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The recently observed recession of glaciers on King George Island is associated with decades of climate warming in the Antarctic Peninsula region. However, with only 60 years of glaciological observations in the study area ages of the oldest moraines are still uncertain. The goal of the study was to estimate ages of lichen colonization on the oldest moraines of the Ecology and White Eagle Glaciers on King George Island and on the Principal Cone of Penguin Island volcano. The first lichenometric studies on these islands from the late 1970s used rates that had about four to five times slower Rhizocarpon growth rates. We re-examined the sites and measured 996 thalli diameters to establish the surface ages. To estimate the age we used (1) long-term Rhizocarpon lichen group growth rates established by authors using data from a previous lichenometric study on King George Island, and (2) previous data of lichen growth rates from other sub-Antarctic islands. Our results suggest growth rates between 0.5 and 0.8 mm yr–1. According to these rates the ages of the oldest moraine ridges are of the Little Ice Age and were colonized at the beginning of the twentieth century. The mid-twentieth century age of lichen colonization on the historically active Penguin Island volcano might support the date of the last eruption reported by whalers in the end of the nineteenth and the beginning of the twentieth century.

On 12 September AD 1717, a rock volume larger than 10 million m3 collapsed onto the Triolet Glacier, mobilized a mass composed of ice and sediment and travelled more than 7 km downvalley in the upper Ferret Valley, Mont Blanc Massif (Italy). This rock avalanche destroyed two small settlements, causing seven casualties and loss of livestock. No detailed maps were made at the time. Later investigators attributed accumulations of granitic boulders and irregular ridges on the upper valley floor to either glacial deposition, or the AD 1717 rock avalanche, or a complex mixture of glacial deposition, earlier rock avalanche and AD 1717 rock avalanche origin. In this study, we present cosmogenic 10Be exposure ages from nine boulders in the extensive chaotic boulder deposit with irregular ridges, two from Holocene glacier-free areas, and one from a Little Ice Age moraine. Exposure ages between 330 ± 23 and 483 ± 123 a from eight of nine boulders from the chaotic deposit indicate that at least seven were deposited by the AD 1717 rock avalanche. The other three boulders yielded 10Be exposure ages of 10 900 ± 400, 9700 ± 400 and 244 ± 97 a, respectively. Our results are in good agreement with the existing chronology from dendrochronology and lichenometry, and radiocarbon analysis of wood samples, but not with older 14C ages from a peat bog in the upper part of the valley. Based on the new age control, the rock avalanche deposits cover the whole bottom of the upper Ferret valley. Copyright © 2012 John Wiley & Sons, Ltd.

Directly measured growth rates of two lichens (Pseudephebe minuscula and Rhizocarpon sections Rhizocarpon and Superficiale) from Svalbard made over a two-decade interval (1984–2007) are presented. Growth rates were determined by measuring the change in area of the lichen thalli from digital images and converting area to diameter. Pseudephebe diameter growth rates ranged from 0.2 to 1.5 mm yr−1 and Rhizocarpon grew 0.05 to 0.30 mm yr−1. Growth rates of both are a function of thalli size—growth rates increase with increasing thallus size up to 70 mm diameter for Pseudephebe and 30 mm diameter for Rhizocarpon. While these directly measured growth rate results are consistent with other recent directly measured lichen growth studies, they are not consistent with indirectly determined age-size curves that show a negative correlation between size and growth rate (i.e., rapid “great growth” followed by slower “linear growth”). We explore several reasons to explain the apparent discrepancy between directl...

Estimates of lichen growth rates based on the measurements of several thalli at any site do not exist for continental Antarctica. However, the very limited existing data suggest that lichen growth rate may be a good indicator of climate change in Antarctica. We present measurements made on thalli of the lichen Buellia frigida Darb. growing in the Dry Valleys, Southern Victoria Land, continental Antarctica, which appear to have some of the slowest radial growth rates yet measured. Photographs of thalli at three different sites were analysed for growth over a 25-year period using nano-GIS techniques. At one site, Mt. Falconer Summit, the lichens had a mean growth rate of 0.0052 mm year−1 with one individual as low as 0.0036 mm year−1. Thalli at the other two sites had significantly higher mean growth rates, 0.0136 mm year−1 at Mt. Falconer Ridge and 0.0118 mm year−1 at Rhone Bench. Assuming a constant growth rate, thalli at Mt. Falconer Summit had a mean age of 5,367 years, whilst the thalli at the other two sites were much younger, 840–1,026 years. We suggest that the different ages represent the appearance of new substrate for colonisation following climate changes in the Dry Valleys that altered the amount and duration of snow. The results confirm that lichen growth rate differs by almost two orders of magnitude over a latitudinal range of 15 degrees from south to north across Antarctica.

The crustose lichen Rhizocarpon geographicum (L.) DC. comprises yellow-green lichenized areolae which develop and grow on the surface of a non-lichenized fungal hypothallus, the latter extending beyond the edge of the areolae to form a marginal ring. The hypothallus advances very slowly and the considerable longevity of R. geographicum, especially in Arctic and Alpine environments, has been exploited by geologists in dating the exposure age of rock surfaces (lichenometry). This review explores various aspects of the biology of R. geographicum including: (1) structure and symbionts, (2) lichenization, (3) development of areolae, (4) radial growth rates (RaGR), (5) growth physiology, (6) changes in RaGR with thallus size (growth ratesize curve), (7) maturity and senescence, and (8) aspects of ecology. Lichenization occurs when fungal hyphae become associated with a compatible species of the alga Trebouxia, commonly found free-living on the substratum. Similarly, 'primary' areolae develop from free-living algal cells trapped by the advancing hypothallus. The shape of the growth rate-size curve of R. geographicum is controversial but may exhibit a phase of decreasing growth in larger thalli. Low rates of translocation of carbohydrate to the hypothallus together with allocation for stress resistance results in very slow RaGR, a low demand for nutrients, hence, the ability of R. geographicum to colonize more extreme environments. Several aspects of the biology of R. geographicum have implications for lichenometry including early development, mortality rates, the shape of the growth-rate size curve, and competition. © The Author(s) 2012.

Matthews, J.A. and Trenbirth, H.E., 2011. Growth rate of a very large crustose lichen (Rhizocarpon subgenus) and its implications for lichenometry. Geografiska Annaler, Series A: Physical Geography...

Lichenometric measurements using Rhizocarpon ssp. were carried out on 20 talus slopes in the cirques of the Finstertal valley (Austria) at an elevation of 2300–3000 m a.s.l. The aim was to assess a...

In the context of reconstruction of Holocene glacier chronologies, there has been a clear tendency during the past few decades towards imprecise use of the term ‘high resolution’. Furthermore, it seems to be increasingly assumed that recently developed terrestrial cosmogenic nuclide dating (TCND) is replacing earlier dating methods. Although recent glaciological knowledge clearly reveals the futility of oversimplified global and inter-hemispheric correlation on the basis of few ‘key’ sites, such comparisons are widely attempted. Stimulated by the example of a recently published article relating to the Southern Alps of New Zealand (Schaefer et al., 2009, Science 324: 622—625) we highlight some related potential problems with the interpretation of Holocene glacier chronologies. In particular, we consider (1) that the term ‘high resolution’ should be applied only to decadal-scale resolution or better and, therefore, not to TCND-based chronologies; (2) that discontinuous moraine chronologies should not be termed high resolution and that their potential geomorphological limitations should be acknowledged; and (3) that TCND-based moraine chronologies should not automatically replace evidence available from other dating techniques but that they should be regarded as complementary and an opportunity for mutual evaluation. Owing to local and regional patterns in glacier response to climate, it is concluded (4) that intra-hemispheric synchroneity in high-resolution Holocene glacier variations is still unproven, and hence (5) that inter-hemispheric comparison is arguably premature, if not impossible. Finally, it is suggested (6) that the first priority for research in this field should be to establish the spatial patterns in glacier behaviour evident at various scales in Holocene records.

Climatic interpretations of recent glacier fluctuations rely on ice-extent chronologies developed from lichenometric ages of Holocene landforms. However, lichenometry requires time- and resource-consuming field surveys, which limit our understanding of glacier chronologies, especially in remote locations. This study presents a rapid, coarse, a priori approach to predicting new field sites where lichenometry can be applied. Geologic, geographic, climatic, and landcover data were used in spatial and supervised classification analyses to identify areas in the Cascade Range of Washington and northern Oregon with similar environmental conditions to those where lichenometric dating techniques had previously been applied. These results focus the attention of researchers to only 1100 km2, or 3%, of the broader Cascade Range study area. Though this study concentrates on the utility of lichenometry for dating recent glacier activity in the Cascade Range, the screening method presented is easily translatable to a va...

This study aims to characterize the morphology and contemporary floodplain deposit dynamics within a braided sandur system in upper Erdalen, a steep U-shaped valley in western Norway. The braided sandur system is fed by two tributary valleys connected to the Jostedalsbreen Ice Field. Based on field observations, two different sub-systems can be identified within the braided sandur system: fine-grained to sandy flood sediments down-valley, and coarser, gravelly deposits in the upper part. A combination of different methods is applied for studying sediment dynamic processes within the braided sandur system (sedimentological and stratigraphic analyses, 14C dating, dendrochronology and lichenometry). The coarser deposits are interpreted as originating from the Little Ice Age advance in Erdalen. Preliminary results indicate that the floodplain sediments were deposited after the Little Ice Age advance. Different sedimentary facies types are present and different phases of flooding can be identified. Within the entire braided sandur system, multiple sub-systems characterized by different levels of process intensities exist.

This paper emphasizes the importance of studying diffuse rock debris accumulation in the far distal part of colluvial cones with the aim of de- fining the spatial distribution and frequency of ex- treme snow avalanches. These deposits are located at some distance from the slope and have rarely been described in the literature. The field based methods used in this study confirm the snow- avalanche origin of these deposits by (i) character- izing the distribution of the deposits along the col- luvial cones and to their furthest extent, some way from the foot of the slope, and (ii) clearly defining the orientation of the long axis of the furthest and largest boulders as parallel with the main cone axis. A relative age of the deposits is obtained by assess- ing the vegetation cover of the boulder surfaces and by measuring the rock hardness using a Schmidt hammer. The study concludes that there were fre- quent extreme snow avalanches which have oc- curred since the Little Ice Age, and that they have decreased in magnitude during the past decade.

In Alaska, lichenometry continues to be an important technique for dating late Holocene moraines. Research completed during the 1970s through the early 1990s developed lichen dating curves for five...

Glaciers in small mountain cirques on South Georgia respond rapidly and sensitively to changes in South Atlantic climate. The timing and rate of their deglaciation can be used to examine the impact that nineteenth- and twentieth-century climate change has had on the glacial dynamics and terrestrial ecosystems of South Georgia. As part of a reconnaissance study in Prince Olav Harbour (POH), South Georgia, we measured the size of lichens (Rhizocarpon Ram. em Th. Fr. subgenus. Rhizocarpon group) on ice-free moraine ridges around two small mountain cirques. Our aims were twofold: first, to provide age estimates for lichen colonization, and hence, deglaciation of the moraine ridges, and second, to examine the potential of applying lichenometry more widely to provide deglacial age constraints on South Georgia. In the absence of lichen age-size (dating) curves for South Georgia, we use long-term Rhizocarpon lichen growth-rates from recent studies on sub-Antarctic Islands and the western Antarctic Peninsula to calculate likely age estimates. These data suggest ice retreat from the two outermost moraines occurred between the end of the 'Little Ice Age' (post c. 1870) and the early twentieth century on South Georgia. Lichen colonization of the innermost moraines is probably related to glacier retreat during the second half of the twentieth century, which has been linked to a well-defined warming trend since c. 1950. Patterns of possible nineteenth- and twentieth-century glacial retreat identified in POH need to be tested further by establishing species- and site-specific lichen age-size (dating) curves for South Georgia, and by applying lichenometry to other mountain cirques across South Georgia.

This paper presents new lichenometric population data from the Antarctic Peninsula (67°S), and describes a new approach to lichen growth-rate calibration in locations where dated surfaces are extremely rare. We use historical aerial photography and field surveys to identify sites of former perennial snowpatches where lichen populations now exist. As an independent check on lichen mortality by snowkill, and the timing of snow patch disappearance, we use a positive-degree day (PDD) approach based on monthly climate data from Rothera Research Station. We find that maximum growth rates for lichens

Snow avalanche impact landforms (SAILs) are typically elliptical-shaped depressions bounded by an arcuate ridge located at the base of avalanche paths. The geomorphology of these features is controlled by the topography of the avalanche path, the availability of unconsolidated debris in the impact area and the ability of the avalanche impacts to displace the available debris in the direction of avalanche flow. Ground-based snow avalanches move debris by bulldozing, and airborne snow avalanches move sediment by excavation on impact. This paper reports on the geomorphology, and surface age and stability of three SAILs in the southern Canadian Cordillera. Dendrochronology and lichenometry were used to date geomorphic activity at the sites. Evidence of present SAIL stability suggests they result from episodic, high-magnitude avalanche impact events over many hundreds of years. All three landforms share common morphologies: a water-filled bowl-shaped depression distally bounded by an arcuate ridge-oriented transverse to the avalanche path. Despite sharing many attributes, field investigations revealed that the origin of each SAIL was a function of the local variations in snow avalanche path topography and availability of unconsolidated debris in the impact area. The snow avalanche path associated with the Blackhorn site has a gentle gradient, which suggests that this SAIL is a result of ground-based avalanches. The SAIL at Spoon Lake appears to be a consequence of a resistant geologic feature that focuses snow avalanches in the impact area and results in explosive excavation. The morphology of the snow avalanche track at Peyto Lake causes large snow avalanches to become airborne prior to impacting and excavating an impact pool. All three SAILs examined in this paper are historically persistent landforms and these observations support previous findings indicating that SAILs require hundreds of years to develop.

This paper presents a critical review of previous lichenometric and lichen growth studies in southern parts of West and East Greenland. These studies include classic work from around Sondre Stromfj...

The reliability of lichenometric dating is dependent on a good understanding of lichen growth rates. The growth rate of lichens can be determined from direct measurement of growing lichens or indirect methods by measuring lichens growing on surfaces of known age, although there are limitations to both approaches. Radiocarbon (14C) analysis has previously been used in only a handful of studies to determine lichen growth rates of two species from a small area of North America. These studies have produced mixed results; a small amount of carbon turnover appears to occur in one of the species (Caloplaca spp.) previously investigated introducing uncertainty in the growth rate, while much higher carbon cycling occurred in another (Rhizocarpon geographicum), making the 14C approach unsuitable for estimating growth rates in the species most commonly used in lichenometric dating. We investigated the use of bomb-14C analysis to determine the growth rate of a different crustose species (Pertusaria pseudocorallina) common to Northern Europe. 14C-based growth rates were considerably higher than growth rates of morphologically similar species based on direct measurement made at locations nearby and elsewhere in the UK. This observation strongly suggests that a degree of carbon turnover probably occurs in Pertusaria pseudocorallina, and that bomb-14C analysis alone cannot be used to determine lichen age or absolute growth rates in this lichen species.

Lichenometry was used to study fluctuations of six glaciers in the Polar Urals over the last millennium (viz: IGAN, Obrucheva, Anuchina, Shumskogo, Avsiuka and Berga glaciers). In order to estimate the growth rate of Rhizocarpon subgenus Rhizocarpon lichens we used recently deglaciated surfaces as calibration sites. These sites, on glacier forelands, were dated using topographic maps, aerial photographs (from 1953, 1958, 1960, 1968, 1973, 1989), terrestrial photogrammetry, field photographs (from the 1960s to 2005), and satellite images (from 2000 and 2008). We also used pits and quarries abandoned between the 1940s–1980s and a road built in the early 1980s as calibration sites. Optimum diametral growth rates of Rhizocarpon subgenus Rhizocarpon are estimated by the new curve to be c. 0.25 mm/year for the last 100 years, assuming linear growth as deduced from the shape of other curves from northern Scandinavia. Due to the lack of old control points we used a reconstructed mass balance curve (from 1816 to 2008) to indirectly constrain the age of pre-twentieth-century moraines. The following moraine groups were identified near the modern fronts of glaciers: ablation moraines de-glaciated during the last 40 to 60 years; lateral moraines formed in the early twentieth century (largest lichen diameter (DLL) = 20 mm), ice-cored moraines, probably from the 1880s (DLL= 24–26 mm); moraines probably deposited in the middle of the nineteenth century and c. 200 years ago (DLL= 30–33 mm and 44–47 mm, respectively); as well as several more ancient moraines (DLL= 70 mm, 90 mm and 110–153 mm) deposited during glacier advances of almost identical extent. According to our tentative lichenometric-age estimates most moraines were formed during the last 450 years – consistent with upper tree-limit altitude variations previously identified for this region. Glacier fluctuations in the Polar Urals are in agreement with tree-ring based reconstructions of summer temperature spanning the last millennium, and are also in tune with glacier behaviour elsewhere in the Northern Hemisphere.

Many Mediterranean steepland rivers are flanked by extensive alluvial and colluvial deposits, but Late Quaternary histories of channel and hillslope behaviour remain poorly constrained, primarily because of the limited availability of material suitable for dating. Study of a 4.8 km long reach of the Anapodaris Gorge, located in the lower part of an � 500 km 2 catchment in south central Crete, reveals a succession of well preserved, coarse-grained (predominantly cobble to boulder) and fine-grained (predominantly silt to sand) alluvial deposits that locally interfinger with, or are overlain by, coarse colluvial and tributary stream deposits. Detailed ground surveys, geomorphological mapping, sedimentological investigations, and geochronology (optically stimulated luminescence, radiocarbon, and lichenometry) have allowed detailed reconstruction of the timing and pattern of sedimentation and erosion over the mid to late Holocene. Widespread, coarse-grained aggradational episodes at c. 4.86-4.20 and c. 3.40-3.00 ka have been punctuated by incisional episodes and coarse sediment export, resulting in a suite of alluvial terraces. Comparison with other proxy Mediterranean environmental change records, particularly high-resolution marine and lake records, suggests that these aggradational/incisional episodes were primarily climatically driven, reflecting changes in the balance between hillslope/tributary sediment supply and high-energy flood events. By contrast, phases of widespread fine-grained aggradation at c. 1.90 ka, 1.13 to 1.10 ka, 0.85 to 0.70 ka and 0.21 ka provide evidence for decreases in flood competence, possibly coupled with up-catchment historical land use changes. Since the middle of the nineteenth century, several large floods have formed localised boulder berms and splays and have contributed to stripping of the fine-grained deposits from many parts of the gorge. The findings from the Anapodaris Gorge demonstrate the sensitivity of Mediterranean steepland catchments to rapid and/or short-lived Holocene climate change but also highlight the need for higher resolution data on historical and prehistoric land use changes. © 2009 Elsevier B.V. All rights reserved.

We reconstructed a chronology of glaciation spanning from the Late Pleistocene through the late Holocene for Fish Lake valley in the north-eastern Alaska Range using 10 Be surface exposure dating and lichenometry. After it attained its maximum late Wisconsin extent, the Fish Lake valley glacier began to retreat ca. 16.5 ka, and then experienced a readvance or standstill at 11.6 � 0.3 ka. Evidence of the earliest Holocene glacial activity in the valley is a moraine immediately in front of Little Ice Age (LIA) moraines and is dated to 3.3-3.0 ka. A subsequent advance culminated at ca. AD 610-900 and several LIA moraine crests date to AD 1290, 1640, 1860 and 1910. Our results indicate that 10 Be dating from high-elevation sites can be used to help constrain late Holocene glacial histories in Alaska, even when other dating techniques are unavailable. Close agreement between 10 Be and lichenometric ages reveal that 10 Be ages on late Holocene moraines may

This study represents the first attempt to develop and apply lichenometric dating curves of Rhizocarpon subgenus Rhizocarpon for dating glacier fluctuations in the Patagonian Andes. Six glaciers were studied along the Patagonian Andes. Surfaces of known ages (historical evidences and tree-ring analyses) were used as control sites to develop indirect lichenometric dating curves. Dating curves developed for the studied glaciers show the same general logarithmic form, indicating that growth rate of subgenus Rhizocarpon decreases over time. The strong west–east precipitation gradient across the Andean Cordillera introduces statistically significant differences in the growth curves, with faster growth rates in the moist west sites than the drier eastern sites. Latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates. Therefore, we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the Patagonian Andes during the past 450 yrs. Application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree-ring analyses. A first chronosequence for moraine formation in the Torrecillas Glacier (42°S) is presented. Our findings confirm the utility of lichenometry to date deglaciated surfaces in the Patagonian Andes.

We mapped Little Ice Age (LIA) moraines in the Brooks Range to estimate former equilibrium-line altitudes (ELAs), and combined this information with available proxy temperature estimates to infer precipitation trends because little is known about precipitation changes associated with centennial-scale climate variability in the Arctic during the late Holocene. The Brooks Range, northern Alaska (68°N), hosts hundreds of extant glaciers that exhibit geomorphic evidence for multiple fluctuations in ice extent during the past millennium. Our lichenometric age estimates for LIA moraines in the forefields of five cirque glaciers in the Sagavinerktok River valley and Oolah Valley suggest two intervals of LIA moraine formation centered around a.d. 1250 and 1650. The outermost LIA moraine was mapped on aerial photographs for 114 relatively large (1.2 ± 0.5 km) and geographically simple glaciers along a 700-km-long transect following the range crest. At their maximum extent during the LIA, these glaciers we...

Tephrochronology utilises age-equivalent horizons of volcanic ash to correlate across landscapes. In Iceland, the proximity of active volcanoes to glaciers and ice caps enables tephrochronology to contribute to a reliably-dated reconstruction of later Holocene glacier advances. This paper reviews the principles and practice of terrestrial tephrochronology in the Icelandic context, supported by examples from recent research. Key issues which are reviewed include the contrasting responses of large ice caps and small mountain glaciers ; the status of the "Little Ice Age " and in particular the timing of its maximum ; the use of tephrochronology to test the reliability of lichenometry ; and the issue of preservation potential and the representativeness of moraine-based chronologies in Iceland., La téphrochronologie utilise les horizons de cendres volcaniques d ' âge similaire pour corréler des dépôts sur de vastes régions. En Islande, la proximité de volcans actifs avec les glaciers permet l 'utilisation de la téphrochronologie pour une reconstitution fiable des avancées glaciaires durant l ' Holocène . Cet article passe en revue les principes et la pratique de la téphrochronologie terrestre en contexte islandais, en s 'appuyant sur des exemples de recherches récentes. Les principaux thèmes abordés sont la dynamique contrastée des calottes glaciaires et des glaciers de montagne, le Petit Age Glaciaire et la date de son maximum, l 'utilisation de la téphrochronologie pour tester la fiabilité de la lichénométrie, et le potentiel de conservation des formes et la représentativité des chronologies basées sur les moraines pour l 'Islande., Kirkbride Martin P. Datation des moraines holocènes d'Islande par tephrochronologie : un état de l'art. In: Collection EDYTEM. Cahiers de géographie, numéro 8, 2009. Neige et glace de montagne. Reconstitution, dynamique, pratiques. pp. 65-78.

Lichenometry—a method developed by geologists for dating Holocene moraines and other landforms—has many potential applications in archaeology. Maximum-diameter lichenometry can suggest ages for features that were initially lichen-free, such as the moai of Easter Island, and rock surfaces exposed by toolstone quarrying. Size-frequency analysis can provide dates for structures built of lichen-covered rocks, such as game-drive walls and blinds, meat caches, and tent rings. Both methods require local calibration curves, best constructed by measuring lichens on substrata of known exposure age. Most lichenometric studies have involved yellow members of the crustose genus Rhizocarpon, which grow slowly and can live for as long as 10,000 years. Lichenometry has been particularly successful on siliceous rock types in arctic, subarctic, and alpine-tundra environments. The effects of wildfire and of competition from foliose lichens make the technique less well suited for forested terrain. Few data are available for tropical or desert environments or for calcareous substrata. The reliability of a lichenometric date will depend on the quality of the calibration curve, the size of the sample, the nature and postoccupational history of the substratum, and the ability of the archaeologist to recognize potential disturbance factors. An ecological perspective is essential. Known archaeological applications and problems are discussed.

The endolithic lichen Lecidea auriculata is known to enhance rock surface weathering on the Little Ice Age moraines of the glacier Storbreen in Jotunheimen, central southern Norway. This s...

This review summarises lichen work in the temperate Southern Hemisphere. A brief historical overview of austral lichenology is presented from the earliest European voyages of discovery up to the present day. Current knowledge is outlined for Australia, New Zealand, South Africa, southern South America, the Southern Subpolar islands, and Antarctica. Biogeographical patterns, and the importance of lichens in nutrient cycling, habitat restoration, and monitoring of global change, are also discussed from an austral perspective.

Two glaciers at Eyjafjallajökull, south Iceland, provide a record of multiple episodes of glacier advance since the Sub-Atlantic period, ca. 2000 yr ago. A combination of tephrochronology and lichenometry was applied to date ice-marginal moraines, tills and meltwater deposits. Two glacier advances occurred before the 3rd century AD, others in the 9th and 12th centuries bracketing the Medieval Warm Period, and five groups of advances occurred between AD 1700 and 1930, within the Little Ice Age. The advances of Eyjafjallajökull before the Norse settlement (ca. AD 870) were synchronous with other glacier advances identified in Iceland. In contrast, medieval glacier advances between the 9th and 13th centuries are firmly identified for the first time in Iceland. This challenges the view of a prolonged Medieval Warm Period and supports fragmentary historical data that indicate significant medieval episodes of cooler and wetter conditions in Iceland. An extended and more detailed glacier chronology of the mid- and late Little Ice Age is established, which demonstrates that some small outlet glaciers achieved their Little Ice Age maxima around AD 1700. While Little Ice Age advances across Iceland appear to synchronous, the timing of the maximum differs between glacier type and region.

Evidence from lake sediments and glacier forefields from two hydrologically isolated lake basins is used to reconstruct Holocene glacier and climate history at Hallet and Greyling Lakes in the central Chugach Mountains of south-central Alaska. Glacial landform mapping, lichenometry, and equilibrium-line altitude reconstructions, along with changes in sedimentary biogenic-silica content, bulk density, and grain-size distribution indicate a dynamic history of Holocene climate variability. The evidence suggests a warm early Holocene from 10 to 6 ka, followed by the onset of Neoglaciation in the two drainage basins, beginning between 4.5 and 4.0 ka. During the past 2 ka, the glacial landforms and lacustrine sediments from the two valleys record a remarkably similar history of glaciation, with two primary advances, one during the first millennium AD, from ~500 to 800 AD, and the second during the Little Ice Age (LIA) from ~1400 to 1900 AD. During the LIA, the reconstructed equilibrium-line altitude in the region was no more than 83 ± 44 m (n = 21) lower than the modern, which is based on the extent of glaciers during 1978. Differences between the summer temperature inferred from the biogenic-silica content and the evidence for glacial advances and retreats suggest a period of increased winter precipitation from 1300 to 1500 AD, and reduced winter precipitation from 1800 to 1900 AD, likely associated with variability in the strength of the Aleutian Low.

A Schmidt hammer was used in conjunction with lichenometry to examine the relative age of the outermost Neoglacial moraines in front of glaciers in the Jotunheimen mountains of southern Norway. Particular attention was directed at (1) the magnitude of the ‘Little Ice Age’ glacier expansion episode relative to any others of Neoglacial age, and (2) the potential and limitations of the Schmidt hammer in the context of Holocene glacial chronologies. Schmidt hammer R-values were measured at 34 glaciers and the sizes of the lichen Rhizocarpon geographicum agg. at 80 glaciers. Unusually low R-values and large lichens suggest the occurrence of pre- ‘Little lee Age’ Neoglacial moraines at only a small minority (< 10 %) of the sampled glaciers. The traditional model of relatively large southern Norwegian glaciers during the ‘Little Ice Age’ is substantiated and it is tentatively suggested that differences in climate or glacier type may account for a regional difference in the status of the ‘Little Ice Age’ between northern and southern Scandinavia. The incorporation of weathered boulders into ‘Little Ice Age’ moraines by glacier push mechanisms, and the altitudinally-related variation in boulder surface textures, are identified as major sources of potential error in the use of the Schmidt hammer R-values for relative-age determination of Neoglacial surfaces.

Samples of glacial till deposited since the Little Ice Age (LIA) maximum by two glaciers, North Bogbre at Svartisen and Corneliussen-breen at Okstindan, northern Norway, were obtained from transects running from the current glacier snout to the LIA (c. AD 1750) limit. The samples were analysed to determine their sediment magnetic properties, which display considerable variability. Significant trends in some magnetic parameters are evident with distance from the glacier margin and hence length of subaerial exposure. Magnetic susceptibility (X) decreases away from the contemporary snout, perhaps due to the weathering of ferrimagnetic minerals into antiferromagnetic forms, although this trend is generally not statistically significant. Trends in the ratios of soft IRM/hard IRM which are statistically significant support this hypothesis, suggesting that antiferromagnetic minerals are increasing relative to ferrimagnetic minerals towards the LIA maximum. Backfield ratios (IRM -100 mT/SIRM) also display a significant and strong trend towards magnetically harder behaviour with proximity to the LIA maximum. Thus, by employing a chronosequence approach, it may be possible to use sediment magnetics data as a tool for reconstructing glacier retreat in areas where more traditional techniques, such as lichenometry, are not applicable.

This article examines the link between late Holocene fluctuations of Lambatungnajokull, an outlet glacier of the Vatnajokull ice cap in Iceland, and variations in climate. Geomorphological evidence is used to reconstruct the pattern of glacier fluctuations, while lichenometry and tephrostratigraphy are used to date glacial landforms deposited over the past /400 years.Moraines dated using two different lichenometric techniques indicate that the most extensive period of glacier expansion occurred shortly before c. AD 1795, probably during the 1780s. Recession over the last 200 years was punctuated by re-advances in the 1810s, 1850s, 1870s, 1890s and c. 1920, 1930 and 1965. Lambatungnajokull receded more rapidly in the 1930s and 1940s than at any other time during the last 200 years. The rate and style of glacier retreat since 1930 compare well with other similar-sized, non-surging, glaciers in southeast Iceland, suggesting that the terminus fluctuations are climatically driven. Furthermore, the pattern of glacier fluctuations over the 20th century broadly reflects the temperature oscillations recorded at nearby meteorological stations. Much of the climatic variation experienced in southern Iceland, and the glacier fluctuations that result, can be explained by secular changes in the North Atlantic Oscillation (NAO). Advances of Lambatungnajokull generally occur during prolonged periods of negative NAO index. The main implication of this work relates to the exact timing of the Little Ice Age in the Northeast Atlantic. Mounting evidence now suggests that the period between AD 1750 and 1800, rather than the late 19th century, represented the culmination of the Little Ice Age in Iceland.

Evidence of past glacier fluctuations is valuable palaeoenvironmental data, but determining their relationship to climatic change is sometimes complex because of differing glacier sensitivities and patterns of response. In Iceland, a diverse range of glaciation creates changing geographical patterns of response to climatic changes. The outlet glaciers of the Mardalsjokull ice cap in southern Iceland have produced detailed, but differing, records of change. For a key southwestern sector of the ice cap, we specifically searched for evidence equivalent to the c. 4500 BP, c. 3100 BP and c. 1200 BP advances of Solheimajokull reported earlier. A combination of geomorphological mapping and dating by tephrochronology and lichenometry was used to constrain the glacier advances and determine the relative magnitude of Neoglacial glacier episodes. This is a key step towards creating a record of the changes for the entire ice cap. Major glacier advances c. 4500–1000 BP previously identified on the southern margin of Mardalsjokull are shown not to have occurred in this sector, where Neoglacial maxima occur post-1755 AD.

Glaciar León is a temperate, grounded outlet of the eastern North Patagonian Icefield (NPI). It terminates at an active calving margin in Lago Leones, a 10 km long proglacial lake. We take a multidisciplinary approach to its description and use ASTER imagery and clast sedimentology to describe the geomorphology of the glacier and its associated moraines. We date periods of glacier retreat over the last 2500 years using a combination of lichenometric, dendrochronological, cosmogenic and optically stimulated luminescence techniques and show that the glacier receded from a large terminal moraine complex some 2500 years ago and underwent further significant recession from nineteenth-century moraine limits. The moraine dates indicate varying retreat rates, in conjunction with significant downwasting. The bathymetry of Lago Leones is characterized by distinct ridges interpreted as moraine ridges that dissect the lake into several basins, with water depths reaching 360 m. The fluctuations of Glaciar León appear to have been controlled by the interplay between climatic forcing and calving dynamics.

Moraine ridges are commonly used to identify past glacier ice margins and so infer glacier mass balance changes in response to climatic variability. However, differences in the form of past ice mar...

The geomorphologic impact of the Little Ice Age (LIA) was determined on two French Mediterranean rivers, the upper Ardeche and the upper Loire. In order to evaluate the impact of the LIA on the hydrology of these rivers, two historical flood chronicles were made from historical sources. The LIA can be divided in three phases of high activity (1530–1700; 1750–1810; 1840–1910). A geomorphologic study of the two rivers shows that incision is the principle process at work in the 20th century. In order to date the low terraces and bedforms present in both valleys, lichenometry was used. Rhizocarpon geographicum allowed the main features on the bottom of the valley to be dated using two growth curves made for the two studied areas. In the Ardeche, lichenometric dating showed a progressive evacuation of the inherited alluvial stock. The oldest lichens found on the foodplain and the outcrops indicate that incision began between the second half of the 17th century and the end of the 18th century, in the mid Little Ice Age. Incision stopped on the bedrock in the second half of the 19th century. In the Loire, the narrowness of the gorge did not allow sediment to be stored during the first half of the LIA. Very old lichens (> 1000 yr of age) are present on the bedrock close to the bed. However at a number of locations, the valley slightly widens, allowing sediment that was transiting through the gorge to be stored. The geomorphologic features that characterise these basins clearly show a hydrosedimentary behaviour different before and after the beginning of the 20th century.

Lichen diameters and radiocarbon dates from the western and southern margins of the Barnes Ice Cap yield a growth curve similar to that from southeastern Baffin Island. As a consequence, the moraine chronology of the northern and western Barnes Ice Cap needs revision, as does the chronology of the large proglacial lakes that existed north of the present Barnes Ice Cap. The revised chronology indicates that moraines were formed along the western margin of the Barnes Ice Cap during the following intervals: (1) less than 100 years ago; (2) 400–500 B.P.; (3) ca. 750 B.P.; (4) ca. 1000 B.P.; (5) ca. 1600 B.P.; (6) ca. 2100 B.P.; and (7) 2800 to 3100 B.P. As the western margin of the Barnes Ice Cap retreated, punctuated by stillstands and readvances, the northern margin of the Barnes Ice Cap lay athwart a series of westerly draining valleys, and a complex of proglacial lakes were dammed between the ice margin and the height of land. This sequence is traced by means of well-developed shorelines, lacustrine deltas, and spillways; specific lake levels are dated by lichenometry. The Barnes Ice Cap moraine sequence is more complex than other Neoglacial records fringing mountain glaciers in Colorado, Alaska and Lappland. However, the chronology for the western Barnes Ice Cap closely resembles independent moraine chronology of mountain glaciers in Cumberland Peninsula, Baffin Island, and thus indicates that the difference between the Baffin Island climatic record and the general Neoglacial/Holocene climatic record (Denton & Karlen, Quaternary Research 7, 1977) is real. Comparison of specific data from Swedish Lappland and Baffin Island shows substantial agreement. Although Neoglacial records may be globally synchronous, the case for a 2500 year periodicity of glacial fluctuations is not proven: a 300 to 600 year return interval is suggested for the period between 0 and 3000 B.P.

Ice-dammed lake Boverbrevatnet existed for 75–125 years in the ‘Little Ice Age’. After about A.D. 1826, glacier retreat led to a fall in lake level and to exposure of the former shoreline, which includes well-developed platforms cut in metamorphic bedrock. The rock platforms, up to 5.3 m wide and backed by cliffs up to 1.55 m high, are partially covered by large angular boulders which form pavements. Accurate levelling has permitted correlation of platform fragments, overflow cols and related features of the shoreline, such as benches eroded in moraines, ice-push ridges, a perched delta, vegetation trim-lines, lichen limits and a ‘lichen-kill’ zone. The evolution of the lake, the chronology of deglaciation and the period of formation of the rock platforms have been dated by lichenometry, supported by 14C dating, Schmidt hammer ‘R’-values and historical data. The morphology of the rock platforms, together with estimates of their rate of erosion ranging from 1.4 to 7.1 cm/year, indicate the importance of frost shattering (frost riving, frost wedging or macrogelivation) at the lake margin under a periglacial climate, while the permanence of such platforms as landscape features suggests their use in the reconstruction of former periglacial environments. A semi-quantitative model is outlined for the development of rock platforms which emphasises deep penetration of the annual freeze-thaw cycle, the movement of unfrozen lake water towards the freezing plane, and the growth of segregation ice in fissures and cracks at the interface between lake ice and bedrock. Ice-push and ice-pull processes are involved primarily as transporting agents in the formation of boulder pavements and in the removal of debris from the platforms. Analogous processes may occur on polar coasts producing coastal rock platforms.

Lichenometry curves were derived for the glacier forelands of Breidamerkurjokull and Skalafellsjokull using measurements of the collective species, Rhizocarpon geographicum, from independently dated surfaces deglaciated during the period since the late-19th century ice maximum episode in the area. The form of the curves appears to be linear. Several methods of predicting the ages of undated surfaces were compared for specific test examples, including single lichenometry curves, families of curves and multiple curves based on randomly selected largest lichens. The last method provided a useful means of assessing the reproducibility of predicted ages. Where substrate conditions were highly variable, a lichenometry curve based on single largest lichens provided a preferred result.

A regular relationship exists between the growth of lichen species within the Section Rhizocarpon and Rhizocarpon alpicola. This can be quantified and used to adjust lichenometric dates to take into account differences in the growth rates of the two groups. R. alpicola colonises deposits later than Section Rhizocarpon species, although subsequent growth by R. alpicola is rapid. If the two groups arc not separated, important dating errors may arise.

Landslides are common in the Polish part of the Flysch Carpathians. They are controlled mostly by lithology and tectonics of the bedrock and by climate. They are a major factor of slope transformation. Rock cliffs within deep landslides are overgrown with lichen thalli of the Rhizocarpon genus, so these cliffs may be dated using lichenometry. This paper presents the basics of lichenometry as well as its applications in geomorphological research in Poland and worldwide. Also presented are results of lichenometric dating of landslide–rockfall walls in the western part of the Polish Flysch Carpathians. The study helps to identify landslide episodes from historical times. The results obtained indicate that on the slopes studied there coexist several generations of landslide–rockfall forms of various age, including recent and active ones.

A new lichen dating method and new moraine observations enabled us to improve the chronology of glacier advances in the Cordillera Blanca (Peru) during the Little Ice Age (LIA). Our results reveal that an early LIA glacial advance occurred around AD 1330 +/- 29. However, a second major glacial advance at the beginning of the 17th century overlapped the earlier stage for most glaciers. Hence, this second glacial stage, dated from AD 1630 +/- 27, is considered as the LIA maximum glacial advance in the Cordillera Blanca. During the 17th-18th centuries, at least three glacial advances were recorded synchronously for the different glaciers (AD 1670 +/- 24, 1730 +/- 21, and 1760 +/- 19). The moraines corresponding to the two first stages are close to the one in 1630 suggesting a slow recession of about 18% in the total length of the glacier. From the LIA maximum extent to the beginning of the 20th century, the 24 glaciers have retreated a distance of about 1000 in, corresponding to a reduction of 30% in their length. This rate is comparable to that observed during the 20th century. Estimates of palaeo-Equilibrium Line Altitudes show an increase in attitude of about 100 m from the LIA maximum glacial extension at the beginning of the 17th century to the beginning of the 20th century. Because long time series are not available for precipitation and temperature, this glacial retreat is difficult to explain by past climate changes. However, there is a fair correspondence between changes in glacier length and the delta O-18 recorded in the Quelccaya ice core at a century timescale. Our current knowledge of tropical glaciers and isotope variations leads us to suggest that this common tropical signal reflects a change from a wet LIA to the drier conditions of today. Finally, a remarkable synchronicity is observed with glacial variations in Bolivia, suggesting a common regional climatic pattern during the LIA.

Geografisk Tidsskrift, Danish Journal of Geography 108(1):143–151, 2008 Different field methods, which may result in lichen growth curves and lichenometric dating curves, respectively, are outlined and discussed. Emphasis is laid on various factors that need to be taken into consideration in order to avoid errors. The importance of having many control points and minimizing of heterogeneous habitat factors in establishing the sample areas are stressed. It is also important to be aware of some problems regarding the lichen taxa, which are commonly used for lichenometric purposes. A recent example of the application of this particular technique on a glacier foreland at the Mittivakkat Glacier on Ammassalik Island in South East Greenland is discussed.

Lichenometry is a method of dating that has been widely used in glaciated areas for determining the minimum age of exposure of a geomorphic landform during the late Holocene. This paper presents a regional calibration data set of lichen thallus sizes versus rock surface ages for the Huashan area, East China, based on measurements of yellow-green Rhizocarpon lichens on the known-age substrates at eight sites. An empirical relationship between thallus sizes and rock surface ages was established using both the traditional regression and the Bayesian approaches. Using the Bayesian calibration, the minimum age of the Huashan Grottoes was dated from 450 ± 60 to 330 ± 60 years ago, corresponding to the late Ming Dynasty (AD 1477–1632). These dates are generally consistent with those predicted from the regression-based linear growth curve. Our results suggest that applications of this technique can be safely extended to the non-glaciated areas.

Global temperature rise is suggested to be greater and more rapid in polar regions. There has been a clear temperature rise of 0.056 °C y−1 in the Antarctic Peninsula and this has led to changes in higher plant extent and range. In the more extreme environments of the main continent the vegetation is scattered and composed of lichens and mosses. There is interest in the possible effects of global climate change on these communities acting through changes in temperature and precipitation. Lichens have been extensively used to date the substrates on which they are growing using the techniques of lichenometry. The slow growth and longevity of lichens particularly suites them for this use. We present evidence that there appears to be a substantial (two orders of magnitude) cline in lichen growth rate from the warmer, wetter and more productive Peninsula to the cold Dry Valleys at 77°S latitude. The differences in growth rate reflect the precipitation and temperature regimes at the different sites. The large range in growth rates coupled with the simplicity of measuring lichen growth using modern techniques suggests that this could be an excellent tool for the detection of climate change in continental Antarctica.

The dates of recession of eleven outlet glaciers of the Hielo Patagonico Norte (Northern Patagonian Icefield) from their recent maximum positions have been inferred from dendrochronology, lichenometry, radiocarbon dating and historical sources. We have refined the dating for part of the Little Ice Age period in this area placing a glacial advance to between AD 1650 and 1766 with the latter date favoured as conformable with historical records and an uncalibrated radiocarbon determination. Glacier recession from maximal positions began in the early 1860s–1870s. Recession was largely synchronous on the western and eastern sides of the Icefield. This synchronicity suggests that climate forcing over-rides second-order controls on glacier behaviour such as the nature of the terminal environment (e.g. calving/non-calving) or differences in glacier drainage basin area. We argue that this icefield-wide glacier recession represents a response to post-Little Ice Age warming, and provides further evidence for the global extent and near synchronous termination of the Little Ice Age.

The Little Ice Age glacier history in Garibaldi Provincial Park (southern Coast Mountains, British Columbia) was reconstructed using geomorphic mapping, radiocarbon ages on fossil wood in glacier forefields, dendrochronology, and lichenometry. The Little Ice Age began in the 11th century. Glaciers reached their first maximum of the past millennium in the 12th century. They were only slightly more extensive than today in the 13th century, but advanced at least twice in the 14th and 15th centuries to near their maximum Little Ice Age positions. Glaciers probably fluctuated around these advanced positions from the 15th century to the beginning of the 18th century. They achieved their greatest extent between A.D. 1690 and 1720. Moraines were deposited at positions beyond present-day ice limits throughout the 19th and early 20th centuries. Glacier fluctuations appear to be synchronous throughout Garibaldi Park. This chronology agrees well with similar records from other mountain ranges and with reconstructed Northern Hemisphere temperature series, indicating global forcing of glacier fluctuations in the past millennium. It also corresponds with sunspot minima, indicating that solar irradiance plays an important role in late Holocene climate change.

Macklin, Mark, Rumsby, B.T., (2007) 'Changing climate and extreme floods in the British uplands', Transactions of the Institute of British Geographers 32(2) pp.168-186 RAE2008

A small cirque glacier is present in a north-east facing cirque on the mountain of Šljeme (2455 m as.l.) in the Durmitor massif, Montenegro. Sediment ridges in front of this glacier are interpreted as moraines and can be attributed to recent glacier activity over the past 130 years. Lichenometry was applied to determine the relative ages of different moraines using Aspicilia calcarea agg. One set of moraines dates from about 1878 AD, whilst another set of inner moraines dates from about 1904 AD. The most recent moraines appear to have formed within the last 11 years in front of an active glacier margin. Copyright © 2007 John Wiley & Sons, Ltd.

This paper reviews evidence from previous growth-rate studies on lichens of the yellow-green species of Subgenus Rhizocarpon - the family most commonly used in lichenometric dating. New data are presented from Rhizocarpon section Rhizocarpon thalli growing on a moraine in southern Iceland over a period of 4.33yr. Measurements of 38 lichen thalli, between 2001 and 2005, show that diametral growth rate (DGR, mmyr-1) is a function of thallus size. Growth rates increase rapidly in small thalli ( 50 mm diameter). Mean DGR in southern Iceland, between 2001 and 2005, was 0.64 mm yr-1 (SD = 0.24). The resultant growth-rate curve is parabolic and is best described by a third-order polynomial function. The striking similarity between these findings in Iceland and those of Armstrong (1983) in Wales implies that the shape of the growth-rate curve may be characteristic of Rhizocarpon geographicum lichens. The difference between the absolute growth rate in southern Iceland and Wales (ca. 66% faster) is probably a function of climate and micro-environment between the two sites. These findings have implications for previous lichenometric-dating studies, namely, that those studies which assume constant lichen growth rates over many decades are probably unreliable. © British Geological Survey/ Natural Environment Research Council copyright 2006.