Cirque Glaciers Research Articles

Surge fingerprinting of cirque glaciers at the Tröllaskagi peninsula, North Iceland

The geomorphology and sedimentology of the Teigarjökull and Búrfellsjökull, two small surge-type cirque glaciers at the Tröllaskagi peninsula, northern Iceland was explored for improved understanding of their surge imprints. Geomorphological, geological and remote sensing data on sediments and landforms were used for developing a geomorphological model for surge-type cirque glaciers in Iceland. Most surge moraines identified are in the form of uneven small ridges or debris sheets that constitute a boulder-rich hummocky terrain. The size and structures of two moraines in front of Teigarjökull are interpreted as suggesting that the glacier has in the past switched between surge and non-surge behavior. Hummocky surfaces, small medial moraines and crevasse-fill ridges are common, as are landforms suggesting dead-ice melting, such as backslumping, extension cracks and sinkholes. The surface sediments are rich in subangular and angular pebbles, cobbles, and boulders. This distinct geomorphology of the glacier forefields results from ample supply of coarse and angular sediments originating from the steep mountain slopes bordering the glaciers and subsequently carried to the marginal zone via englacial and supraglacial transport.

Cirque glacier reconstruction at the eastern margin of the Alps

Cirque glacier reconstruction at the eastern margin of the Alps

Ice caps in the Balkans: their, extent, age, and palaeoclimatic significance

Ice caps once covered large areas of Montenegro in the Balkans. The largest ice cap covered an area of >1000 km2 and covered large areas of central Montenegro, including the Durmitor, Sinjajevina and Mora?a massifs. A smaller ice cap, yet still covering an area of 165 km2, covered Mount Orjen on the Adriatic coast. More than 30 U-series dates from secondary carbonates cementing moraines across Montenegro indicates that the most extensive glaciation occurred during the Middle Pleistocene, correlating with a major phase of glaciation in Greece to the south during MIS 12 (c. 480-430 ka). Later, less extensive, glaciations are also recorded in the cirques and valleys and correlate with glaciations during MIS 6 (190-130 ka) and MIS 5d-2 (110-11.7 ka). The formation of large ice caps over Montenegro on mountains reaching only 2500 m indicates sustained moisture supply during Pleistocene cold stages ? especially on the lower mountains of the coast such as Mount Orjen. Such sustained precipitation supply during Pleistocene cold stages is likely to have been facilitated by major temperature contrasts between the European landmass and the Mediterranean Sea, which are likely to have sustained lee-side vortices to the south of the Alps, in the Gulf of Genoa and Adriatic Sea, forming weak moisture-bearing depressions which tracked across the eastern Adriatic coastal mountains. Large ice caps on the Dinaric Alps would have blocked the inland penetration of these depressions, resulting in much drier conditions in the Balkan interior, creating favourable conditions for the deposition of thick accumulations of loess. In the Durmitor massif, the highest in Montenegro, valley glaciers were present during the Younger Dryas (12.9-11.7 ka) and confirm the influence of North Atlantic Ocean circulation on Pleistocene climate change in this part of the Mediterranean. In this same massif only one small cirque glacier survives today and exists under conditions strongly controlled by local topoclimatic controls.

10Be-based Chronologies of Cirque Glaciation Across Western North America

10Be-based Chronologies of Cirque Glaciation Across Western North America

Reconstruction of glacier fluctuation (East Siberia, Russia) during the last 160 years based on high-resolution geochemical proxies from proglacial lake bottom sediments of the Baikalsky Ridge

The object of our study is a cirque glacier located in an alpine-type terrain near Mount Chersky in the Baikalsky Ridge, about 18 km to the west of the northern basin of Lake Baikal (Russia). We analysed a sediment record from the pro-glacial Lake Gitara of this glacier by X-ray fluorescent technique with synchrotron radiation (equipment of Multiple Access Centre SSTRC within the framework of State Contract 16.552.11.7044) at 1 mm scan resolution. The depth–age model of the core was constructed by 210Pb and 137Cs activity using the constant rate of supply model. The intensity of the glacier fluctuation for the last 160 years was calculated from the ratio of terrigenous elements supplied into Lake Gitara with meltwater. We defined five (c. 1880, 1905, 1918, 1950 and from 1968 to the present) significant periods of increased glacier flow for the last 160 years. The periods centred on 1905 and 1918 were probably characterised by the advance of the glacier, while its retreat was recorded in c. 1880, 1950 and from 1968 to the present.

Late Pleistocene glaciers in the western Rodna Mountains, Romania

Glacial landforms are commonly found throughout the highest belt (above ∼1700 m a.s.l.) of the Romanian Carpathians. This paper presents glacial geomorphological evidence from the Zănoaga Mare, Zănoaga Iezerului and the western part of Buhăescu valley complex situated on the northern slope of the Rodna Mountains, in the Eastern Carpathians, Romania. GIS-based geomorphological mapping reveals five sets of moraines in glacial phases assigned to the Late Pleistocene. The most extensive glacier was in western Buhăescu valley and had a surface area of 5 km2 and a length of 4.2 km and reached down to an altitude of 1086 m. Several methods were tested to determine the former ELAs of the glaciers. Using size-specific AAR, the average ELA for the oldest phase was 1765 m and rose to 1865, 1960, 2001 and 2025 m. The last and youngest phase was characterised only by cirque glaciers. Comparison with previous studies shows that extents were over-estimated.

Periglacial weathering and headwall erosion in cirque glacier bergschrunds

Glaciers produce cirques by scouring their beds and sapping their headwalls, but evidence to constrain models of these processes has been elusive. We report a suite of environmental measurements from three cirque glacier bergschrunds, including the first temperature series recorded at depth throughout most of an annual cycle. Compared to the ambient air, the bergschrunds were colder in summer and warmer in winter. Freeze-thaw cycles were rare, and relatively stable subfreezing temperatures persisted from November until May. Using a model for rock fracturing driven by ice segregation, we demonstrate that favorable conditions for fracturing occur not only on the headwall above the glacier, but also within the bergschrund, where periglacial weathering and glacial transport can act together to drive cirque headwall retreat. A small (∼3 °C) year-round decrease in temperatures to conditions more typical of the Pleistocene would likely intensify the weathering process. Though so far ignored in all glacial landscape evolution models, the bergschrund likely plays an essential role in the sculpting of alpine landscapes.

Maximum glacial advance and deglaciation of the Pinar Valley (Sierra de Gredos, Central Spain) and its significance in the Mediterranean context

Pinar Valley is located on the north side of Galana Peak (40° 15′ 21″ N; 5° 18′ 00″ W; 2564m a.s.l.), Sierra de Gredos, in the center of the Iberian Peninsula. Surface exposure ages based on the in situ accumulation of 36Cl were obtained from six moraine boulders and from three bedrock outcrops to investigate the timing of both the last local glacial maximum and the deglaciation. The oldest moraines, which probably overrode older glacial deposits, are coeval to the global Last Glacial Maximum. Subsequently the Pinar glacier underwent minor pulsations close to its maximum position, followed by general glacier retreat after ~17–16ka. Small cirque glaciers probably remained during the terminal Pleistocene but they had completely disappeared by 10ka.

The plateau glacier in the Sierra de Béjar (Iberian Central System) during its maximum extent. Reconstruction and chronology

A detailed study of the glacial morphology in the Sierra de Béjar (Iberian Central System) provided a data set of geomorphic indicators to reconstruct the paleoglaciers developed in this mountain area during the last glacial cycle (Late Pleistocene). Applying a physical-based glacier model and using the geomorphic indicators, a three dimensional reconstruction of the ice mass during the maximum extent of the glaciers has been carried out. We used this reconstruction to project hypsometric curves over the former glaciers and to estimate the ELAs (Equilibrium Line Altitudes) of the paleoglaciers for their stage of maximum extent. At this stage the Sierra de Béjar hosted a plateau glacier, considered as a dome-shaped icecap around 57km2 in area. According to our estimations, the maximum thickness of the ice was 211m, the minimum elevation of paleoglaciers 1210m asl, and the regional ELA was at 2010m asl. During later stages, reduction in ice mass due to deglaciation caused the icecap to evolve into an icefield, and finally the main glacier was fragmented in valley and cirque glaciers. The geochronological data obtained with 10Be provides an age of ~27ka for the maximum extent of the glaciers (GM), whereas the global Last Glacial Maximum (LGM) represents a younger stage of the Sierra de Béjar glacier evolution. Finally, the new data obtained in the Sierra de Béjar allow evaluating the influence of some factors such as the continentality and latitudinal location, in the development of glacial processes in these areas of the Iberian Central System.

Response of the Irish Ice Sheet to abrupt climate change during the last deglaciation

We summarize 121 14C and in-situ cosmogenic (10Be and 36Cl) ages that constrain fluctuations of the Irish Ice Sheet (IIS) since the Last Glacial Maximum (LGM) that can be linked to abrupt climate changes in the North Atlantic region. These data provide a robust means to date ice-sheet fluctuations because similar-age events can be identified from widely spaced sites, they are constrained by stratigraphy, and they can be related to large changes in the configuration of a dynamic ice sheet. The following events are recognized. (1) AMS 14C ages and 10Be and 36Cl ages as well as offshore data suggest that the last maximum advance of the IIS occurred between ∼27 and 23 cal ka. (2) Deglaciation began on the western continental shelf and in the Irish Sea Basin at ∼23 cal ka. Dated sites from around Ireland constrain subsequent widespread retreat of ice-sheet margins from the shelf onto Irish coastlines during the Cooley Point Interstadial ≥20 cal ka. AMS 14C ages suggest that the Cooley Point Interstadial continued until ≤18.2 cal ka B.P. During this interstadial, retreat of the ice-sheet margin into the northern Irish Sea Basin indicates that the IIS may have lost up to two-thirds of its mass. (3) Dated sites from northwestern and eastern Ireland indicate that the Cooley Point Interstadial was terminated by ice readvance during the Clogher Head Stadial at ∼18.2 cal ka. (4) The Linns Interstadial was a brief interval (≥17.0–≥16.5 cal ka) of ice recession following the Clogher Head Stadial that is identified from raised marine sediments in eastern and northern Ireland and cosmogenic ages elsewhere in Ireland. (5) The IIS subsequently readvanced during the Killard Point Stadial, reaching its maximum extent ∼16.5 cal ka, indicating that the readvance began sometime earlier. (6) Widespread retreat of the IIS began by ∼15.5 cal ka during the Rough Island Interstadial. (6) Readvance of cirque glaciers in western Ireland occurred during the Younger-Dryas equivalent Nahanagan Stadial.

Palaeoclimatic reconstruction from Lateglacial (Younger Dryas Chronozone) cirque glaciers in Snowdonia, North Wales

The cirques of Snowdonia, North Wales were last occupied by glacier ice during the Younger Dryas Chronozone (YDC), c. 12.9–11.7ka. New mapping presented here indicates 38 small YDC cirque glaciers formed in Snowdonia, covering a total area of 20.74km2. Equilibrium line altitudes (ELAs) for these glaciers, calculated using an area–altitude balance ratio (AABR) approach, ranged from 380 to 837m asl. A northeastwards rise in YDC ELAs across Snowdonia is consistent with southwesterly snow-bearing winds. Regional palaeoclimate reconstructions indicate that the YDC in North Wales was colder and drier than at present. Palaeotemperature and annual temperature range estimates, derived from published palaeoecological datasets, were used to reconstruct values of annual accumulation and ‘winter balance plus summer precipitation’ using a degree-day model (DDM) and non-linear regression function, respectively. The DDM acted as the best-estimate for stadial precipitation and yielded values between 2073 and 2687mma−1 (lapse rate: 0.006°Cm−1) and 1782–2470mma−1 (lapse rate: 0.007°Cm−1). Accounting for the potential input of windblown and avalanched snow onto former glacier surfaces, accumulation values dropped to between 1791 and 2616mma−1 (lapse rate: 0.006°Cm−1) and 1473–2390mma−1 (lapse rate: 0.007°Cm−1). The spatial pattern of stadial accumulation suggests a steep precipitation gradient and provides verification of the northeastwards rise in ELAs. Glaciers nearer the coast of North Wales were most responsive to fluctuations in climate during the YDC, responding to sea-ice enforced continentality during the coldest phases of the stadial and to abrupt warming at the end of the stadial.

The glacial history of the Dinaric Alps, Montenegro

Large areas of Montenegro were glaciated during the Pleistocene. This paper presents evidence from the massifs of central Montenegro, including Durmitor and Sinjajevina, Moračke Planine, Maganik, Prekornica and Vojnik. Glacial deposits have been subdivided on the basis of morphostratigraphy and soil weathering and 31 U-series ages from cemented tills provided a geochronological framework. The largest glaciation occurred before 350 ka when a series of conjoined ice caps over the massifs of central Montenegro covered a total area of nearly 1500 km 2. These formed during MIS 12 and correspond with the largest Skamnellian Stage glaciations in Greece to the south. Later Middle Pleistocene glaciations occurred during the penultimate glacial cycle correlating with the Vlasian Stage in Greece (MIS 6) when ice caps covered an area of 720 km 2 over central Montenegro. There is also geochronological evidence of glacial deposits dating from the interval between MIS 12 and MIS 6, before the interglacial complex of MIS 7. This glaciation appears to have been very similar in extent to that which occurred during MIS 6. The last glacial cycle in central Montenegro was characterised by valley and cirque glaciers covering a total area of 49 km 2. It is very likely that glaciers have been present in the mountains of central Montenegro during every glacial cycle since a small glacier still survives today. The smaller glaciers of the last glacial cycle are likely to have been associated with summer temperatures that were warmer than those of earlier cold stages. The striking contrast in the extent and thickness of ice cover during the cold stages of the Pleistocene has an important bearing on the geomorphological and biological evolution of the Balkans.

Response of a mid-latitude cirque glacier to climate over the last two decades: Mangaehuehu Glacier, Mt Ruapehu

The recent loss of mountain glaciers in response to climate warming has been reported across a range of latitudes globally, but the processes involved are not always straightforward. In southern Pacific mid-latitudes, twentieth-century glacier fluctuations are thought to reflect the strength of westerly atmospheric circulation, which brings increased precipitation, leading to mass gains. We present a study of the response of Mangaehuehu Glacier, a cirque glacier on Mt Ruapehu, to climate over the last two decades. Glacier surface area fluctuated in size over this period, corresponding closely with mean end-of-summer snowlines in the Southern Alps. The key control on glacier extent appears to be ablation season temperature, itself controlled by regional atmospheric circulation, including El Nino-Southern Oscillation, Interdecadal Pacific Oscillation (IPO), and to a lesser extent, Southern Annular Mode (SAM). Copyright © 2011 John Wiley & Sons, Ltd.

Recognition and paleoclimatic implications of late-Holocene glaciation on Mt Taranaki, North Island, New Zealand

Evidence for the timings of inter-hemispheric climate fluctuations during the Holocene is important, with mountain glacier moraine systems routinely used as a proxy for climate. In New Zealand such evidence for glacier expansion during the late Holocene is fragmentary and is limited to glaciers in a narrow zone within the Southern Alps. Here, we present the first evidence for late-Holocene glacier expansion on the North Island of New Zealand in the form of two unconsolidated debris ridges on the south side of the stratovolcano, Mt Taranaki/Mt Egmont, at ~1920 m a.s.l. The two ridges are aligned north–south along the western and eastern sides of a small basin (Rangitoto Flat), which is formed between the main Taranaki cone (to the north), and the parasitic cone of Fanthams Peak (to the south). The approximate age of the ridges is constrained by dated eruptive events and the relationship between ridge locations and the spatial positioning of adjacent volcanic landforms. We propose the ridges formed as two lateral moraines on the margins of a cirque glacier during the final construction phase of Fanthams Peak between 3.3 and 0.5 ka BP, during late-Holocene time. This time interval accords with published cosmogenic 10Be dating of moraine-building episodes in the Southern Alps, indicating the Mt Taranaki moraines are a response to the same regional climatic forcings.

Long‐runout rockslide on glacier at Tsar Mountain, Canadian Rocky Mountains: potential triggers, seismic and glaciological implications

AbstractA rhomboidal shaped rockslide with a length of 2·2 km and an area of 1·35 km2 covers 30% of a small Clemenceau Icefield Group cirque glacier. By means of remote sensing, airborne photography, climate and seismic data analysis, the extent, timing, possible trigger mechanisms, and rockslide effects on the glacier are discussed. An ML 2·0 seismic event on 14 September 2000 represents the rockslide and has a spindle‐shaped waveform and high energy in the low frequencies. Based on a strong signal duration of 56–108 seconds the rockslide had an average runout velocity of 22–45 m s−1. Stress fatigue and a combination of rain and snow followed by rapid melt and night‐time freezing could have co‐triggered the slide. Additional seismic events with epicentres <40 km from the cirque were recorded 26 times since 1985 and range between ML 0·9–3·3, but none were caused by, or triggered, large mass movement.With a rock source volume of 1·6 × 106 m3 and a deposited volume of 2–4 × 106 m3 the sum of bulking and entrainment is between 25% and 150%. Five melt seasons post‐event, levees 20–30 m wide tower 30 m over the surrounding glacier. Rockslide characteristics, and its Fahrböschung of 15° [height/length (H/L) = 0·28], indicate that this rockslide is quite typical for long‐runout rockslides on glaciers. However, the basal friction coefficient was higher than found on other glaciers and could relate to the presence of medial moraines transverse to the flowline and to pre‐slide debris‐cover. The difference between the coefficient of friction in the main flowline (0·11–0·14) and that in a lobe confined between two medial moraines (0·065) suggests that confinement increases mobility by 70–115%. Apart from reduced ablation under the rock debris, effects of the rockslide on the glacier were minimal. Copyright © 2010 John Wiley & Sons, Ltd.

Beringia: Impact on paleoclimates of northeast Asia and North Pacific during Last Pleistocene glaciation

The Beringian land bridge that emerged repeatedly during ice ages was of great importance in the energy and matter redistribution within the “continent – ocean” system and had a pronounced effect on air streams and surface marine currents in the North Pacific region. The paper considers an important and still unsettled paleogeographic problem of the Arctic Northeast of Asia: could Beringia have been covered with an ice sheet at the last glacial maximum? and what was the natural refrigerator impact on regional climate and paleo-oceanography of the Northern Pacific? Based on studies of diatoms and pollen spectra recovered from deposits dated to the last glacial time, Western Beringia was essentially ice-free at that time. This may be attributed to a deficiency of moisture supply from the Pacific due to changes in vectors and intensity of the North Pacific currents. The thick snow cover needed for glacier formation could not accumulate. Western Beringia was dominated by a unique landscape of cold and dry tundra-steppe, its topography being complicated with arcuate ridges – end moraines of alpine and cirque glaciers. The glaciation of the region developed according to the North Yakutia scenario.

Subsurface hydrology of an overdeepened cirque glacier

AbstractTo investigate the subsurface hydrological characteristics of an overdeepened cirque glacier, nine boreholes were drilled to the bed of West Washmawapta Glacier, British Columbia, Canada, in summer 2007. All holes were surveyed with a video camera, and four were subsequently instrumented with a combination of pressure transducers, thermistors and conductivity sensors. Diurnal pressure and temperature records indicate the presence of a hydraulically connected subglacial drainage system towards the northern glacier margin. Hydraulic jacking in the overdeepening, controlled by changing water volume in the marginal zone, potentially impacts basal ice flow and erosion. The presence of a sediment layer underlying the glacier also likely impacts hydrology and ice dynamics. Influx of warm groundwater into the basal system raises subglacial water temperatures above the pressure-melting point (pmp) and induces diurnal water temperature fluctuations of as much as 0.8°C; water temperatures above the pmp could affect basal melt rates and the development of subglacial drainage systems. These observations suggest that the characteristics of the subglacial drainage system substantially affect patterns of flow and erosion by this small cirque glacier.

Cosmogenic 10Be insights into the extent and chronology of the last deglaciation in Wester Ross, northwest Scotland

AbstractCosmogenic 10Be surface exposure ages for bedrock sites around Torridon and the Applecross Peninsula in Wester Ross, northwest Scotland, provide new insights into the Lateglacial transition. Accounting for postglacial weathering, six statistically comparable exposure ages give a late Younger Dryas (G‐1) exposure age of 11.8 ± 1.1 ka. Two further outliers are tentative pre‐Younger Dryas exposure ages of 13.4 ± 0.5 ka in Torridon, and 17.5 ± 1.2 ka in Applecross. The Younger Dryas exposure ages have compelling implications for the deglaciation of marginal Loch Lomond Stadial ice fields in Torridon and Applecross. Firstly, they conflict with predictions of restricted ice cover and rapid retreat based on modelling experiments and climate proxies, instead fitting a model of vertically extensive and prolonged ice coverage in Wester Ross. Secondly, they indicate that >2 m of erosion took place in the upper valleys of Torridon and Applecross during the Younger Dryas, implying a dominantly warm‐based glacial regime. Finally, the exposure ages have clarified that corrie (cirque) glaciers did not readvance in Wester Ross, following final deglaciation. Copyright © 2011 John Wiley & Sons, Ltd.

Late Pleistocene mountain glacier response to North Atlantic climate change in southwest Ireland

There is clear geomorphological and dating evidence to suggest that the mountains of western Ireland were sensitive to North Atlantic cooling episodes throughout the Lateglacial period. In the mountains of the Macgillycuddy’s Reeks of southwest Ireland we have reconstructed the dimensions and former Equilibrium Line Altitudes (ELAs) of two sets of palaeoglaciers which readvanced following the end of the Last Glacial maximum. The most extensive glacier readvance, the Outer Local Glaciation, produced valley glaciers covering an area of around 11.2 km 2. Cosmogenic nuclide exposure ages from two boulders on the Hags Teeth moraine marking this event provide ages of 17.1 ± 1.3 and 22.9 ± 1.5 ka. The difference in the two ages probably reflects cosmogenic nuclide inheritance in the sampled boulders. The less extensive readvance, the Inner Local Glaciation, formed cirque glaciers covering an area of 1.56 km 2. Cosmogenic nuclide exposure ages from two boulders on moraines marking this event provide ages of 15.1 ± 1.0 ka and 14.9 ± 1.8 ka. We hypothesise that these ages either represent a glacial response to cooling during the Lateglacial Interstadial (during the Older Dryas cold phase) or reflect inherited boulder ages from a paraglacial episode of enhanced rockfall following glacier recession of valley glaciers, and the moraines are Younger Dryas in age. These data provide the first examples in the British Isles where two Lateglacial advances are reconstructed and indicate the dynamic nature of glaciation in this area.

Dynamics of an alpine cirque glacier

Alpine cirques are excavated by glacial erosion, a process that depends in turn on the movement of ice by basal sliding. Cirque glacier flow is usually depicted as rotational sliding of a rigid block, but this model is based on little evidence and implies unorthodox glacier behavior given typical cirque dimensions. The small (∼1 km2), temperate West Washmawapta Glacier occupies an archetypal overdeepened and “armchair-shaped” cirque in the Canadian Rockies. We measured (1) the annual surface velocity field, (2) ice thickness, (3) sliding and internal deformation at one borehole, and (4) sliding in a marginal cavity. The glacier moves slowly, with surface velocities of 3 to 10 m/yr. The maximum ice thickness (∼185 m) occurs in the center of the cirque basin and roughly coincides with the position of greatest ice flux. Using our field measurements, a standard constitutive relation for ice, and simplifying assumptions related to the depth distribution of strain rates, we approximated the driving and resisting forces acting on sections of the glacier, and inferred the general pattern of basal sliding. Sliding is minimum in the center of the cirque and increases toward the margins, especially up the stoss side of the riegel. Internal deformation accounts for all motion in the cirque center, even if an unusually low viscosity for temperate ice is assumed. Basal shear stresses tend toward 105 Pa everywhere, a typical value for mountain glaciers. Transverse and longitudinal straining are significant in some parts of the glacier. Although a component of rotational flow must occur internally, the glacier does not conform to the rotational sliding model in any essential respect.