; they are static or mostly so, and do not cycle through their ice on century time scales. They frequently form in north-facing lee hollows or other places where snow drifts & accumulates, then compacts to ice on a permanent, semipermanent, or empheral basis. Because they are static, their layers and their contents are less deformed by flow, and they have the potential to preserve a clear chronological record. Their existence is delicate: too much accumulation and you have an active glacier. Too little and the patch melts out. However, they are also robust: the patches have selfregulating feedback features. Organic material in the bottom two crap layers of the Granger patch has been radiocarbon dated to 8000 and 8300 cal BP.

Arrowheads and ceramics are durable and relatively plentiful; intact atlatls, darts with points, fletching and binding still attached, baskets, leather, textiles, faunal remains – anything with an organic component – is much more rare and exciting. Some ice patch finds are quite finely made and beautiful, like this copper-headed dart the point of which is worked from a nugget of high quality surface copper and fixed to a barbed bone shaft. Found in the Wrangell-St. Elias NP, it has been dated to ca. 1600 cal BP.


E. James Dixon of the NPS via the Northwest Coast Archaeology blog

Like Terry mentioned, the oldest objects recovered so far in North America are darts dating back to 10000 cal BP. Artifacts with organic components require unusual conditions (desert, bog, ice, etc.) to persist and must be found and conserved within months, weeks, or even days when removed or exposed from the preserving matrix. There is time pressure for this work.

Fortunately caribou would visit patches regularly and in number, and herds would return to favored patches frequently. And caribou like to crap. They crap a lot in the snow. The dark ring of caribou crap is easily spotted from the air, as at this ice patch photographed in 2009 – although in Alaska patches are so potentially many and flight hours so few, there has been development of GIS software to identify likely candidates for aerial survey. Once a likely site is found, it is monitored for emerging finds regularly.



At likely patches, archaeologists walk the perimeter CSI'ing around for stray ballistics and anything else lost or discarded by ancient hunters. The caribou crap is a fertile (heh) source of data, as is the ice core. Cores can preserve a stratigraphic signal in the ice and capture dust & pollen; the caribou crap itself can be preserved as a seasonal layer or even be frozen as distinct individual pellets. All this material can be radiocarbon dated and the manure contains remains of the animals' diet as well as hair and other sources of genetic material. A madman billionaire could, if he or she wanted, use ice patches as the basis of a Mid-Holocene Park full of prolifically [email protected] ancestral caribou.


Pictured are Thomas Meulendyk and Brian J. Moorman of the University of Calgary. Photo via PWNHC.

Ice patch archaeology therefore in many ways involves working in conditions directly analogous to the back yard of every dog owner in the Great-Lakes & OHV forum come springtime.



As the Canadian research groups explain, caribou $h!t stratigraphy produces a well-dated record of local snow accumulation, climate conditions, ecology, and animal behavior. In this figure by Farnell and company showing the radiocarbon dated poop layers of three Canadian reference sites, we can see that the southern Yukon experienced a period of cooler temperatures and / or increased precipitation in the early Holocene followed by a near 2000 year interval during which there was no net ice accumulation or in which that ice was condensed by melting (or both), followed by 5000 years of a mostly stable cool-wet regime. Unlike glaciers, ice patches are small and can react rapidly to their regional climate and indeed their weather -- to a few bad years or a bad summer. Given that, note the necessary boundaries of ice patch behavior which limit the range of regional climate variability during the 2000 year icemanure hiatus: the patch neither accumulated so much ice as to start moving nor experienced catastrophic melt intense enough to wreck the underlying paleoice-and-crap horizon. Further, this is not relict Pleistocene ice; it is early Holocene ice on top of early Holocene poop. That does not, however, preclude there from having been previous icy caribou turd factories at these locations before the existing ones.


Figure from Multidisciplinary Investigations of Alpine Ice Patches in Southwest Yukon, Canada: Paleoenvironmental and Paleobiological Investigations. Richard Farnell lead author.

These findings combined with other paleobiological research and taken in general agreement with other paleoclimatic reconstructions of the Pac-NW indicate a relatively stable climate in this region on multimillenial timescales from the middle Holocene. At present these ice patches are, of course, melting rapidly. This is the patch above photographed again one year later in 2010. When the patches melt down, crap horizons from layers above mix onto / in with layers below, forming a jumbled “palimpsest” “poop puzzle” or manure “super layer”; exposed artifacts are threatened with rot, disintegration, or destruction via animal (in some places, caribou trampling). Ice patch archaeology is a new discipline but one with a potentially short lifespan as it faces the imminent loss of this unique record of human and animal life during the Holocene.



As of 2011 the above patch scorched out completely, erasing a landscape feature which had been present and more or less stable since ca. 3500 cal BP.

Lastly, Archaeologists in the USA (Front range e.g.) and in Canada have found that bison used make use of ice patches in a similar fashion. Therefore it can truly be said I just sold you a huge line of bull$#!t

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Dairy Queen cakes of caribou crap are great and all, but they're nowhere near as cool as Neolithic ice mummies and complete hunting assemblages. North America is shy on ancient ice mummies; it has one glacier body of note, Long Ago Person, a First Nations alpinist who died ~300 cal. BP above the tree line in the mountains in British Columbia. He was found with his gear, but due to the movement of the glacier, he was thoroughly dismembered.

The most famous ice mummy is probably Ötzi, or, more formally, “Similaun Man”. You all probably know this, but to recap: In 1991 two German hikers came across his upright, ice-embedded torso somewhat below the most often-traveled touring route.

Because I like pictures here is one of the setting, place of discovery marked in red:


… and the body. Spoiler alert in case you don't care to see human remains.


Both images hosted on Wikimedia.

As you can see, that's one heck of a mummy. His internal organs and stomach contents, though shrunken and dessicated, were preserved. In fact, he was so well preserved that his cause of death could be assigned to the fact that he was shot in the back with an arrow – arrowhead still embedded – and bled out. The truly remarkable thing about Ötzi is that archaeologists recovered his gear in various states of intactness: probably all of it. Tunic, leggings, cape, hat, boots, belt, bow, arrows, quiver, fletching kit, firestarting materials, the whole deal. Radiocarbon dated to 5300 cal. BP.

I mentioned upthread that when it melted out of the ice, it was to that point the only intact prehistoric longbow, well, it was until one of the SAR crew snapped it in half to use as a digging stick. His copper axe also took a little walksie before being returned once it was realized how important of an archaeological find the body was. Here's one half of the bow:


Excerpted from the appropriately named Baugh et. al, “Ötzi's Bow,” first published in the Bulletin of Primitive Technology.

A dozen years later in Switzerland's sunny Schnidejoch the next intact prehistoric bow melted out of the ice:


From the website,

… and a German hiker promptly absconded with it. After keeping it in his garage, or, you know “wherever” he brought it back to Bern in 2005 when the news broke about the importance of the Schnidejoch finds. Facebook ready:


From the Kanton Bern press statement.

Here's where the Schnidejoch is:


Map from

And what it looks like:


Excerpted from Hafner, Albert. "Archaeological discoveries on Schnidejoch and at other ice sites in the European Alps."

In addition to the bow, archaeologists turned up an accompanying quiver, arrows, leggings, a shoe, and assorted pieces of leather. All dated to ~4600 cal. BP. The birchbark bow case:



… So much gear in fact, and so complete, that the archaeological team thought they must have found the last resting place of another ancient alpinist. A “Schnidi” to go with “Ötzi”, on the reasoning that only in extremis would an alpinist offload & dsicard his or her survival equipment. AFAIK no accompanying body was ever found.

OK, so here's the point of all this from a paleoclimatic perspective. I mentioned in the previous post that these organic artifacts: mummies, faunal remains from hunting and butchering, leather, textiles, basketwork, wood – don't last long outside their preserving matrix. When Ötzi first emerged from the ice, and in light of the worry the Austrians and Italians had in stabilizing the mummy, it was argued that everyone's favorite Tyrolean murder victim had been buried by snow immediately after death, and that he had remained continuously covered in the intervening 5000 or so years.

In a recent overview of the topic, Rachel Reckin asks “well how long do these remains actually last?” She points out that there aren't any experimental studies on the preservation or durability after exposure of these kinds of remains, probably on account of there aren't that many of them to begin with and most archaeologists are more concerned with the challenges of immediate conservation rather than doing experiments on their precious ice mummies.

The detailed CSI work on Ötzi suggests that in fact he: 1. sat in a stiff, dry wind for a while, 2. was covered by snow and ice, which 3. melted such that he was immersed in cold water for some weeks and then 4. re-froze. They get this from his “freeze-dried-then-dunked” character and the fact that his reed cape had come apart and was evenly distributed across all the other objects since recovered. This happened sometime between his death and ~3000 cal BP based on the intact stratigraphic layer with organic materials emplaced immediately above.

Ötzi's resting place was, like the ice patches mentioned above, one of those protected places that gathered enough accumulation to remain more-or-less permanent, but not so much it started to move as a glacier. Non-glacial perennial land ice accumulates in a variety of ways depending on how its situated, and is maintained by stabilizing topographical and microclimatic features:


From Glazirin and crew, “Stability of drjfting snow-type perennial snow patches

… And they melt out in ways particular to their setting. It might “slice out” like this ridgeline “minature ice cap” at the Murtel-Corvatsch ice crest in the eastern Swiss Alps


Photo credit as in the image.

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… And it melts out in ways particular to its setting. It might “slice out” like this ridgeline “minature ice cap” at the Murtel-Corvatsch ice crest in the eastern Swiss Alps


Photo credit as in the image.

… which in the case of artifact-bearing ice patches as in the Yukon or Norway (not exactly the same setting but the M-C radio mast site has a very clear picture), in years of intense melt might reveal objects not quite in reverse chronological order, but across a range of eras. The ice sites in Norway have also been tunneled and show angular uncomfortities and other fun geologia. So from the Lendbreen glacier in Norway, researchers have recovered blinds and traps from a 1000 cal. BP hunting camp, a nearly intact(!) Roman-era sweater from 1700 cal. BP, and a leather shoe from 3000 cal. BP. The ancient wooly sweater has a nice diamond pattern:



From the History Blog.

At the Schnidejoch as well, the age range of artifacts is quite wide, ranging from 6500 cal. BP to 1000 cal. BP. The artifacts there were recovered from near bedrock with no discernable stratigraphic arrangement:


Excerpted from Hafner, Albert. "Archaeological discoveries on Schnidejoch and at other ice sites in the European Alps."

… raising the question of whether the Great Melt of 2003 slagged several stratigraphic layers in one big push, whether it compacted a few marginal lag layers, whether periods of surface melt concentrated artifacts in hollows, or whether in the last throes of the ice patch the darker artifacts melted downwards like a penny in a snowbank. Hafner argues on the basis of the large swath of recovered leather that ice coverage must have been continual since 4600 cal BP; Reckin would demur. I would too if my opinion counted, based on the differential sun bleaching identified on the Schnidejoch artifacts which were found on northern-vs.-southern exposure. At any rate, the answer to Reckin's question is constrained by what conservators can tell us and what experimental evidence we do have from e.g. the body farm: textiles and leather tanned with pre-modern methods turns to glop (if wet) or dust (if dry) within weeks. Mummies, especially small animal mummies, can probably take brief exposure, but not a lot. The takeaway for cognoscenti who want the details is that these recovered articles and remains were likely “more or less continuously” covered since they were lost or discarded.

What's neat, IMO, is what the age distribution of artifacts recovered in the European Alps might tell us about prehistoric human use of alpine resources and travel routes. Martin Grosjean and Albert Hafner observed that artifact finds coincided with eras of glacial retreat, and eras with no recovered objects coincided with periods of glacial advance. They argued that the advance and retreat of the glacier associated with the Schnidejoch ice patch could (given how narrow the pass is) essentially lends the pass a binary open/closed character for human travel:


Excerpted from Hafner, Albert. "Archaeological discoveries on Schnidejoch and at other ice sites in the European Alps."

Here is their data incorporated with a broader regional view of archaeological data and glacier advance / retreat.


Rachel Reckin, “Ice Patch Archaeology in Global Perspective”

Ultimately, we see that from the stratigraphic signal amenable to radiocarbon dating preserved by coherent caribou crap layers is the easiest path to establishing the chronology of periods of max temp / min precip. Still, when sites such as the Schnidejoch melt with near completeness, or when the Yukon manure patches slag out entirely, we can argue with some confidence via the disappearance of landscape features formerly stable for 4- or 5000 years that it is now as warm as or warmer at these locations than it has been since the mid-Holocene.


From Tom Andrews, “NWT Ice Patch Monitoring Project” newsletter update

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Short: humorous title coincidence in this post from Mauri Pelto "lake no lake"

Retreat of Lake No Lake Glacier Junction, Juneau Icefield, British Columbia

Lake No Lake is a glacier dammed lake that periodically drains under the retreating Tulsequah Glacier. Canadian topographic maps indicate that three glaciers coalesced to fill this valley: Tulsequah, No Lake East and No Lake West. By 1984 when I had a chance to see this lake had formed while working on Tulsequah Glacier. Here we examine the retreat of the three glaciers that has led first to lake formation and now to a reduction in lake size from 1984-2013.

Next, it can't be said enough that concern about snowpack and alpine ice are frequently water management concerns.

jfleck on recent research about same:

sublink on implications for hydrology & allied science

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Here is another neat thing that turned up. S-Central Europe got two powerful Föhns this winter in Feb-Mar, and the wind brought with it a nice haul of dust and sand from the Sahara. Here clearly seen as two dark layers in the snowpack. Pics from the ZAMG (austrian NWS/USGS) glacier survey

This is what it looked like plastered all over the ZAMG observatory @Hoher Sonnblick

Nov-Apr also made for exteme regional differences in precip across the Alps, with the northside rather dryer, southside wetter:

... Flipped in May with recordsetting precip (beating in some locales an instrumental record going back to 1820!) north of that same line

For the melt season this generally says the glaciers of the Eastern Alps started with a meaningful cushion of pack.

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Thank you for sharing that article.  I confess I had no idea that Costa Rica once had glaciers.



Mexico still has them as well as a handful of equatorial places but they'll be going the way of the Costa Rican glaciers before too long.

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Mexico still has them as well as a handful of equatorial places but they'll be going the way of the Costa Rican glaciers before too long.


Michigan used to have glaciers.

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Michigan used to have glaciers.

A fact well attested by the sound of furious slapping from innumerable GEOS101 undergads afflicted by clouds of biting insects during the annual ritual bloodletting known as fieldwork clinic at the Skeeter Sump Kettle Lake District

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4real tho alpine gets all the love when the Great Lakes has some of the most beautiful & startling glacial landscaping going on. I'll own up to being a sucker for the dissected karst topography of the Driftless Area with its consequent springs & caves, and ancestral Baraboo Range for their relative inexplicability & the feeling of fortune that something like the Devil's Lake gorge could persist.

One of those things like, hey, want to see where the Green Bay lobe of the last glaciation hit highstand? Where mighty continent spanning wall of ice stopped?

431-21: Devils Lake gorge, 3 miles south of Baraboo, WI. View looking south. This "L"-shaped river gorge across the Precambrian quartzite of the South Range of the Baraboo Syncline was cut previous to Upper Cambrian time when it was filled by marine sandstone. The whole area was deeply buried by Paleozoic marine sediments. When these were eroded away, streams that encountered the buried quartzite ridge migrated laterally and excavated the earlier quartzite gorge. When Pleistocene glaciers reached the eastern portion of the Baraboo Range, the terminal moraine of the Green Bay lobe blocked off the gorge and Devils Lake was formed. The tree-covered ridge this side of the lake is the northern moraine dam; the southern blockage is just around the left-turn bend at the other side of the lake. (30Jun98)

From here. Lots of other good shots thru the link:

Look at the right angle gorge, absolutely plain on topo:

Pics taken from this link sketch out the story in the caption above more explicitly

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Presently reading HERBERT MASCHNER AND OWEN K. MASON The Bow and Arrow in: Northern North America in Evolutionary Anthropology 22:133–138 (2013) which takes as its departure point some of the dynamics that go with technology choice for atl-atl & dart v. bow & arrow and what that means depending on what you're trying to get done with your deadly projectiles in environmental & resource context, context of other technologies, etc.

Adding it here because of the hunting kit stuff from upthread, and its a great idea for GLOHV crew's snow cams for when winter rolls round.

fn.55 Rasmussen K. 1931. The Netsilik Eskimos: social life and spiritual culture. Copenhagen: Gyldendalske Boghandel, Nordisk Forlag.

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Mauri Pelto posted up his summary of the 2013 WGMS tables for the latest BAMS State of the Climate

tldr: the glaciers are melting.

Figure 1: The mean annual balance reported for the 30 reference glaciers to the WGMS. And the cumulative annual balance for the reference glaciers 1980-2012.

In other news spent some time at the library could not find the historical reference I was looking for, but digging around in the Yearbooks of the Imperial and Royal Geological Institute 1850-1878 I saw a lot of beautiful watercolors and sketches, and this wonderful map of krakow:

Thank you for sharing that article. I confess I had no idea that Costa Rica once had glaciers.


Mexico still has them as well as a handful of equatorial places but they'll be going the way of the Costa Rican glaciers before too long.

I love them weird glaciers in odd places, like the glaciers of Nevada.

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This is pretty awesome: "The origin of Lake Vättern."

Keep reading until you get to the rebound description & estimated magnitude!


Out of curiosity speaking of Scandinavia anyone ever been to Lofoten?

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While its on my mind from the other thread and because weird glaciers in odd places are neat (click to read about the unwitnessed disappearance of South Africa's glacier)

-- here's an interesting case of revisions that could potentially result from a possible wx station screwup. I don't see that anything has come of this abstract in terms of papers under considerstion or any changes in the Meteo France data for Port-aux-Français or BEST's handling of its station changes, so maybe the identification of error was in error. Maybe someone who has the BEST raws could look at the metadata.

If nothing comes up I'm going to email the authors because I'd love to hear the story and hear what kinds of reinterpretation they think would be needed if they turned out to be right about the temperature time series:

Recent glacier retreat over Kerguelen archipelago (49◦S, 69◦E) derived from field data, satellite imagery and modelling

Deborah Verfaillie (1), Vincent Favier (1), Marie Dumont (2), Vincent Jomelli (3), Adrien Gilbert (1), Daniel Brunstein (3), and Yves Frenot (4)

(1) Université de Grenoble Alpes/CNRS, Laboratoire de Glaciologie et Géophysique de l’Environnement, UMR5183, Grenoble, France, (2) Météo France, CNRS/CNRM, GAME URA 1357, Centre d’Etude de la Neige, Grenoble, France, (3) CNRS, Laboratoire de Géographie Physique, UMR8591, Meudon, France, (4) Université de Rennes 1/CNRS, Ecosystèmes Biodiversité Evolution, UMR6553, Rennes, France

Situated in the Indian Ocean at 49◦ S, 69◦ E, Kerguelen archipelago represents a unique sub-polar observational site. Located at low altitude and on islands, the glaciers are particularly sensitive to oceanic and atmospheric variations (e.g. Poggi, 1977a,b; Vallon, 1987). The cryosphere on Kerguelen showed important fluctuations during the last 2 centuries (Frenot et al., 1993). After a small stable period until 1961, the ice cap showed a huge and extremely quick retreat, losing 20% of its surface during the last 40 years (Berthier et al., 2009). Relating directly this acceleration with the fluctuations of temperature and precipitation inferred from direct meteorological measurements is attractive and was generally performed (e.g. Frenot et al., 1993, 1997; Berthier et al., 2009). However, it was recently discovered that the drastic temperature change may be mainly due to changes in meteorological station characteristics in 1973 (Météo France, personal communication), challenging previous interpretation.

The analysis of field data collected on Ampere glacier since 2010 presented here provides a first approach in our aim to understand the recent rapid retreat of its cryosphere. In this area, short term mass balance data from previous studies (Vallon 1977a,b, 1987) were compared to recent mass balance measurements. The analysis revealed that the spatial distribution of SMB significantly changed in 40 years. Collecting spatially distributed data of the surface characteristics and ablation was crucial to better interpret our field data. Recent variations (from 2000 to 2012) of the equilibrium line altitude (ELA) of Cook ice cap derived from MODIS imagery confirmed that the ELA rose about 100m since 2000. Additionally, we analysed meteorological and reanalysis data over Kerguelen from 1950 to 2012, in order to assess the causes and processes involved in the retreat of the ice cap, and present additional SMB and ELA estimates from a simple positive degree-day model. We concluded that the parameter with the largest variation was precipitation, which was associated to a decrease in cloud cover. The direct impact of these changes was a rise of the 0◦C level that led to a reduction of the occurrence of solid precipitation at low el- evation. These retroactions demonstrate that Kerguelen’s glaciers are extremely sensitive to small climatic changes.

These results on glaciological processes of Ampere glacier are an important base to constrain modelling approaches to assess past, present and future ice cap variations. In this framework, regional scale simulations of mass balance processes over Kerguelen archipelago have been initiated with a downscaling scheme (SMHiL) and with the regional climate model MAR (Modèle Atmosphérique Régional).

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So upthread Coventry mentioned this:

All of the glaciers that we skied on have shrunk in size, wasting away with strongly negative mass balances by the end of the summer melt season in September. Stubai glacier is about 85% snow free by September, where it needs 70% snowcover, just to maintain equalibrium. The problem that alot of these glaciers have is that they are now located below the summer snowfall line and now get summer rain and melt instead of snow. If these glaciers cannot retreat to an equalibrium elevation, they are doomed.

Here's some more on the implications of that which is also an excellent opportunity to post cool maps and diagrams from Matthes' Geologic History of the Yosemite Valley (1930)

Because where this post is going requires a detour through Geology 101 which I promise has a point in the next post.

The cool map is spoilered because it is large.


The map is a good reminder of what alpine glaciers "are" AKA big ol' rivers of ice formed when the summer snow line drops far enough to allow annual accumulation of ice and snow. Get enough of it, it starts to flow downhill and its tongue pushes past the summer snowline. Below the summer snowline, the tongue ablates. So the classic view of the glacier we all got taught as kids (from the Yosemite webpage) depicts a balance between a zone of accumulation above, zone of ablation below:

And the relation between the two, roughly speaking, is the mass balance. When accumulation is greater than ablation, the glacier will advance or thicken. When ablation is greater than accumulation, it will thin or retreat. Lots of factors can contribute to either -- some of the glaciers that still persist in say the Pyrenees recieve important contributions from avalanche, while as we know from the Greenland thread, dust and soot can darken glacier surfaces and accelerate ablation. However, mass balance is often reduced to winter precipitation and summer temperatures.

Arriving at that cool Matthes map is essentially an exercise in matching various geomorphological evidences to topography to answer: how far down the valley did the glacier reach, and how much of the valley did the glacier fill, at what times, and in what sequences?

The Matthes USGS working paper diagrams this:

"FIGURE 22.—Longitudinal profiles of Yoesemite and Merced Glaciers in the El Portal (EP) and Wisconsin (W) stages of glaciation. The lake basins on the treads of the glacial stairway are indicated in black. The vertical scale is twice the horizontal."

"FIGURE 23.—Section across Tenaya canyon and the Little Yosemite, showing the highest levels reached by the Tenaya and Merced Glaciers during the earlier and later ice stages."

For the last few millenia in places like the Sierra or the Alps, much of that hangs on the identification of assorted types of moraine (lateral, medial, terminal, recessional...)

Moraines are of course what you get from all the rocks and crap a glacier scours out or carries downstream when the ice melts back. The wiki page says bulldozed, and I think bulldozed is right.

"The Mothership", a 3-mile wide terminal lobe of a glacier flowing down from the interior ice cap on top of the Byam Martin Mountains, Bylot Island, Nunavut. Note the dramatic terminal moraine "bulldozed" at the ice front.

One of the most dramatic moraine complexes is Norway's "Trollgarden" aka the troll wall, which is a couple kilometers long (pixs shamelessly snagged from GIS via and

So in building its foundation for the reconstruction of the glacial history of Yosemite, the Matthes paper treats an idealized version of this:

"FIGURE 17.—Idealized sketch of a glacier leaving successive moraine loops as it melts back. In the Sierra Nevada, where the glaciers carried relatively little rock débris, many of the moraines are of the sharp-crested, clean-cut type here portrayed."

"FIGURE 19.—Sketch showing in section lateral moraines such as are situated in tiers one above another on the north side of Little Yosemite Valley. The loose rock grains washed down from them accumulate to form sandy terraces between the crests"

This whole long post was in service of saying that this particular view of valley glaciers and the characteristic glacial landscapes they leave is very much a "clean cut" view whereby glacier recession is described by the dynamic, orderly movement of the terminus as the glacier seeks to retreat to a geometry where its zone of accumulation is a certain proportion to its zone of ablation as the summer snow line -- lets just say "equilibrium line altitude" or ELA, rises, leaving features such as terminal and recessional moraines.

But like Coventry said -- a lot of glaciers are now wholly below their ELA. What then?

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One example from the previous page came from a team including Luca Carturan of the University of Padova, showing mass balance, areal extent, and comparative photograph of the Careser glacier in the Ortler-Cevedale group as reported in their 2013 paper "Decay of a long-term monitored glacier: the Careser glacier (Ortles-Cevedale, European Alps)."

In their paper you can see how you have a glacier moving downvalley, fed by an accumulation basin,

In their paper we can see that first the tongue retreats, then the entire accumulation area progressively fragments by thinning.

Watch how the elevation craters across the entire glacier area, indicating progressive thinning of the ice body along with the appearance of outcropping areas of rock.

So glacier melt includes retreat of the terminus, but thinking of retreat solely in terms of the tongue receding doesn't well at capturing the next stage of glacier thinning -- where the whole ice mass is downwasting rather than backwasting.

Glacier recession over prominent topographic obstacles either apart from or in tandem with rapid climate change offers the possibility that large portions of the glacier tongue might become separated from the glacier body. No longer fed by the parent glacier, these separated portions of low- or no-ice flow can stagnate, and become "dead ice." This ice then melts out in place.

The following figure is from Vacco (2010) given below. The authors note that if movement of the ELA is small enough, the glacier can retreat across the obstacle in a dynamic way -- as a river of ice. However, if the the ELA rises fast enough, ablation burns off enough ice thickness to disconnect the tongue.

Stagnant ice and "dead ice" leave their own characteristic landforms and also specific patterns of sediment deposition. The following figures are from a pair of papers aimed at describing dead-ice melting, let me know if you'd like the cites.

Probably the easiest type of dead ice landform to imagine are ice-cored moraines.

And the easiest example of separation of the glacier snout being retreat over features like cliffs, as in the Fellaria glacier, whose tongue detached in 2006.

It makes, as one WGMS researcher commented, little sense to talk about retreat in length in such a case. The picture is from Flickr and the figure is from a 2012 paper by Diolauti and colleagues, "Evidence of climate change impact upon glaciers’ recession within the Italian Alps."

Powerful shifts in topography assist in producing dramatic examples of glacier breakup and dead ice production, but a group of authors with David Vacco as lead published a paper in 2010 ("Numerical modeling of valley glacier stagnation as a paleoclimatic indicator") saying that in fact, it is possible to model glacier behavior in such a way as to distinguish between glacier breakup due to topography as opposed to breakup as a result of massive downwasting consequent to large magnitude, rapid climate change. If such were the case, they argue that researchers could use evidence derived from the characteristic landforms and sediment deposits left by stagnant glacier melt as a paleoclimate indicator for rapid warming.

If that were true, it would allow us to recognize instances in past climates where deglaciation is marked less by orderly retreat of a glacier via melt at the terminus and more by downwasting across large portions (or all of) the glacier, thinning, stagnation, disintegration, and collapse. Previously stagnant ice melting was a phenomenon mainly discerned in the breakup of continental ice sheets, while valley glaciers were largely considered to undergo dynamic retreat. The late 20th century has provided several case studies of glacier melt via powerful downwasting. As you can see in the Vacco figure, the authors take Mickelson (1971) as a useful example.

Evaluating Vacco and crew's proposition exceeds my training and knowledge, but given the debate in interpreting and synthesizing observations of landforms and sediments in order to determine whether retreat of the ice sheets through (say) Appalachia was marked by stagnant ice deposition, I'm skeptical. However, the Vacco paper is a good pointer to the necessity of having models for deglaciation via rapid loss of thickness.

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Having such a model would be great, because at present men and women hoping to use glaciers as historical- and paleoclimate proxies have to make do with assembling a reconstruction of glacial advance and retreat from (among other things) identifying and dating the classic signs like terminal moraine position, like we saw in the first post on the Matthes map. The previous page also has lots of discussion about methods (including art historical ones!) for reconstucting the position of the glacier front. In short, fluctuations of glacier length is often the easiest (""only"") evidence we can retrieve.

That, of course, tells us about changes in glacier length over time. And that's great.

But getting from length to climate requires several steps, as we saw up above; the climatic setting frames accumulation and ablation, which we translate into volume changes expressed as mass balance. Mass balance in combination with glacier geometry and climate sensitvity in turn are expressed as length changes.

... with the result being that glaciers are a rich source of information for reconstruction of past climate, with the caveat that glacier length is a filtered, smoothed, and delayed indicator. It takes time for large ice bodies to respond to changes in mass balance, and the delay is set by glacier size, shape, and slope, and can range from a mere decade or so to hundreds of years. Seasonal and yearly mass balance are a more direct measure of the relation between glacier and climate.

So ultimately it is possible to use glacier length as a multicentury climate proxy, but at present most methods for doing so have taken a real glacier, such as the Aletsch,

... and reduced it to the most minimal & simple yet robust and useful model. Here you can see a number of different efforts to conceptualize and schematize different types and aspects (size, thickness, shape, slope) of glacial ice. The following figures are from various papers from the 90s forward and are here so we can see how glacier modeling relies on the same ideas about glaciers we learn in school. If you'd like the cites, let me know.

Envisioning glaciers with accumulation areas that act as reservoirs and relating that to fluctuations of the terminus -- a clear mirror for conceptualizing instances such as the Careser in the post above.

The length of time needed for response and nature of glacier recession depends strongly on slope and size. Glaciers need to be treated by class ranging from steep thin mountain glaciers to thick valley glaciers -- and also by climate setting.

Size classes and idealized geometries depicted in plan view:

One of the leading scientists in this area is Johannes Oerlemans, who has been working on models for glacier retreat since the 80s, and the figures above come largely from projects he was involved in. A feature of one of his methods is they emulate the clean-cut imagination of a glacier (as given two posts up) retreating dynamically and as a coherent, flowing mass going from one equilibrium state to another via melt at the terminus. In short many simple representations express long-term changes in glacier area & volume as changes in glacier length, for cases where the retreat of the tongue is a relatively limited fraction of the glacier's overall length. From the post above, we might say they describe the case of small rises in ELA as depicted in the figure from Vacco (2010).

Overall there's a number of different ways to tackle the problem and researchers (Gerard Roe out of U Washington, say) may argue for one or the other more or less complex approach.

The following diagram is taken from a 2014 paper by Peano and crew ("Glacier dynamics in the Western Italian Alps: a minimal model approach") explaining Oerlemans' method as given in his monograph "Minimal glacier models,"

Wherein width is fixed by an appropriate value and ice thickness is assumed to be constant along the entire glacier length, set to a mean ice thickness H. The variable H is then knocked out of the equation by assuming the perfect plasticity of the glacier, such that H can be filled in from length, slope, and pair of derived constants.

... and this reflects Oerlemans' position that for global studies, where detailed information is lacking, fewer inputs is better: his intent is to be able to derive temperature changes from local precipitation, absolute length, and slope.

In 2005 (""Extracting a climate signal from 169 glacier records") and again in 2012 (with first author Paul Leclercq), Oerlemans used an implementation of this model to treat glacier length fluctuations as a proxy to reconstruct climate. The global and Europe-regional reconstructions from the 2012 paper "Global and hemispheric temperature reconstruction from glacier length fluctuations" are given below.

Note the discrepancy between the instrumental record and the proxy for Europe. The lengthy (heh) discussion above offers a possible explanation as to why: its not great at capturing situations of rapid change where volume change occurs mainly via downwasting along a large fraction of the glacier surface. In short, the model doesn't capture conditions where thick ice can't melt "back" fast enough for the mass loss from melting "down" to be reflected in retreat of the terminus. (There's also other reasons why such models might get wonky including debris cover, elevation feedback, and shading effects.) The "long term, filtered, and delayed" aspect of length models here returns with a vengeance.

Vincent and colleagues (2004) emphasize this in their paper "Ice ablation as evidence of climate change in the Alps over the 20th century," and argue that glacier monitoring should utilize mass balance measurement in order to capture the ongoing rapid fluctuations, which are not well captured by terminus retreat.

Meanwhile, the catastrophic disintegration and imminent disappearance of long-term monitered ice bodies such as the Careser means that national and international research groups working in the Alps will need to select new ones with a keen eye towards their potential for longetivity, lest they find themselves monitoring bare rock. Refining glacier models to capture additional aspects of melt behavior is also key to forecasting glacier survival, which Mauri Pelto has argued for the case of the Pacific Northwest.

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While its on my mind from the other thread and because weird glaciers in odd places are neat (click to read about the unwitnessed disappearance of South Africa's glacier)

-- here's an interesting case of revisions that could potentially result from a possible wx station screwup. I don't see that anything has come of this abstract in terms of papers under considerstion or any changes in the Meteo France data for Port-aux-Français or BEST's handling of its station changes, so maybe the identification of error was in error. Maybe someone who has the BEST raws could look at the metadata.

If nothing comes up I'm going to email the authors because I'd love to hear the story and hear what kinds of reinterpretation they think would be needed if they turned out to be right about the temperature time series:




Rwenzori Mountains are pretty much the coolest

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Fascinating posts. Thanks for taking the time to write those up.

Thanks & y/w! I went through and edited / expanded for clarity.

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