Exposure age chronology of the last glaciation in the eastern Pyrenees

2008 ◽  
Vol 69 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Magali Delmas ◽  
Yanni Gunnell ◽  
Régis Braucher ◽  
Marc Calvet ◽  
Didier Bourlès
Keyword(s):  
Ice Cores ◽  
Sampling Strategy ◽  
Large Change ◽  
Equilibrium Line Altitude ◽  
Ice Cap ◽  
Eastern Pyrenees ◽  
Relative Chronology ◽  
Geomorphological Map ◽  
Glacial Landforms

We present a chronology of ice recession in the eastern Pyrenees based onin situ-produced10Be data obtained from the Têt paleoglacier complex. The sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms. Results indicate that the last maximum ice advance occurred late (i.e., during Marine Isotope Stage 2) compared to the chronology currently established for the rest of the Pyrenees. Despite debatable evidence for a glacial readvance during the Oldest Dryas stade, ice-cap melt-out was rapid, residual cirque glaciers having disappeared by the Allerød interstade. This is consistent both with North Atlantic excursions established by the Greenland ice cores and paleoenvironmental data for the region. The rapid response of the east-Pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger Pyrenean ice fields, to the dry Mediterranean climate, and to topography-related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass. Possible sources of age uncertainty are discussed in the context of sampling design for single-nuclide (10Be) dating of landform sequences in formerly glaciated landscapes.

scholarly journals Glacial Geomorphology and Preliminary Glacier Reconstruction in the Jablanica Mountain, Macedonia, Central Balkan Peninsula

Geosciences ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 270 ◽  
Author(s):  
Marjan Temovski ◽  
Balázs Madarász ◽  
Zoltán Kern ◽  
Ivica Milevski ◽  
Zsófia Ruszkiczay-Rüdiger
Keyword(s):  
19Th Century ◽  
Central Europe ◽  
Balkan Peninsula ◽  
Equilibrium Line Altitude ◽  
Glacial Geomorphology ◽  
Geomorphological Map ◽  
Glacier Reconstruction ◽  
Glacial Landforms ◽  
The 19Th Century ◽  
Scarce Data

Although glacial landforms on the Balkan Peninsula have been studied since the 19th century, only scarce data are available about the extent of the former glaciations in the Central Balkan Peninsula, the transition zone between the Mediterranean and Central Europe. Glacial features of the Jablanica Mt. were mapped, described and classified into morphostratigraphic units. A revised glacio-geomorphological map was produced and glacial landforms were assigned to six morphostratigraphic units. Ten primary and two secondary cirques were identified in the upper parts of the studied valleys, while downstream the valleys were steep and glacially shaped with several glacial steps and thresholds. Cirque and valley morphology indicate that subglacial deepening was limited within the cirques and was more intensive in the valley sections during more extensive glacial phases. The largest reconstructed glaciers were 4.6–7 km long, while the last cirque glaciers were only a few hundred meters long. Using morphostratigraphic data, a glacier reconstruction was carried out for the largest mapped glacial extent. On the basis of glacial geomorphology, a former equilibrium-line altitude (ELA) of ~1800 m and glacier cover of 22.6 km2 were estimated during this stage. The local ELA values were compared to the regional ELA record and enabled to tentatively attribute a MIS 6 age for the reconstructed maximum ice extent in the study area.

scholarly journals First in situ record of decadal glacier mass balance (2003–2014) from the Bhutan Himalaya

2016 ◽  
Vol 57 (71) ◽  
pp. 289-294 ◽  
Author(s):  
Phuntsho Tshering ◽  
Koji Fujita
Keyword(s):  
Mass Balance ◽  
Direct Method ◽  
Eastern Himalaya ◽  
Glacier Mass Balance ◽  
Differential Gps ◽  
Humid Climate ◽  
Equilibrium Line Altitude ◽  
The Past ◽  
Southeastern Tibet

AbstractThis study presents the first decadal mass-balance record of a small debris-free glacier in the Bhutan Himalaya, where few in situ measurements have been reported to date. Since 2003 we have measured the mass balance of Gangju La glacier, which covers an area of 0.3km2 and extends from 4900 to 5200ma.s.l., using both differential GPS surveys (geodetic method) and stake measurements (direct method). The observed mass balance ranged from –1.12 to –2.04mw.e. a–1 between 2003 and 2014. The glacier exhibited much greater mass loss than neighbouring glaciers in the eastern Himalaya and southeastern Tibet, which are expected to be sensitive to climate change due to the monsooninfluenced humid climate. Observed mass-balance profiles suggest that the equilibrium-line altitude has been higher than Gangju La glacier since 2003, implying that the entire glacier has experienced net ablation for at least the past decade.

Comparison of 105 Years of Oxygen Isotope and Insoluble Impurity Profiles from the Devon Island and Camp Century Ice Cores

1979 ◽  
Vol 11 (3) ◽  
pp. 299-305 ◽  
Author(s):  
David A. Fisher
Keyword(s):  
Oxygen Isotope ◽  
Flow Line ◽  
Ice Cores ◽  
Devon Island ◽  
Ice Cap ◽  
Particulate Concentration ◽  
The Difference ◽  
Impurity Profiles ◽  
Level Lowering ◽  
Present Site

Oxygen-isotope profiles for the Devon Island ice cap and Camp Century Greenland are affected by a number of variables, some of which must have been the same for both sites. The two δ(18O) records spanning about 120,000 years are brought into relative alignment by comparison of major δ features, and subsequent verification that the insoluble particulate concentration records were also in phase for this alignment. The difference between the δ profiles is shown to be mainly a function of the altitude of the accumulation area for Camp Century. This altitude seems to have been higher than present for the last 100,000 years, suggesting the present flow line through the site has never been shorter. The maximum altitude for the Camp Century accumulation area is 1500 m above the present site and is almost synchronous with the maximum in particulate concentration that occurs at 16,000 yr B.P. The synchronism is likely due to the maximum sea-level lowering that exposed vast areas of continental shelf to wind erosion.

scholarly journals The Hans Tausen drill: design, performance, further developments and some lessons learned

2007 ◽  
Vol 47 ◽  
pp. 89-98 ◽  
Author(s):  
Sigfús J. Johnsen ◽  
Steffen Bo Hansen ◽  
Simon G. Sheldon ◽  
Dorthe Dahl-Jensen ◽  
Jørgen P. Steffensen ◽  
...  
Keyword(s):  
Mechanical Design ◽  
Ice Cores ◽  
Lessons Learned ◽  
Niels Bohr ◽  
Deep Drilling ◽  
Niels Bohr Institute ◽  
Design Performance ◽  
Ice Cap ◽  
Drill Design

AbstractIn the mid-1990s, excellent results from the GRIP and GISP2 deep drilling projects in Greenland opened up funding for continued ice-coring efforts in Antarctica (EPICA) and Greenland (NorthGRIP). The Glaciology Group of the Niels Bohr Institute, University of Copenhagen, was assigned the task of providing drilling capability for these projects, as it had done for the GRIP project. The group decided to further simplify existing deep drill designs for better reliability and ease of handling. The drill design decided upon was successfully tested on Hans Tausen Ice Cap, Peary Land, Greenland, in 1995. The 5.0m long Hans Tausen (HT) drill was a prototype for the ~11m long EPICA and NorthGRIP versions of the drill which were mechanically identical to the HT drill except for a much longer core barrel and chips chamber. These drills could deliver up to 4m long ice cores after some design improvements had been introduced. The Berkner Island (Antarctica) drill is also an extended HT drill capable of drilling 2 m long cores. The success of the mechanical design of the HT drill is manifested by over 12 km of good-quality ice cores drilled by the HT drill and its derivatives since 1995.

scholarly journals Glaciological Investigations of the Tropical Quelccaya Ice Cap, Peru

1980 ◽  
Vol 25 (91) ◽  
pp. 69-84 ◽  
Author(s):  
Lonnie G. Thompson
Keyword(s):  
Rainy Season ◽  
Ice Core ◽  
Ice Cores ◽  
Dry Season ◽  
Radioactive Material ◽  
Polar Regions ◽  
Near Surface ◽  
Ice Cap ◽  
Activity Measurements ◽  
Quelccaya Ice Cap

AbstractGlaciological results of the continuing investigations of the Quelccaya ice cap located at lat. 13° 56’ S., long. 70° 50’ W., in the Cordillera Oriental of southern Peru are presented. Ice cores to a depth of 15 m have been retrieved from the summit dome (5650 m), middle dome (5543 m), and south dome (5480 m) and sampled in detail for microparticle, oxygen-isotope, and total-β-activity measurements. Results of these core analyses indicate that although the summit of this ice cap is only 300 m above the annual snow line and the firn is temperate, an interpretable stratigraphic record is preserved. The marked seasonal ice stratigraphy is produced by the marked seasonal variation in regional precipitation. High concentrations of microparticles and β- radioactive material occur during the dry season (May-August). Microparticles deposited during the rainy season are larger than those deposited during the dry season. On the Quelccaya ice cap the most negative δ18O values occur during the warmer rainy season (the opposite occurs in polar regions). The near-surface mean δ value of – 21‰ is remarkably low for this tropical site where the measured mean annual air temperature is – 3°C The seasonality of the microparticles, total β activity, and isotope ratios offers the prospect of a climatic ice-core record from this tropical ice cap.

scholarly journals How Biased Is Aircraft Cloud Sampling?

2016 ◽  
Vol 33 (1) ◽  
pp. 185-189 ◽  
Author(s):  
Paul R. Field ◽  
Kalli Furtado
Keyword(s):  
Order Statistics ◽  
Sampling Strategy ◽  
Model Testing ◽  
Resource Limitations ◽  
Cloud Properties ◽  
Gamma Distributions

AbstractAircraft are the dominant method for in situ sampling of cloud properties. Resource limitations mean that aircraft tend to follow a sampling strategy when there is more than one cloud from which to choose. This can result in biased cloud statistics that are used for parameterization development and model testing. In this study, order statistics are used to estimate the potential magnitude of this bias when a strategy based on choosing the larger cloud is employed. It is found for cloud properties following gamma distributions that a typical bias of a factor of 1.5 can result when the larger of two clouds is repeatedly chosen for sampling.

scholarly journals Seasonal and annual mass balances of Mera and Pokalde glaciers (Nepal Himalaya) since 2007

2013 ◽  
Vol 7 (4) ◽  
pp. 3337-3378 ◽  
Author(s):  
P. Wagnon ◽  
C. Vincent ◽  
Y. Arnaud ◽  
E. Berthier ◽  
E. Vuillermoz ◽  
...  
Keyword(s):  
Mass Balance ◽  
Cross Sections ◽  
Mass Balances ◽  
Equilibrium Line Altitude ◽  
Nepal Himalaya ◽  
Limited Mass ◽  
In Situ Observations ◽  
The Mean ◽  
Southern Flank

Abstract. In the Everest region, Nepal, ground-based monitoring programs were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940 m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430 m a.s.l., ∼ 25 km North of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large inter-annual variability with glacier-wide mass balances ranging from −0.77± 0.40 m w.e. in 2011–2012 (Equilibrium-line altitude (ELA) at ∼ 6055 m a.s.l.) to + 0.46 ± 0.40 m w.e. in 2010–2011 (ELA at ∼ 5340 m a.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of −0.10± 0.40 m w.e. yr−1 since 2007. Ice fluxes measured at two distinct transverse cross sections at ∼ 5350 m a.s.l. and ∼ 5520 m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed region-wide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilized snow likely being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of −0.72 and −0.26 ± 0.40 m w.e. yr−1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate.

scholarly journals 21st century fate of the Mocho-Choshuenco ice cap in southern Chile

2020 ◽  
Author(s):  
Matthias Scheiter ◽  
Marius Schaefer ◽  
Eduardo Flández ◽  
Deniz Bozkurt ◽  
Ralf Greve
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Lake District ◽  
Equilibrium Line Altitude ◽  
Ice Dynamics ◽  
Ice Volume ◽  
Ice Cap ◽  
Global Circulation Models

Abstract. Glaciers and ice caps are thinning and retreating along the entire Andes ridge, and drivers of this mass loss vary between the different climate zones. The southern part of the Andes (Wet Andes) has the highest abundance of glaciers in number and size, and a proper understanding of ice dynamics is important to assess their evolution. In this contribution, we apply the ice sheet model SICOPOLIS to the Mocho-Choshuenco ice cap in the Chilean Lake District (40° S, 72° W, Wet Andes) to reproduce its current state and to project its evolution until the end of the 21st century under different global warming scenarios. First, we create a model spin-up using surface mass balance data observed on the south-eastern catchment, extrapolating them to the whole ice cap using an exposition-dependent parameterization. This spin-up is able to reproduce the most important present-day glacier features. Based on the spin-up, we then run the model 80 years into the future, forced by projected surface temperature anomalies from different global circulation models under different radiative pathway scenarios to obtain estimates of the ice cap's state by the end of the 21st century. The mean projected ice volume losses are 25 ± 19 % (RCP2.6), 64 ± 14 % (RCP4.5) and 94 ± 3 % (RCP8.5) with respect to the ice volume estimated by radio-echo sounding data from 2013. We estimate the uncertainty of our projections based on the spread of the results when forcing with different global climate models and on the uncertainty associated with the variation of the equilibrium line altitude with temperature change. Considering our results, we project an considerable deglaciation of the Chilean Lake District by the end of the 21st century.

scholarly journals Periglacial Features on the Margins of a Receding Plateau Ice Cap, Lyngen, North Norway

1981 ◽  
Vol 27 (97) ◽  
pp. 492-496 ◽  
Author(s):  
W. Brian Whalley ◽  
John E. Gordon ◽  
David L. Thompson
Keyword(s):  
Melting Point ◽  
Ice Cap ◽  
Basal Ice ◽  
Relative Chronology ◽  
Absolute Dating ◽  
Pressure Melting ◽  
North Norway

AbstractSome features around the perimeter of the Balgesvarri plateau ice cap are described. Sorted stone circles were found beneath a slowly retreating ice margin, the basal ice in this area appears to be below the pressure-melting point. No absolute dating of features was possible but a relative chronology is suggested.

An Early Tertiary Outcrop in North-Central Baffin Island, Northwest Territories, Canada: Environment and Significance

1972 ◽  
Vol 9 (3) ◽  
pp. 233-238 ◽  
Author(s):  
J. T. Andrews ◽  
J. D. Ives ◽  
G. K. Guennel ◽  
J. L. Wray
Keyword(s):  
Laminated Sediments ◽  
Coarse Grained ◽  
Baffin Island ◽  
Vertical Movements ◽  
North Central ◽  
Baffin Bay ◽  
Ice Cap ◽  
Early Tertiary ◽  
Warm Temperate

A thin, impure limestone was found in situ on Precambrian bedrock at latitude 70°36.6′ N and longitude 75°20′ W some 26 km northwest of the Barnes Ice Cap. The unit consists of undulating laminations composed of alternating fine- and coarse-grained sediment, which are interpreted as a series of algal mats or algal-laminated sediments. An analysis of enclosed palynomorphs indicates the presence of Ulmus, Taxodiutm, Liriodendron, Carpinus, and Engelhardtia plus other genera. On the basis of the microflora a Paleogene age is assigned to the unit. The climate at that time was warm-temperate and the environment suggested is a freshwater marsh or swamp. The outcrop is restricted to a single hill summit and its location suggests considerable Neogene geomorphological activity, primarily river-cutting associated with vertical movements along the western margin of the Davis Strait/Baffin Bay Tift.

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