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.

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

2006 ◽  
Vol 2 (5) ◽  
pp. 847-878 ◽  
Author(s):  
R. Zech ◽  
C. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
High Latitude ◽  
Austral Summer ◽  
Late Glacial ◽  
Central Andes ◽  
Climate Modelling ◽  
Tropical Circulation ◽  
Central Chile ◽  
Exposure Dating ◽  
Summer Insolation ◽  
Moisture Advection

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 BP. A much more extensive glaciation is dated to ~32±3 ka BP, predating the temperature minimum of the global LGM (Last Glacial Maximum: ~20 ka BP). Reviewing these results in the paleoclimatic context, we note that the Late Glacial advances coincide with (i) lower temperatures during the Younger Dryas (YD) and the Antarctic Cold Reversal (ACR), (ii) the intensification of the tropical circulation and a corresponding increase in summer precipitation and (iii) a minimum in austral summer insolation favouring reduced ablation. The absence of LGM moraines indicates that moisture advection was too limited to allow significant glacial advances at ~20 ka BP. The tropical circulation was much 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 BP required lower temperatures and increased precipitation than today. They coincide with (i) a minimum of southern high-latitude insolation suggesting an equatorward shift of the westerlies due to increased snow and ice cover, (ii) a maximum winter insolation resulting in ocean-continental temperature and pressure gradients favouring moisture advection, (iii) minimum summer insolation suggesting lower temperatures and reduced ablation and (iv) low high-latitude temperatures corroborating that they affect subtropical and tropical temperatures. More glacier-climate modelling is necessary to quantify the influence of the various forcings on the dated glacial advances.

scholarly journals Early last glacial maximum in the southern Central Andes reveals northward shift of the westerlies at ~39 ka

2011 ◽  
Vol 7 (1) ◽  
pp. 41-46 ◽  
Author(s):  
R. Zech ◽  
J. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
Last Glacial Maximum ◽  
Central Andes ◽  
Glacial Maximum ◽  
Atmospheric Co2 ◽  
Dissolved Carbon ◽  
Last Glacial ◽  
Exposure Dating ◽  
Latitudinal Position ◽  
Southern Central ◽  
Southern Westerlies

Abstract. The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka), resulting in reduced deep ocean ventilation, accumulation of old dissolved carbon, and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

scholarly journals Timing and extent of late pleistocene glaciation in the arid Central Andes of Argentina and Chile (22°-41°S)

2017 ◽  
Vol 43 (2) ◽  
pp. 697 ◽  
Author(s):  
J. Zech ◽  
C. Terrizzano ◽  
E. García-Morabito ◽  
H. Veit ◽  
R. Zech
Keyword(s):  
Southern Oscillation ◽  
Co2 Concentration ◽  
Late Glacial ◽  
Central Andes ◽  
The North ◽  
Eastern Equatorial Pacific ◽  
Southern Central ◽  
Study Sites ◽  
Increasing Temperature ◽  
Exposure Ages

The arid Central Andes are a key site to study changes in intensity and movement of the three main atmospheric circulation systems over South America: the South American Summer Monsoon (SASM), the Westerlies and the El Niño Southern Oscillation (ENSO). In this semi-arid to arid region glaciers are particularly sensitive to precipitation changes and thus the timing of past glaciation is strongly linked to changes in moisture supply. Surface exposure ages from study sites between 41° and 22°S suggest that glaciers advanced: i) prior to the global Last Glacial Maximum (gLGM) at ~40 ka in the mid (26°- 30°S) and southern Central Andes (35°-41°S), ii) in phase with the gLGM in the northern and southern Central Andes and iii) during the late glacial in the northern Central Andes. Deglaciation started synchronous with the global rise in atmospheric CO2 concentration and increasing temperature starting at ~18 ka. The pre-gLGM glacial advances likely document enhanced precipitation related to the Southern Westerlies, which shifted further to the North at that time than previosuly assumed. During the gLGM glacial advances were favored by decreased temperatures in combination with increased humidity due to a southward shifted Intertropical Convergence Zone (ITCZ) and SASM. During the late-glacial a substantial increase in moisture can be explained by enhanced upper tropospheric easterlies as response to an intensified SASM and sustained La Niña-like conditions over the eastern equatorial Pacific that lead to glacial advances in the northern Central Andes and the lake level highstand Tauca (18-14 ka) on the Altiplano. In the southernmost Central Andes at 39º-41°S, further north at 31°S and in the northernmost Central Andes at 22°S glacial remnants even point to precipitation driven glaciations older than ~115 ka and 260 ka.

scholarly journals South-western Africa vegetation responses to atmospheric and oceanic changes during the last climatic cycle

2015 ◽  
Vol 11 (1) ◽  
pp. 345-376 ◽  
Author(s):  
D. H. Urrego ◽  
M. F. Sánchez Goñi ◽  
A. L. Daniau ◽  
S. Lechevrel ◽  
V. Hanquiez
Keyword(s):  
Austral Summer ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Relative Increase ◽  
Austral Winter ◽  
Last Interglacial ◽  
Ice Caps ◽  
Western Africa ◽  
Mis 5E ◽  
Mis 5

Abstract. Terrestrial and marine climatic tracers from marine core MD96-2098 collected in the southwestern African margin and spanning from 194 to 24 (thousand years before present) documented three pronounced expansions of Nama-Karoo and fine-leaved savanna during the last interglacial (Marine Isotopic Stage 5 – MIS 5). Nama-Karoo and fine-leaved savanna expansions were linked to increased aridity during the three warmest substadials of MIS 5. Enhanced aridity potentially resulted from a combination of reduced Benguela Upwelling System (BUS), expanded subtropical high-pressure cells, and reduced austral-summer precipitation due to a northward shift of the Intertropical Convergence Zone (ITCZ). Decreased austral-winter precipitation was likely linked to a southern displacement of the westerlies. In contrast, during glacial isotopic stages MIS 6, 4 and 3, Fynbos expanded at the expense of Nama-Karoo and fine-leaved savanna indicating a relative increase in precipitation probably concentrated during the austral winter months. Our record also suggested that warm-cold or cold-warm transitions between isotopic stages and substages were punctuated by short increases in humidity. Increased aridity during MIS 5e, 5c and 5a warm substages coincided with minima in both precessional index and global ice volume. On the other hand, austral-winter precipitation increases were associated with precession maxima at the time of well-developed northern-hemisphere ice caps.

scholarly journals Early last glacial maximum in the Southern Central Andes reveals northward shift of the westerlies at ~39 ka

2010 ◽  
Vol 6 (5) ◽  
pp. 1991-2004 ◽  
Author(s):  
R. Zech ◽  
J. Zech ◽  
C. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
Last Glacial Maximum ◽  
Central Andes ◽  
Glacial Maximum ◽  
Atmospheric Co2 ◽  
Dissolved Carbon ◽  
Last Glacial ◽  
Exposure Dating ◽  
Latitudinal Position ◽  
Southern Central ◽  
Southern Westerlies

Abstract. The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka), resulting in reduced deep ocean ventilation, accumulation of "old dissolved carbon", and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the Southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

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.

Surface exposure dating reveals MIS-3 glacial maximum in the Khangai Mountains of Mongolia

2014 ◽  
Vol 82 (2) ◽  
pp. 297-308 ◽  
Author(s):  
Henrik Rother ◽  
Frank Lehmkuhl ◽  
David Fink ◽  
Veit Nottebaum
Keyword(s):  
Central Asia ◽  
Winter Precipitation ◽  
Climatic Conditions ◽  
Study Region ◽  
Oxygen Isotope Stage ◽  
Central Mongolia ◽  
Geomorphological Mapping ◽  
Exposure Dating ◽  
Mis 3 ◽  
Southern Central

AbstractThis study presents results from geomorphological mapping and cosmogenic radionuclide dating (10Be) of moraine sequences at Otgon Tenger (3905 m), the highest peak in the Khangai Mountains (central Mongolia). Our findings indicate that glaciers reached their last maximum extent between 40 and 35 ka during Marine Oxygen Isotope Stage (MIS) 3. Large ice advances also occurred during MIS-2 (at ~ 23 and 17–16 ka), but these advances did not exceed the limits reached during MIS-3. The results indicate that climatic conditions during MIS-3, characterized by a cool-wet climate with a greater-than-today input from winter precipitation, generated the most favorable setting for glaciation in the study region. Yet, glacial accumulation also responded positively to the far colder and drier conditions of MIS-2, and again during the last glacial–interglacial transition when precipitation levels increased. Viewed in context of other Pleistocene glacial records from High Asia, the pattern of glaciation in central Mongolia shares some features with records from southern Central Asia and NE-Tibet (i.e. ice maxima during interstadial wet phases), while other features of the Mongolian record (i.e. major ice expansion during the MIS-2 insolation minimum) are more in tune with glacier responses known from Siberia and western Central Asia.

The Potential Impacts of Climate Change on Europe

1998 ◽  
Vol 9 (4) ◽  
pp. 365-381 ◽  
Author(s):  
Martin Beniston ◽  
Richard S. J. Tol
Keyword(s):  
Climate Change ◽  
Water Availability ◽  
Western Europe ◽  
Central And Eastern Europe ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Vegetation Patterns ◽  
Southern Central ◽  
Negative Impacts ◽  
Impacts Of Climate Change

GCMs project higher temperatures for all of Europe, with greater changes at higher latitudes. In Northern and Western Europe, winter precipitation may increase, and summer precipitation may remain unchanged. Different models show different changes for Southern, Central and Eastern Europe. Water resources follow roughly the same patterns, although higher temperatures increase the risk of summer droughts, particularly in Southern and Central Europe. In Western Europe, river floods may increase. Vegetation patterns may drastically change, with some species and communities expanding and other shrinking. Particularly vulnerable are ecosystems depending on northern cold, and ecosystems isolated by geography or human activity. On the whole, agriculture would seem to benefit from climatic change, although not-well-understood pests and water availability may alter this. Sea level rise would negatively affect low-lying coasts and deltas, which support important natural and human systems. In a warmer climate, cold-related health problems would decline, but heat-related ones would increase. Tentatively, the balance is reduced mortality. Less important climate-related diseases would, on balance, increase. Research on other sector has progressed less far; results show mixed positive and negative impacts. Expressing all impact in money and adding up suggests a light negative overall impact of climate change on Europe.

scholarly journals Increased aridity in southwestern Africa during the warmest periods of the last interglacial

2015 ◽  
Vol 11 (10) ◽  
pp. 1417-1431 ◽  
Author(s):  
D. H. Urrego ◽  
M. F. Sánchez Goñi ◽  
A.-L. Daniau ◽  
S. Lechevrel ◽  
V. Hanquiez
Keyword(s):  
Austral Summer ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Relative Increase ◽  
Pollen Record ◽  
Austral Winter ◽  
Last Interglacial ◽  
Ice Caps ◽  
Mis 5E ◽  
Mis 5

Abstract. Terrestrial and marine climatic tracers from marine core MD96-2098 were used to reconstruct glacial–interglacial climate variability in southwestern Africa between 194 and 24 thousand years before present. The pollen record documented three pronounced expansions of Nama-karoo and fine-leaved savanna during the last interglacial (Marine Isotopic Stage 5 – MIS 5). These Nama-karoo and fine-leaved savanna expansions were linked to increased aridity during the three warmest substadials of MIS 5. Enhanced aridity potentially resulted from a combination of reduced Benguela Upwelling, expanded subtropical high-pressure cells, and reduced austral-summer precipitation due to a northward shift of the Intertropical Convergence Zone. Decreased austral-winter precipitation was likely linked to a southern displacement of the westerlies. In contrast, during glacial isotopic stages MIS 6, 4 and 3, fynbos expanded at the expense of Nama-karoo and fine-leaved savanna indicating a relative increase in precipitation probably concentrated during the austral winter months. Our record also suggested that warm–cold or cold–warm transitions between isotopic stages and substages were punctuated by short increases in humidity. Increased aridity during MIS 5e, 5c and 5a warm substages coincided with minima in both precessional index and global ice volume. On the other hand, austral-winter precipitation increases were associated with precession maxima at the time of well-developed Northern Hemisphere ice caps.

RETROARC BASIN REORGANIZATION AND DIACHRONOUS ARIDIFICATION DURING PALEOGENE UPLIFT OF THE SOUTHERN CENTRAL ANDES

2016 ◽  
Author(s):  
Julie C. Fosdick ◽  
◽  
Barbara Carrapa ◽  
Barbara Carrapa ◽  
Ellen J. Reat ◽  
...  
Keyword(s):  
Central Andes ◽  
Southern Central
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