scholarly journals Late Pleistocene climate conditions in the north Chilean Andes drawn from a climate–glacier model

2000 ◽  
Vol 46 (155) ◽  
pp. 622-632 ◽  
Author(s):  
Christoph Kull ◽  
Martin Grosjean
Keyword(s):  
Late Pleistocene ◽  
Cross Sections ◽  
Summer Precipitation ◽  
Late Glacial ◽  
Winter Precipitation ◽  
Test Area ◽  
Balance Model ◽  
Northern Chile ◽  
Equilibrium Line Altitude ◽  
Climate Conditions

AbstractA climate–glacier model was used to reconstruct Late-glacial climate conditions from two case-study glaciers at 18° and 22° S in the arid (sub)tropical western Andes of northern Chile. The model uses (i) the geometry of the Late-glacial maximum glaciation, (ii) modern diurnal and annual cycles, amplitudes and lapse rates of the climate, (iii) empirical–statistical sublimation, melt and accumulation models developed for this area, and (iv) dynamic ice flow through two known cross-sections for steady-state conditions. The model is validated with modern conditions and compares favorably with the glaciological features of today. The mass-balance model calculates the modern equilibrium-line altitude at 18° S as high as 5850 m (field data 5800 m), whereas no glaciers exist in the fully arid southern area at 22° S despite altitudes above 6000 m and continuous permafrost. For Late-glacial times, the model results suggest a substantial increase in tropical summer precipitation (ΔP = +840 (− 50/+ 10) mm a−1 for the northern test area; +1000 (− 10/+ 30) mm a−1 for the southern test area) and a moderate temperature depression (ΔT = −4.4 (− 0.1/+ 0.2) °C at 18° S; −3.2 (±0.1) °C at 22° S). Extratropical frontal winter precipitation (June–September) was <15% of the total annual precipitation. A scenario with higher winter precipitation from the westerlies circulation belt does not yield a numerical solution which matches the observed geometry of the glaciers. Therefore, we conclude that an equatorward displacement of the westerlies must be discarded as a possible explanation for the late Pleistocene glaciation in the Andes of northern Chile.

Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3He dating

2014 ◽  
Vol 82 (1) ◽  
pp. 209-221 ◽  
Author(s):  
Pierre-Henri Blard ◽  
Jérôme Lave ◽  
Kenneth A. Farley ◽  
Victor Ramirez ◽  
Nestor Jimenez ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Late Glacial ◽  
Glacial Period ◽  
Tropical Andes ◽  
Equilibrium Line Altitude ◽  
Glacial Retreat ◽  
Late Glacial Period ◽  
Cold Episode ◽  
Glacial Landforms ◽  
Exposure Ages

AbstractThis work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod.

scholarly journals Paleoclimatic interpretation of the early Late-glacial glacier in the Gschnitz valley, central Alps, Austria

1999 ◽  
Vol 28 ◽  
pp. 135-140 ◽  
Author(s):  
Hanns Kerschner ◽  
Susan Ivy-Ochs ◽  
Christian Schlüchter
Keyword(s):  
Cross Sections ◽  
Climate Models ◽  
Younger Dryas ◽  
Late Glacial ◽  
Point Of View ◽  
Central Alps ◽  
Equilibrium Line Altitude ◽  
Glacial Chronology ◽  
The Alps ◽  
Early Late

AbstractThe former glacier at the type locality of the “Gschnitz Stadial” of the Alpine Late-glacial chronology is interpreted from a paleoglaciological and paleoclimatological point of view. The equilibrium-line altitude, ice flux through selected cross sections and mass-balance gradients are calculated from reconstructed glacier topography. They are used to determine total net ablation and accumulation and precipitation under the assumption of steady-state. The former temperature at the ELA and temperature change is estimated using various glacier—climate models. Precipitation was less than one-third of today’s values, and summer temperature was roughly 10°C lower than today. The climate during the Gschnitz Stadial appears to have been cold and continental, and was more similar to full glacial conditions than to the Younger Dryas climate in the Alps. This is further evidence for an older age of the Gschnitz Stadial.

scholarly journals Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes

2015 ◽  
Vol 11 (2) ◽  
pp. 603-636 ◽  
Author(s):  
C. Bravo ◽  
M. Rojas ◽  
B. M. Anderson ◽  
A. N. Mackintosh ◽  
E. Sagredo ◽  
...  
Keyword(s):  
New Zealand ◽  
Mass Balance ◽  
Southern Hemisphere ◽  
Equilibrium Line ◽  
Balance Model ◽  
Glacier Mass Balance ◽  
Equilibrium Line Altitude ◽  
Climate Conditions ◽  
Precipitation Changes ◽  
Autumn And Winter

Abstract. Glacier behaviour during the mid-Holocene (MH, 6000 year BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeo-climatic signals. We examine the climatic forcing of glacier expansion in the MH by evaluating modelled glacier equilibrium line altitude (ELA) and climate conditions during the MH compared with pre-industrial time (PI, year 1750) in the mid latitudes of the Southern Hemisphere, specifically in Patagonia and the South Island of New Zealand. Climate conditions for the MH are obtained from PMIP2 models simulations, which in turn force a simple glacier mass balance model to simulate changes in equilibrium-line altitude during this period. Climate conditions during the MH show significantly (p ≤ 0.05) colder temperatures in summer, autumn and winter, and significantly (p ≤ 0.05) warmer temperatures in spring. These changes are a consequence of insolation differences between the two periods. Precipitation does not show significant changes, but exhibits a temporal pattern with less precipitation from August to September and more precipitation from October to April during the MH. In response to these climatic changes, glaciers in both analysed regions have an ELA that is 15–33 m lower than PI during the MH. The main causes of this difference are the colder temperature during the MH, reinforcing previous results that mid-latitude glaciers are more sensitive to temperature change compared to precipitation changes. Differences in temperature have a dual effect on mass balance. First, during summer and early autumn less energy is available for melting. Second in late autumn and winter, lower temperatures cause more precipitation to fall as snow rather than rain, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed in the mid Holocene in both South America and New Zealand.

Geomorphic and sedimentary responses of the Bull Creek Valley (Southern High Plains, USA) to Pleistocene and Holocene environmental change

2016 ◽  
Vol 85 (1) ◽  
pp. 118-132 ◽  
Author(s):  
Hanna M. Arauza ◽  
Alexander R. Simms ◽  
Leland C. Bement ◽  
Brian J. Carter ◽  
Travis Conley ◽  
...  
Keyword(s):  
Environmental History ◽  
Late Pleistocene ◽  
Environmental Conditions ◽  
Late Glacial ◽  
High Plains ◽  
Climate Conditions ◽  
Fluvial Terraces ◽  
Sedimentary Sequences ◽  
New Information ◽  
Bull Creek

Fluvial geomorphology and stratigraphy often reflect past environmental and climate conditions. This study examines the response of Bull Creek, a small ephemeral creek in the Oklahoma panhandle, to environmental conditions through the late Pleistocene and Holocene. Fluvial terraces were mapped and their stratigraphy and sedimentology documented throughout the course of the main valley. Based on their elevations, terraces were broadly grouped into a late-Pleistocene fill terrace (T3) and two Holocene fill-cut terrace sets (T2 and T1). Terrace systems are marked by similar stratigraphies recording the general environmental conditions of the time. Sedimentary sequences preserved in terrace fills record the transition from a perennial fluvial system during the late glacial period and the Younger Dryas to a semiarid environment dominated by loess accumulation and punctuated by flood events during the middle to late Holocene. The highest rates of aeolian accumulation within the valley occurred during the early to middle Holocene. Our data provide significant new information regarding the late-Pleistocene and Holocene environmental history for this region, located between the well-studied Southern and Central High Plains of North America.

scholarly journals Temperature reduction and local last glaciation maximum (LLGM) : the example of the east-Andean Cordillera around Cochabamba, Bolivia (17°S)

2006 ◽  
Vol 61 (2) ◽  
pp. 91-106 ◽  
Author(s):  
S. Imhof ◽  
J. H. May ◽  
H. Veit ◽  
C. Kull ◽  
M. Grosjean
Keyword(s):  
Climate Model ◽  
Late Glacial ◽  
Cold Climate ◽  
Age Dating ◽  
Shear Stresses ◽  
Equilibrium Line Altitude ◽  
Climate Conditions ◽  
The North ◽  
Andean Cordillera ◽  
Low Mass

Abstract. This study presents results from a glacier-climate model that reconstructed glacio-climatological conditions during the last local glaciation maximum (LLGM) in the Cordillera to the north of Cochabamba (17°15'S, 66°15'W), Bolivia. Results emphasize the temperature-sensitivity of glaciers on the eastern slope of the Cordillera Oriental. Maximum glacier advances appear to have been caused by a massive cooling of about 6.5°C while annual preeipitation was about 300 mm higher than today (850 mm/yr). Modeling results indicate maximum glacial advances during cold phases such as MIS 2 (25–18 kyr B.P.) and minor advances during late glacial cool events (12–10 kyr B.P.). This chronology is supported by exposure age dating results. Further evidence may be found in the low AAR-values (accumulation area ratio) which indicate low mass balance gradients and therefore cold climate conditions. Modeled basal shear stresses smaller than 1 bar exelude extremely «cold-dry» or «warm-wet» conditions. The spatial pattern of regional paleo-ELA's (equilibrium line altitude). with higher ELAs in the western part of the study area, reflects a strong east-west gradient in paleoprecipitation. Easterly summer preeipitation is suggested to be the reason for this phenomenon. These results are in agreement with other studies of the east-Andean slope, indicating temperature as the driving factor for maximum glacier advances in northwestern Argentina.

scholarly journals Analysis of the Surface Mass Balance for Deglacial Climate Simulations

2020 ◽  
Author(s):  
Marie-Luise Kapsch ◽  
Uwe Mikolajewicz ◽  
Florian Andreas Ziemen ◽  
Christian B. Rodehacke ◽  
Clemens Schannwell
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Data Set ◽  
Surface Mass ◽  
Climate Conditions

Abstract. Most studies analyzing changes in the surface mass balance (SMB) of the Greenland ice sheet are limited to the last century, due to the availability of observations and the computational limitations of regional climate modeling. Using transient simulations with a comprehensive Earth System Model (ESM) we extend previous research and study changes in the SMB and equilibrium line altitude (ELA) for deglacial climate conditions. An energy balance model (EBM) is used to downscale atmospheric processes. It determines the SMB on higher spatial resolution and allows to resolve SMB variations due to topographic gradients not resolved by the ESM. An evaluation for historical climate conditions (1980–2010) shows that derived SMBs compare well with SMBs from regional modeling. Throughout the deglaciation changes in insolation dominate the Greenland SMB: 1) The increase in insolation and associated warming early in the deglaciation result in an ELA and SMB increase. The SMB increase is caused by compensating effects of melt and accumulation, as a warmer atmosphere precipitates more. After 13 ka before present (BP) melt begins to dominate and the SMB decreases. 2) The decline in insolation after 9 ka BP leads to an increasing SMB and decreasing ELA. Superimposed on these long-term changes are episodes of significant SMB/ELA decreases, related to slowdowns of the Atlantic Meridional Overturning Circulation (AMOC) that lead to cooling over most of the Northern Hemisphere. To study associated changes in the ice sheet geometry, the SMB data set is made available to the ice sheet modeling community.

scholarly journals Exposure dating of Late Glacial and pre-LGM moraines in the Cordon de Doña Rosa, Northern/Central Chile (~31° S)

2007 ◽  
Vol 3 (1) ◽  
pp. 1-14 ◽  
Author(s):  
R. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
Austral Summer ◽  
Summer Precipitation ◽  
Late Glacial ◽  
Central Andes ◽  
Winter Precipitation ◽  
Tropical Circulation ◽  
Central Chile ◽  
Exposure Dating ◽  
Quaternary Glaciation ◽  
Southern Central

Abstract. Despite the important role of the Central Andes (15–30° S) for climate reconstruction, knowledge about the Quaternary glaciation is very limited due to the scarcity of organic material for radiocarbon dating. We applied 10Be surface exposure dating (SED) on 22 boulders from moraines in the Cordon de Doña Rosa, Northern/Central Chile (~31° S). The results show that several glacial advances in the southern Central Andes occurred during the Late Glacial between ~14.7±1.5 and 11.6±1.2 ka. A much more extensive glaciation is dated to ~32±3 ka, predating the temperature minimum of the global LGM (Last Glacial Maximum: ~20 ka). Reviewing these results in the paleoclimatic context, we conclude that the Late Glacial advances were most likely caused by an intensification of the tropical circulation and a corresponding increase in summer precipitation. High-latitude temperatures minima, e.g. the Younger Dryas (YD) and the Antarctic Cold Reversal (ACR) may have triggered individual advances, but current systematic exposure age uncertainties limit precise correlations. The absence of LGM moraines indicates that moisture advection was too limited to allow significant glacial advances at ~20 ka. The tropical circulation was less intensive despite the maximum in austral summer insolation. Winter precipitation was apparently also insufficient, although pollen and marine studies indicate a northward shift of the westerlies at that time. The dominant pre-LGM glacial advances in Northern/Central Chile at ~32 ka required lower temperatures and increased precipitation than today. We conclude that the westerlies were more intense and/or shifted equatorward, possibly due to increased snow and ice cover at higher southern latitudes coinciding with a minimum of insolation.

Sensitivities of the equilibrium line altitude to temperature and precipitation changes along the Andes

2014 ◽  
Vol 81 (2) ◽  
pp. 355-366 ◽  
Author(s):  
Esteban A. Sagredo ◽  
Summer Rupper ◽  
Thomas V. Lowell
Keyword(s):  
Spatial Variability ◽  
Spatial Scales ◽  
Equilibrium Line ◽  
Balance Model ◽  
Equilibrium Line Altitude ◽  
Climate Conditions ◽  
Temperature And Precipitation ◽  
The Andes ◽  
Mean Climate ◽  
Precipitation Changes

AbstractEquilibrium line altitudes (ELAs) of alpine glaciers are sensitive indicators of climate change and have been commonly used to reconstruct paleoclimates at different temporal and spatial scales. However, accurate interpretations of ELA fluctuations rely on a quantitative understanding of the sensitivity of ELAs to changes in climate. We applied a full surface energy- and mass-balance model to quantify ELA sensitivity to temperature and precipitation changes across the range of climate conditions found in the Andes. Model results show that ELA response has a strong spatial variability across the glaciated regions of South America. This spatial variability correlates with the distribution of the present-day mean climate conditions observed along the Andes. We find that ELAs respond linearly to changes in temperature, with the magnitude of the response being prescribed by the local lapse rates. ELA sensitivities to precipitation changes are nearly linear and are inversely correlated with the emissivity of the atmosphere. Temperature sensitivities are greatest in the inner tropics; precipitation becomes more important in the subtropics and northernmost mid-latitudes. These results can be considered an important step towards developing a framework for understanding past episodes of glacial fluctuations and ultimately for predicting glacier response to future climate changes.

Late Pleistocene Piñon Pines in the Chihuahuan Desert

1981 ◽  
Vol 15 (3) ◽  
pp. 278-290 ◽  
Author(s):  
Ronald M. Lanner ◽  
Thomas R. Van Devender
Keyword(s):  
Late Pleistocene ◽  
Chihuahuan Desert ◽  
El Paso ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Reduced Frequency ◽  
Winter Temperatures ◽  
Northern Edge ◽  
Summer Temperatures ◽  
In Trans

AbstractExamination of late Pleistocene packrat middens from the northern and central Chihuahuan Desert disclosed macrofossils of Colorado piñon (Pinus edulis) and Texas piñon (P. remota). Radiocarbon dating indicates that Texas piñon was widespread in Trans-Pecos Texas and northeastern Mexico between 30,000 and 11,000 yr B.P. Today it is found in small refugia east of its former range. In the late Pleistocene Colorado piñon occurred at lower elevations on the northern edge of the Chihuahuan Desert. Both species occurred in the Hueco Mountains, near El Paso, Texas. No clear evidence was found of the presence of Mexican piñon (P. cembroides), though today it is abundant in the Davis and Chisos Mountains. A paleoclimate is postulated that had the following characteristics: increased winter precipitation from Pacific frontal sources, reduced summer temperatures and precipitation, and milder winter temperatures due to a reduced frequency of Arctic airmass incursion. Winter precipitation appears to have decreased from north to south, while winter temperatures, and, possibly, summer precipitation, increased from north to south. During the late Pleistocene, the northern Chihuahuan Desert was dominated by woodlands of piñon pines, junipers, and oaks. The desert-scrub communities that characterize the area today are a Holocene phenomenon.

scholarly journals Impact of climatic changes in the Late Pleistocene on migrations and extinctions of mammals in Europe: four case studies

2016 ◽  
Author(s):  
Mateusz Baca ◽  
Adam Nadachowski ◽  
Grzegorz Lipecki ◽  
Paweł Mackiewicz ◽  
Adrian Marciszak ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Climate Changes ◽  
Late Glacial ◽  
Mammal Species ◽  
Mammuthus Primigenius ◽  
Climate Conditions ◽  
Local Extinctions ◽  
The Last Glacial Maximum ◽  
The Last Glacial ◽  
Woolly Mammoth

Climate changes that occurred during the Late Pleistocene have profound effects on the distribution of many plant and animal species and influenced the formation of contemporary faunas and floras of Europe. The course and mechanisms of responses of species to the past climate changes are now being intensively studied by the use of direct radiocarbon dating and genetic analyses of fossil remains. Here, we review the advances in understanding these processes by the example of four mammal species: woolly mammoth (Mammuthus primigenius), cave bear (Ursus spelaeus s. l.), saiga antelope (Saiga tatarica) and collared lemmings (Dicrostonyx ssp.). The cases discussed here as well as others show that the migrations, range shifts and local extinctions were the main responses to climate changes and that the dynamics of these climate driven processes were much more profound than it was previously thought. Each species reacted by its individual manner, which depended on its biology and adaptation abilities to the changing environment and climate conditions. The most severe changes in European ecosystems that affected the largest number of species took place around 33–31 ka BP, during the Last Glacial Maximum 22–19 ka BP and the Late Glacial warming 15–13 ka BP.

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