Post‐Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10Be cosmic ray exposure dating

Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of ¹⁰Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre‐Little Ice Age (LIA) ice‐marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The ¹⁰Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre‐exposure to secondary cosmic radiation. The moraine was re‐occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three ¹⁰Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented ¹⁰Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.     

The Loch Lomond Readvance on north Arran,Scotland: glacier reconstruction and palaeoclimatic implications

Geomorphological mapping of northern Arran provides evidence for two advances of locally nourished glaciers, the younger being attributable to the Loch Lomond Stade (LLS) of ca. 12.9–11.5 k yr BP, primarily through the mutually exclusive relationship between glacial limits and Lateglacial periglacial features. The age of the earlier advance is unknown. Inferred LLS glacier cover comprised two small icefields and eight small corrie or valley glaciers and totalled 11.1 km². ELAs reconstructed using area–altitude balance ratio methods range from 268 m to 631 m for individual glaciers, with an area‐weighted mean ELA of 371 m. ELAs of individual glaciers are strongly related to snow‐contributing areas. The area‐weighted mean ELA is consistent with a north–south decline in LLS ELAs along the west coast of Great Britain. This decline has an average latitudinal gradient of 70 m 100 km^?1, equivalent to a mean southwards ablation‐season temperature increase of ca. 0.42°C 100 km^?1. Mean June–August temperatures at the regional climatic ELA, estimated from chironomid assemblages in SE Scotland, lay between 5.7 ± 0.1°C and 4.1 ± 0.2°C. Empirical relationships between temperature and precipitation at modern glacier ELAs indicate equivalent mean annual precipitation at the ELA lay between 2002 ± 490 mm and 2615 ± 449 mm. These figures suggest that stadial precipitation on Arran fell within a range between +8% and ?33% of present mean annual precipitation. Copyright © 2006 John Wiley & Sons, Ltd.     

The Younger Dryas glaciation in the southeastern Monadhliath Mountains,Scotland: glacier reconstruction and palaeoclimate implications

Geomorphological mapping of locally nourished glaciers was conducted in four glens in the southeastern Monadhliath Mountains, Scotland. Three glaciers are interpreted to be of Younger Dryas age based on geomorphological similarity to features in other Scottish upland areas known to have been glaciated during the Younger Dryas, and on comparison to adjacent ice‐free areas in the lower glens where landform‐sediment assemblages typically reflect peri/paraglacial readjustment during the stadial. Here we reconstruct Younger Dryas glacier termini based on moraine alignments and associated geomorphological and sedimentological evidence. An adjacent wide plateau area at high altitude may have permitted extensive ice accumulation, but no unequivocal geomorphological signature is evident. To establish upper glacier limits, a series of ice profiles are modelled. The results yield a range of realistic glacier configurations bracketed between two distinct scenarios: a valley glaciation with the glaciers' upper limit on the plateau edge, and a low‐domed icecap centred on the plateau with ice flowing radially into the lower glens. Reconstructed equilibrium‐line altitudes are 795 m a.s.l. for the valley‐glacier scenario and 894 m a.s.l. for the icecap scenario. Calculated mean ablation‐season temperatures at the ELA are 1.2°C and 0.4°C for the valley‐glacier and the icecap scenario, respectively, from which we infer mean annual precipitation rates between 323 and 520 mm a^?1. Palaeoclimate results indicate a stadial climate in central Scotland 65–79% more arid than at present, comparable to that of western Norway for the stadial and to the present‐day Canadian Arctic.     

10Be ages of late Pleistocene deglaciation and Neoglaciation in the north‐central Brooks Range,Arctic Alaska

We present a chronology of late Pleistocene deglaciation and Neoglaciation for two valleys in the north‐central Brooks Range, Alaska, using cosmogenic ¹⁰Be exposure dating. The two valleys show evidence of ice retreat from the northern range front before ～16–15 ka, and into individual cirques by ～14 ka. There is no evidence for a standstill or re‐advance during the Lateglacial period, indicating that a glacier advance during the Younger Dryas, if any, was less extensive than during the Neoglaciation. The maximum glacier expansion during the Neoglacial is delimited by moraines in two cirques separated by about 200 km and dated to 4.6 ± 0.5 and 2.7 ± 0.2 cal ka BP. Both moraine ages agree with previously published lichen‐inferred ages, and confirm that glaciers in the Brooks Range experienced multiple advances of similar magnitude throughout the late Holocene. The similar extent of glaciers during the middle Holocene and the Little Ice Age may imply that the effect of decreasing summer insolation was surpassed by increasing aridity to limit glacier growth as Neoglaciation progressed. Copyright © 2012 John Wiley & Sons, Ltd.     

The Younger Dryas climatic conditions in the Za Mnichem Valley (Polish High Tatra Mountains) based on exposure‐age dating and glacier‐climate modelling

Cosmogenic ³⁶Cl was measured in bedrock and moraine boulders in the Za Mnichem Valley (High Tatra Mountains). The post‐LGM deglaciation of the study area occurred about 15.9 ka ago. The northernmost part of the valley slopes was ice‐free around 15 ka ago. The terminal moraine on the valley threshold was finally stabilized 12.5 ka ago during the Younger Dryas cold event (Greenland Stadial 1). At that time, the Za Mnichem glacier was 1.3 km long and had an area of 0.57 km². The AAR equilibrium line of the glacier was located at 1990 m a.s.l., which corresponds to an ELA depression of ～500 m compared to today. The mean summer temperature was colder by 4°–4.5°C than the present‐day temperature. The mean annual temperature was colder by 6°C than today. Such conditions suggest a decrease of the annual precipitation by ～15–25% compared with the present‐day annual average. These data indicate a probable uniform temperature change across central and western Europe, with the precipitation being the most significant factor affecting the mass balance of mountain glaciers. The spatial distribution of balance data suggests increasing continentality towards the east during the Younger Dryas.     

North Atlantic climate impact on early late‐glacial climate oscillations in the south‐eastern Alps inferred from a multi‐proxy lake sediment record

High‐resolution multi‐proxy analyses of a sediment core section from Lake Jeserzersee (Saissersee) in the piedmont lobe of the Würmian Drau glacier (Carinthia, Austria) reveal pronounced climatic oscillations during the early late glacial (ca. 18.5–16.0k cal a BP). Diatom‐inferred epilimnetic summer water temperatures show a close correspondence with temperature reconstructions from the adjacent Lake Längsee record and, on a hemispheric scale, with fluctuations of ice‐rafted debris in the North Atlantic. This suggests that North Atlantic climate triggered summer climate variability in the Alps during the early late glacial. The expansion of pine (mainly dwarf pine) between ca. 18.5 and 18.1k cal a BP indicates warming during the so‐called ‘Längsee oscillation’. The subsequent stepwise climate deterioration between ca. 18.1 and 17.6k cal a BP culminated in a tripartite cold period between ca. 17.6 and 16.9k cal a BP with diatom‐inferred summer water temperatures 8.5–10 °C below modern values and a shift from wet to dry conditions. This period probably coincides with a major Alpine glacier advance termed the Gschnitz stadial. A warmer interval between ca. 16.9 and 16.4k cal a BP separates this cold phase from a second, shorter and less pronounced cold phase between ca. 16.4 and 16.0k cal a BP, which is thought to correlate with the Clavadel/Senders glacier advance in the Alps. The following temperature increase, coupled with wet (probably snow‐rich) conditions, caused the expansion of birch during the transition period to the late glacial interstadial. Copyright © 2011 John Wiley & Sons, Ltd.     

Holocene evolution of the Triftje- and the Oberseegletscher (Swiss Alps) constrained with <Superscript>10</Superscript>Be exposure and radiocarbon dating

To develop a more precise understanding of Alpine glacier fluctuations during the Holocene, the glacier forefields of the Triftjegletscher and the Oberseegletscher east of Zermatt in the Valais Alps, Switzerland, were investigated. A multidisciplinary approach of detailed geological and geomorphological field mapping combined with ¹⁰Be exposure and radiocarbon dating was applied. A total of twelve samples of boulders and bedrock were taken from both Little Ice Age (LIA) landforms, as documented by the Dufour map published in 1862, and from landforms outside of the LIA. The resulting ¹⁰Be ages range between 12590 ± 350 a and 420 ± 170 a. A piece of wood found embedded in the Little Ice Age moraine gave radiocarbon ages that range between 293 cal years BP up to modern (356–63 cal years before 2013). Based on these results, four tentative steps of the Holocene evolution could be distinguished. An early Holocene stage, which documents the decay of the Egesen stadial glaciers when the first parts of the study area became ice free. This was followed by a phase with no evidence of glacier advance. Then in the late Holocene, the glaciers advanced (at least) twice. An advance around 1200 a, as shown by several moraine ages, coincides with the Göschenen II cold phase. A more extensive readvance occurred during the LIA as shown on the historical maps and underpinned by one ¹⁰Be exposure age and the radiocarbon age. This later advance destroyed or overprinted the earlier landforms in most parts of the area.     

Exposure dating and reinterpretation of coarse debris accumulations (‘rock glaciers’) in the Cairngorm Mountains,Scotland

Relict rock glaciers have considerable potential for contributing to palaeoclimatic reconstruction, but this potential is often undermined by lack of dating control and problems of interpretation. Here we reinvestigate and date four proposed ‘rock glaciers’ in the Cairngorm Mountains and show that the morphology of only one of these appears consistent with that of a true rock glacier produced by creep of underlying ice or ice‐rich sediment. All four features comprise rockslide or rock avalanche runout debris, and the possibility that all four represent unmodified runout accumulations cannot be discounted. Surface exposure dating of the four debris accumulations using cosmogenic ¹⁰Be produced uncertainty‐weighted mean ages of 15.4 ± 0.8 ka, 16.2 ± 1.0 ka, 12.1 ± 0.6 ka and 12.7 ± 0.8 ka. All four ages imply emplacement under cold stadial conditions, two prior to the Windermere Interstade of ca. 14.5–12.9 cal. ka BP and two during the Loch Lomond Stade of ca. 12.9–11.5 cal. ka BP. The above ages indicate that paraglacial rock‐slope failure on granite rockwalls occurred within a few millennia after deglaciation. The mean exposure ages obtained for runout debris at two sites – Strath Nethy (16.2 ± 1.0 ka) and Lairig Ghru (15.4 ± 0.8 ka) – are consistent with basal radiocarbon ages from Loch Etteridge, 22 km to the southwest (mean = 15.6 ± 0.3 cal. ka BP) and imply widespread deglaciation of the Cairngorms and adjacent valleys before 15 ka and possibly 16 ka. Copyright © 2008 John Wiley & Sons, Ltd.     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

‘Little ice age’ variations of outlet glaciers from the jostedalsbreen ice-cap,Southern Norway: A regional lichenometric-dating study of ice-marginal moraine sequences and their climatic significance

Complex moraine-ridge sequences in front of seven outlet glaciers of the Jostedalsbreen ice-cap (Austerdalsbreen, Bergsetbreen, Fåbergstølsbreen, Lodalsbreen, Stegaholbreen, Tuftebreen, Bødalsbreen) are dated using families of lichenometric dating curves established previously at an eighth outlet (Nigardsbreen). Applicability of the Nigardsbreen curves at the regional level is tested using independent historical evidence: moraines deposited during the present century are dated to an accuracy of ± 9.4 yr (16.0%), and most of them are dated to an accuracy of ± 5.5 yr (9.4%). Results from the moraine sequences are combined to form a composite ‘Jostedalsbreen’ record. Median predicted dates for moraine ridges cluster around AD 1939 ± 2 yr, 1929 ± 3, 1908 ± 3, 1886 ± 5, 1875 ± 2, 1867 ± 4, 1855 ± 3, 1842 ± 5, 1822 ± 5, 1807 ± 4 and 1785 ± 5. At least four glaciers reached their ‘Little ice age’ maxima prior to AD 1780, two (Nigardsbreen and Bødalsbreen) at ca. 1750, one (Fåbergstølsbreen) at ca. 1705. Stegaholbreen attained its maximum ca. 1863. Since the ‘Little ice age’ maximum, and despite large differences in glacier size, frontal variations of the various outlets have exhibited a high degree of synchroneity, which suggests that the moraine sequences contain a sensitive record of high-frequency climatic variations over the last ca. 250 yr. During the early twentieth century, measured readvances of the order of 5–150 m over 1–10 yr led to moraine formation. Dendroclimatic evidence indicates that since the late eighteenth century, moraine ridges formed about 5 yr after summer temperature minima and correlate with runs of cool summers (temperature depression of 0.5–1.0°C below the AD 1700–1950 average). Almost simultaneous glacier advances appear to have been caused by reduced ablation. This near-immediate response to climatic variation, by glacier tongues that descend to relative low altitudes, is superimposed upon the longer-term dynamic response of the ice cap to climate.     

Late Holocene great earthquakes and relative sea‐level change at Kenai,southern Alaska

Kenai, located on the west coast of the Kenai Peninsula, Alaska, subsided during the great earthquake of AD 1964. Regional land subsidence is recorded within the estuarine stratigraphy as peat overlain by tidal silt and clay. Reconstructions using quantitative diatom transfer functions estimate co‐seismic subsidence (relative sea‐level rise) between 0.28±0.28 m and 0.70±0.28 m followed by rapid post‐seismic recovery. Stratigraphy records an earlier co‐seismic event as a second peat‐silt couplet, dated to ～1500–1400 cal. yr BP with 1.14±0.28 m subsidence. Two decimetre‐scale relative sea‐level rises are more likely the result of glacio‐isostatic responses to late Holocene and Little Ice Age glacier expansions rather than to co‐seismic subsidence during great earthquakes. Comparison with other sites around Cook Inlet, at Girdwood and Ocean View, helps in constructing regional patterns of land‐level change associated with three great earthquakes, AD 1964, ～950–850 cal. yr BP and ～1500–1400 cal. yr BP. Each earthquake has a different spatial pattern of co‐seismic subsidence which indicates that assessment of seismic hazard in southern Alaska requires an understanding of multiple great earthquakes, not only the most recent. All three earthquakes show a pre‐seismic phase of gradual land subsidence that marked the end of relative land uplift caused by inter‐seismic strain accumulation. Copyright © 2005 John Wiley & Sons, Ltd.     

Late Pleistocene Glacial Events in the Central Apennines, Italy

The study of glacial evidence in the Gran Sasso Massif of the Central Apennines, Italy, has allowed the last maximum advance and the subsequent stadial phases to be dated and the mean annual temperature and quantity of precipitation in the form of snow to be assessed for a number of periods. The glaciers probably reached their maximum extension (Campo Imperatore Stade) ca. 22,600¹⁴C yr B.P. and started to retreat ca. 21,000 yr B.P., leaving behind three recessional moraines. After a first interstade (Fornaca Interstade), the Fontari Stade appears to have taken place shortly after 16,000 yr ago. Ca. 15,000 yr ago the glacier started retreating, leaving behind four more recessional moraines. An interstade (Venacquaro Interstade) preceded the Mount Aquila Stade, datable at ca. 11,000 yr B.P. A strong correlation is evident between the glacial phases on land and the isotopic variations in cores from the Tyrrhenian Sea.     

Glacier fluctuations in the western Alps during the Neoglacial,as indicated by the Miage morainic amphitheatre (Mont Blanc massif,Italy)

Holocene glacier variations pre‐dating the Little Ice Age are poorly known in the western Alps. Studied for two centuries, the Miage morainic amphitheatre (MMA) is composed of three subconcentric sets of c. 25 moraines. Because of its location and of a dominant mode of morainic accretion, the MMA is a well‐preserved marker of the glacier dynamics during the Neoglacial. Radiocarbon dates were obtained by digging and coring in inter‐ morainic depressions of the MMA and through a deep core drilling in a dammed‐lake infill (Combal); complementary data for the inner MMA were obtained by lichenometry and dendrochronology. Radiocarbon chronology shows that (i) the MMA not only pre‐dates the Little Ice Age (LIA), but was built at least since 5029–4648 cal. yr BP (beginning of the Neoglacial); (ii) outer sets of moraines pre‐date 2748–2362 cal. yr BP; (iii) the MMA dammed the Lake Combal from 4.8 to 1.5 cal. kyr BP, while lakes/ponds formed inside the moraines (e.g. from 2147–1928 to 1506–1295 cal. yr BP). The ‘Neoglacial model’ proposed here considers that the MMA formed during the whole Neoglacial by a succession of glacier advances at 4.8–4.6 cal. ky BP (early Neoglacial), around 2.5 cal. ky BP (end of Göschener I), at AD 600–900 (end of Göschener II) and during the LIA, separated by raising phases of the right‐lateral moraine by active dumping because of the Miage debris cover.     

Surface exposure dating of the Great Aletsch Glacier Egesen moraine system,western Swiss Alps,using the cosmogenic nuclide 10Be

Egesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide ¹⁰Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The ¹⁰Be dates range from 10 460±1100 to 9040±1020 yr ago. Three ¹⁰Be dates between 9630±810 and 9040±1020 yr ago are based upon samples from the surfaces of granite boulders. Two ¹⁰Be dates, 10 460±1100 and 9910±970 yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young ¹⁰Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640±430 yr (including the weighted mean of two ¹⁰Be dates of the quartz vein), as a minimum age of deposition of the moraine. All ¹⁰Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog‐bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The ¹⁰Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to ¹⁰Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with ¹⁰Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright © 2004 John Wiley & Sons, Ltd.     

Palaeoclimatic and regional implications of Older Dryas and Younger Dryas local glacier activity in the low-Arctic valley Finnkongdalen,Andøya,northern Norway

Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS ¹⁴C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances.     

Late Quaternary glacial history of Khentey Mountains,Central Mongolia

Mongolian glaciers have been the subject of relatively little research, resulting in less geochronological constraint than other parts of Central Asia. The Khentey Mountains (latitude 47–51°N, longitude 105–112°E) are a typical landlocked mountain range exhibiting clear geomorphic evidence of late Quaternary glaciation. Yet, compared to western parts of Mongolia such as the Mongolian Altay, Gobi Altay, Khangay, and Khovsgol, glacial history of the Khentey Mountains is poorly understood. To address this, and permit comparison of the Khentey glacier–climate record with other alpine regions in Mongolia, we performed geomorphological mapping and cosmogenic ¹⁰Be surface‐exposure dating in two glaciated regions of the Khentey Mountains: Yestii and Khagiin Khar. Specifically, we measured ¹⁰Be in 34 samples collected from five moraine sequences, which, together with morphostratigraphy, correspond to four main glacial stages: (i) The M_y1 terminal moraine sequence for Yestii (21.0±4.9 ka) and the M_k1 moraine for Khagiin Khar (19.6±2.6 ka), both of which represent the Last Glacial Maximum; (ii) the Lateglacial M_k2 moraine, dated to 16.0±3.5 ka; (iii) the M_k3 moraine, dated to either 17.6±7.0 ka (Lateglacial) or 12.1±1.1 ka (Younger Dryas); and (iv) the currently undated M_k4 moraine (~2200 m a.s.l.), to which we assign a Holocene age. Our results suggest that the timing of maximum glacier extent in Mongolia was regionally variable. In the Khentey Mountains, maximum glaciation occurred during Marine Isotope Stage (MIS) 2, whereas the maximum occurred during MIS 3 in Khangay and Khovsgol and during MIS 4 in the Altay. The MIS 2 glacial maximum in the Khentey Mountains coincided with the global sea level minimum during the Last Glacial Maximum, and was followed by at least three glacial re‐advances during the Lateglacial to possibly the Holocene.     

Holocene climatic variations—Their pattern and possible cause

In the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C¹⁴-dated fluctuations of 14 glacier termini show two major intervals of Holocene glacier expansion, the older dating from 3300-2400 calendar yr BP and the younger corresponding to the Little Ice Age of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250-1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030-3300, 2400-1250, and 1050-460 calendar yr BP, and from A.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a third major interval of glacier advances about 5800-4900 calendar yrs BP; this interval generally was less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains in Swedish Lapland reveals again that the Holocene was punctuated by repeated intervals of glacier expansion that correspond to those found in the St. Elias Mountains and elsewhere. The two youngest intervals, which occurred during the Little Ice Age and again about 2300–3000 calendar yrs BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; those of the Little Ice Age culminated about A.D. 1500–1640, 1710, 1780, 1850, 1890, and 1916. In the mountains of Swedish Lapland, Holocene mean summer temperature rarely, if ever, was lower than 1°C below the 1931–1960 summer mean and varied by less than 3.5°C over the last two broad intervals of Holocene glacial expansion and contraction.Viewed as a whole, therefore, the Holocene experienced alternating intervals of glacier expansion and contraction that probably were superimposed on the broad climatic trends recognized in pollen profiles and deep-sea cores. Expansion intervals lasted up to 900 yr and contraction intervals up to 1750 yr. Dates of glacial maxima indicate that the major Holocene intervals of expansion peaked at about 200–330, 2800, and 5300 calendar yr BP, suggesting a recurrence of major glacier activity about each 2500 yr. If projected further into the past, this Holocene pattern predicts that alternating glacier expansion-contraction intervals should have been superimposed on the Late-Wisconsin glaciation, with glacier readvances peaking about 7800, 10,300, 12,800, and 15,300 calendar yr BP. These major readvances should have been separated by intervals of general recession, some of which might have been punctuated by short-lived advances. Furthermore, the time scales of Holocene events and their Late-Wisconsin analogues should be comparable. Considering possible errors in C¹⁴ dating, this extended Holocene scheme agrees reasonably well with the chronology and magnitude of such Late-Wisconsin events as the Cochrane-Cockburn readvance (8000–8200 C¹⁴ yr BP), the Pre-Boreal interstadial, the Fennoscandian readvances during the Younger Dryas stadial (10,850-10,050 varve yr BP), the Alleröd interstadial (11,800-10,900 C¹⁴ yr BP), the Port Huron readvance (12,700–13,000 C¹⁴ yr BP), the Cary/Port Huron interstadial (centered about 13,300 C¹⁴ yr BP), and the Cary stadial (14,000–15,000 C¹⁴ yr BP). Moreover, comparison of presumed analogues such as the Little Ice Age and the Younger Dryas, or the Alleröd and the Roman Empire-Middle Ages warm interval, show marked similarities. These results suggest that a recurring pattern of minor climatic variations, with a dominant overprint of cold intervals peaking about each 2500 yr, was superimposed on long-term Holocene and Late-Wisconsin climatic trends. Should this pattern continue to repeat itself, the Little Ice Age will be succeeded within the next few centuries by a long interval of milder climates similar to those of the Roman Empire and Middle Ages.Short-term atmospheric C¹⁴ variations measured from tree rings correlate closely with Holocene glacier and tree-line fluctuations during the last 7000 yr. Such a correspondence, firstly, suggests that the record of short-term C¹⁴ variations may be an empirical indicator of paleoclimates and, secondly, points to a possible cause of Holocene climatic variations. The most prominent explanation of short-term C¹⁴ variations involves modulation of the galactic cosmic-ray flux by varying solar corpuscular activity. If this explanation proves valid and if the solar constant can be shown to vary with corpuscular output, it would suggest that Holocene glacier and climatic fluctuations, because of their close correlation with short-term C¹⁴ variations, were caused by varying solar activity. By extension, this would imply a similar cause for Late-Wisconsin climatic fluctuations such as the Alleröd and Younger Dryas.     

Chronology of glaciation and deglaciation during the Loch Lomond (Younger Dryas) Stade in the Scottish Highlands: implications of recalibrated 10Be exposure ages

Considerable uncertainty surrounds the timing of glacier advance and retreat during the Younger Dryas or Loch Lomond Stade (LLS) in the Scottish Highlands. Some studies favour ice advance until near the end of the stade (c. 11.7 ka), whereas others support the culmination of glacier advance in mid‐stade (c. 12.6–12.4 ka). Most published ¹⁰ Be exposure ages reported for boulders on moraines or deglacial sites post‐date the end of the LLS, and thus appear to favour the former view, but recalibration of 33 ¹⁰ Be ages using a locally derived ¹⁰ Be production rate and assuming rock surface erosion rates of zero to 1 mm ka^?1 produces exposure ages 130–980 years older than those originally reported. The recalibrated ages are filtered to exclude anomalous data, and then employed to generate aggregate probability density distributions for the timing of moraine deposition and deglaciation. The results suggest that the most probable age for the timing of the deposition of the sampled outermost moraines lies in the interval 12.4–12.1 ka or earlier. Deglacial ages obtained for sites inside Loch Lomond Stadial glacier limits imply that glaciers at some or all of the sampled sites were retreating prior to 12.1 ka. Use of aggregated data does not exclude the possibility of asynchronous glacier behaviour at different sites, but confirms that some glaciers reached their maximum limits and began to retreat several centuries before the rapid warming that terminated the LLS at 11.7–11.6 ka, consistent with the retrodictions of recent numerical modelling experiments and with geomorphological evidence for gradual oscillatory ice‐margin retreat under stadial conditions.     

Lateglacial and early Holocene dynamics of adjacent valley glaciers in the Western Swiss Alps

The Alps play a pivotal role for glacier and climate reconstructions within Europe. Detailed glacial chronologies provide important insights into mechanisms of glaciation and climate change. We present 26 ¹⁰Be exposure dates of glacially transported boulders situated on moraines and ice‐moulded bedrock samples at the Belalp cirque and the Great Aletsch valley, Switzerland. Weighted mean ages of ～10.9, 11.1, 11.0 and 9.6 ka for the Belalp, on up to six individual moraine ridges, constrain these moraines to the Egesen, Kartell and Schams stadials during Lateglacial to early Holocene times. The weighted mean age of ～12.5 ka for the right‐lateral moraine of the Great Aletsch correlates with the Egesen stadial related to the Younger Dryas cooling. These data indicate that during the early Holocene between ～11.7 and ～9.2 ka, glaciers in the Swiss Alps seem to have been significantly affected by cold climatic conditions initiated during the Younger Dryas and the Preboreal Oscillation. These conditions resulted in glacier margin oscillations relating to climatic fluctuations during the second phase of the Younger Dryas – and continuing into Boreal times – as supported by correlation of the innermost moraine of the Belalp Cirque to the Schams (early) Holocene stage. Copyright © 2011 John Wiley & Sons, Ltd.     

Landslide deposits as stratigraphical markers for a sequence‐based glacial stratigraphy: a case study of a Younger Dryas system in the Eastern Alps

Detailed ¹⁰Be and ¹⁴C dating and supporting pollen analysis of Alpine Lateglacial glacial and landslide deposits in the Hohen Tauern Mountains (Austria) constrain a sequence‐based stratigraphy comprising a major landslide (13.0±1.1 ka) overlain by till and termino‐lateral moraines of an advancing (12.6±1.0 ka) and retreating (11.3±0.8 ka) glacier in turn overlain by a minor landslide (10.8±1.1 ka). These results define glacier activity during the Younger Dryas age Egesen stadial bracketed by landslide activities during the Bølling‐Allerød interstadial and the Preboreal. In contrast to recent studies on Holocene glaciation in the Alps, no traces of any Holocene glacier advance bigger than during the Little Ice Age are documented. Furthermore, this study demonstrates the advantages of using an allostratigraphical approach based on unconformity‐bounded sedimentary units as a tool for glacial stratigraphy in formerly glaciated mountain regions, rather than a stratigraphy based on either isolated morphological features or lithostratigraphical characteristics.