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1
Liakka, J., M. Löfverström e F. Colleoni. "The impact of the North American ice sheet on the evolution of the Eurasian ice sheet during the last glacial cycle". Climate of the Past Discussions 11, n. 6 (10 novembre 2015): 5203–41. http://dx.doi.org/10.5194/cpd-11-5203-2015.
Abstract (sommario):
Abstract. Modeling studies show that the massive ice sheet expanding over the North American and Eurasian continents in the last glacial cycle has a large impact on the atmospheric stationary waves and thus yielded a glacial climate distinctly different from the present. However, to what extent the two ice sheets influenced each others growth trajectories remains largely unexplored. In this study we investigate how ice sheets in North America influence the downstream evolution of the Eurasian ice sheet, using a thermomechanical ice-sheet model forced by climate data from snapshot simulations of three distinctly different phases of the last glacial cycle: the Marine Isotope Stages 5b, 4 and 2 (LGM). Our results suggest that changes in the North American paleo-topography may have had a large influence on evolution of the Eurasian ice sheet. In the MIS4 and LGM experiments, the Eurasian ice sheet migrates westward towards the Atlantic sector – largely consistent with geological data and contemporary ice-sheet reconstructions – due to a low wavenumber stationary wave response, which yields a cooling in Europe and a warming in northeastern Siberia. The expansion of the North American ice sheet between MIS4 and LGM amplifies the Siberian warm anomaly, which limits the glaciation there and may therefore help to explain the progressive westward migration of the Eurasian ice sheet over this time period. While the Eurasian ice sheet in the MIS4 and LGM experiments appears to be in equilibrium with the simulated climate conditions, the MIS5b climate forcing is too warm to grow an ice sheet. First-order sensitivity experiments suggest that most of the MIS5b ice sheet was established during preceding colder stages.
2
Liakka, Johan, Marcus Löfverström e Florence Colleoni. "The impact of the North American glacial topography on the evolution of the Eurasian ice sheet over the last glacial cycle". Climate of the Past 12, n. 5 (25 maggio 2016): 1225–41. http://dx.doi.org/10.5194/cp-12-1225-2016.
Abstract (sommario):
Abstract. Modeling studies have shown that the continental-scale ice sheets in North America and Eurasia in the last glacial cycle had a large influence on the atmospheric circulation and thus yielded a climate distinctly different from the present. However, to what extent the two ice sheets influenced each others' growth trajectories remains largely unexplored. In this study we investigate how an ice sheet in North America influences the downstream evolution of the Eurasian ice sheet, using a thermomechanical ice-sheet model forced by climate data from atmospheric snapshot experiments of three distinctly different phases of the last glacial cycle: the Marine Isotope Stages 5b, 4, and 2 (Last Glacial Maximum – LGM). Owing to the large uncertainty associated with glacial changes in the Atlantic meridional overturning circulation, each atmospheric snapshot experiment was conducted using two distinctly different ocean heat transport representations. Our results suggest that changes in the North American paleo-topography may have largely controlled the zonal distribution of the Eurasian ice sheet. In the MIS4 and LGM experiments, the Eurasian ice sheet migrates westward towards the Atlantic sector – largely consistent with geological data and contemporary ice-sheet reconstructions – due to a low wave number stationary wave response, which yields a cooling in Europe and a warming in northeastern Siberia. The expansion of the North American ice sheet between MIS4 and the LGM amplifies the Siberian warm anomaly, which limits the glaciation there and may therefore help explain the progressive westward migration of the Eurasian ice sheet in this time period. The ocean heat transport only has a small influence on the stationary wave response to the North American glacial topography; however, because temperature anomalies have a smaller influence on an ice sheet's ablation in a colder climate than in a warmer one, the impact of the North American glacial topography on the Eurasian ice-sheet evolution is reduced for colder surface conditions in the North Atlantic. While the Eurasian ice sheet in the MIS4 and the LGM experiments appears to be in equilibrium with the simulated climate conditions, the MIS5b climate forcing is too warm to grow an ice sheet in Eurasia. First-order sensitivity experiments suggest that the MIS5b ice sheet was established during preceding colder stages.
3
Van Meerbeeck, C. J., H. Renssen e D. M. Roche. "How did Marine Isotope Stage 3 and Last Glacial Maximum climates differ? Perspectives from equilibrium simulations". Climate of the Past Discussions 4, n. 5 (6 ottobre 2008): 1115–58. http://dx.doi.org/10.5194/cpd-4-1115-2008.
Abstract (sommario):
Abstract. Dansgaard-Oeschger events occurred frequently during Marine Isotope Stage 3 (MIS3), as opposed to the following MIS2 period, which included the Last Glacial Maximum (LGM). Transient climate model simulations suggest that these abrupt warming events in Greenland and the North Atlantic region are associated with a resumption of the Thermohaline Circulation (THC) from a weak state during stadials to a relatively strong state during interstadials. However, those models were run with LGM, rather than MIS3 boundary conditions. To quantify the influence of different boundary conditions on the climates of MIS3 and LGM, we perform two equilibrium climate simulations with the three-dimensional earth system model LOVECLIM, one for stadial, the other for interstadial conditions. We compare them to the LGM state simulated with the same model. Both climate states are globally 2°C warmer than LGM. A striking feature of our MIS3 simulations is the enhanced Northern Hemisphere seasonality, July being 4°C warmer than in LGM. Also, despite some modification in the location of North Atlantic deep water formation, deep water export to the South Atlantic remains unaffected. To study specifically the effect of orbital forcing, we perform two additional sensitivity experiments spun up from our stadial simulation. The insolation difference between MIS3 and LGM causes half of the 30–60°N July temperature anomaly (+6°C). In a third simulation additional freshwater forcing halts the Atlantic THC, yielding a much colder North Atlantic region (−7°C). Comparing our simulation with proxy data, we find that the MIS3 climate with collapsed THC mimics stadials over the North Atlantic better than both control experiments, which might crudely estimate interstadial climate. These results suggest that freshwater forcing is necessary to return climate from warm interstadials to cold stadials during MIS3. This changes our perspective, making the stadial climate a perturbed climate state rather than a typical, near-equilibrium MIS3 climate.
4
Van Meerbeeck, C. J., H. Renssen e D. M. Roche. "How did Marine Isotope Stage 3 and Last Glacial Maximum climates differ? – Perspectives from equilibrium simulations". Climate of the Past 5, n. 1 (5 marzo 2009): 33–51. http://dx.doi.org/10.5194/cp-5-33-2009.
Abstract (sommario):
Abstract. Dansgaard-Oeschger events occurred frequently during Marine Isotope Stage 3 (MIS3), as opposed to the following MIS2 period, which included the Last Glacial Maximum (LGM). Transient climate model simulations suggest that these abrupt warming events in Greenland and the North Atlantic region are associated with a resumption of the Thermohaline Circulation (THC) from a weak state during stadials to a relatively strong state during interstadials. However, those models were run with LGM, rather than MIS3 boundary conditions. To quantify the influence of different boundary conditions on the climates of MIS3 and LGM, we perform two equilibrium climate simulations with the three-dimensional earth system model LOVECLIM, one for stadial, the other for interstadial conditions. We compare them to the LGM state simulated with the same model. Both climate states are globally 2°C warmer than LGM. A striking feature of our MIS3 simulations is the enhanced Northern Hemisphere seasonality, July surface air temperatures being 4°C warmer than in LGM. Also, despite some modification in the location of North Atlantic deep water formation, deep water export to the South Atlantic remains unaffected. To study specifically the effect of orbital forcing, we perform two additional sensitivity experiments spun up from our stadial simulation. The insolation difference between MIS3 and LGM causes half of the 30–60° N July temperature anomaly (+6°C). In a third simulation additional freshwater forcing halts the Atlantic THC, yielding a much colder North Atlantic region (−7°C). Comparing our simulation with proxy data, we find that the MIS3 climate with collapsed THC mimics stadials over the North Atlantic better than both control experiments, which might crudely estimate interstadial climate. These results suggest that freshwater forcing is necessary to return climate from warm interstadials to cold stadials during MIS3. This changes our perspective, making the stadial climate a perturbed climate state rather than a typical, near-equilibrium MIS3 climate.
5
Ploskov, A. N., A. V. Eliseev e I. I. Mokhov. "ENSEMBLE MODELLING OF ICE SHEET DYNAMICS IN THE LAST GLACIAL CYCLE". Доклады Российской академии наук. Науки о Земле 510, n. 1 (1 maggio 2023): 99–105. http://dx.doi.org/10.31857/s2686739722602873.
Abstract (sommario):
Ensemble simulations (taking into account uncertainty of paleoclimate reconstructions) with a models for ice sheets dynamics for the last glacial cycle (last 128 kyr) are carried out. The model realistically reproduces spatial structure of major ice sheets and heights of their domes in the Northern hemisphere as well as the associated changes in global sea level. Perturbations with a sufficiently large amplitude applied to the initial paleoreconstruction result in marked differences of the modelling, in particular, durimg the Last Glacial maximu and during 58–51 kyr before present (the initial part of MIS3). According to our simualtions, the uncertainty of temperature reconstructions durng the last galcial cycle is limited to 2°C in agreement with existing estimates.
6
Zolnikov, I. D., I. C. Novikov, E. V. Deev, A. V. Panin e R. N. Kurbanov. "The Last Glaciation and Ice-Dammed Lakes in the South-East Altai". Journal "Ice and snow" 63, n. 4 (1 ottobre 2023): 639–51. http://dx.doi.org/10.31857/s207667342304018x.
Abstract (sommario):
Received June 8, 2023; revised September 4, 2023; accepted October 2, 2023The palaeogeographic scheme of the distribution of glaciers and ice-dammed lakes in the Altai during the last global glaciation (MIS-2) was compiled based on a detailed large-scale geomorphological survey. Analysis of geomorphological traces of glaciers of this time indicates that they occupied smaller areas than those of the first Late Pleistocene glaciation. By this means, the ice dams created by them were smaller that resulted in small sizes of ice-dammed lakes. The preserved levels of terraces indicate that during the first Late Pleistocene glaciation in the Kurai-Chuya depression system the ancient lake was the only one with a level of 2250 m and a total volume of 1.70 km3. During the second Late Pleistocene glaciation in the south-east Gorny Altai, another separate lake existed which was the Bartal-Kurai Lake with a level of 1700 m and a volume of 45 km3. This lake was dammed by the Mashey Glacier, which descended from the northern slopes of the North Chuaya Range. In the Chuya Depression, the existence of a landslide-dammed lake with a volume of 0.7 km3 and a level 1.750 m has been found. Its formation was not associated with glaciers of the MIS-2 stage. Direct dating of the last ice-dammed lake in the Chuya Depression with a level of 1950 m and a volume of 140 km3 has not yet been determined. This lake was dammed by the Kuehtanar Glacier, which descended from the southern slope of the Kurai ridge. The volume of ice-dammed waters of the MIS-2 time was an order of magnitude smaller than it was in the first Late Quaternary glaciation. This explains the much lower intensity of erosive and accumulative processes associated with the mega-flood occurred due to the breakthrough of the lakes during MIS-2.
7
Lian, Olav B., e Stephen R. Hicock. "Lithostratigraphy and limiting optical ages of the Pleistocene fill in Fraser River valley near Clinton, south-central British Columbia". Canadian Journal of Earth Sciences 38, n. 5 (1 maggio 2001): 839–50. http://dx.doi.org/10.1139/e00-103.
Abstract (sommario):
The Fraser River valley near Clinton contains a thick sediment fill that is presently incised down to bedrock. The sequence, approximately 500 m thick, is generally upward fining and consists of up to 100 m of glacigenic debris flow diamicton and glaciofluvialdeltaic gravel and sand at the base, overlain by about 350 m of glaciolacustrine sediments and minor diamicton, which is in turn capped by several metres of till. The sequence is interpreted to represent (i) valley aggradation in response to glaciation, followed by (ii) the impoundment of the valley by sediment and (or) ice, and the formation of a large proglacial lake(s), and finally (iii) overriding of the valley fill by glaciers. This glacial advance sequence can be readily correlated with previously studied units situated immediately to the north, most of which have been associated with the last glaciation; however, the age of these units has been based only on stratigraphic relations. We introduce limiting optical ages from a widespread glaciolacustrine unit that show that the glacial advance sequence was formed, at the earliest, during the penultimate Okanagan Centre Glaciation (oxygen isotope stage 4; ca. 7459 ka), but almost certainly during the (last) Fraser Glaciation (oxygen isotope stage 2; ca. 2412 ka). It could not have been deposited during oxygen isotope stage 6, or during an older glaciation.
8
Lehmkuhl, Frank, Michael Klinge, Henrik Rother e Daniela Hülle. "Distribution and timing of Holocene and late Pleistocene glacier fluctuations in western Mongolia". Annals of Glaciology 57, n. 71 (gennaio 2016): 169–78. http://dx.doi.org/10.3189/2016aog71a030.
Abstract (sommario):
Abstract.Despite being a key location for paleoglaciological research in north-central Asia, with the largest number of modern and Pleistocene glaciers, and in the transition zone between the humid Russian Altai and dry Gobi Altai, little is known about the precise extent and timing of Holocene and late Pleistocene glaciations in western Mongolia. Here we present detailed information on the distribution of modern and late Holocene glaciers, and new results addressing the geomorphological differentiation and numerical dating (by optically stimulated luminescence, OSL) of Pleistocene glacial sequences in these areas. For the Mongolian Altai, geochronological results suggest large ice advances correlative to marine isotope stages (MIS) 4 and 2. This is in contrast to results from the Khangai mountains, central Mongolia, showing that significant ice advances additionally occurred during MIS3. During the Pleistocene, glacial equilibrium-line altitudes (ELAs) were ~500 to >1000m lower in the more humid portion of the Russian and western Mongolian Altai, compared to 300-600 m in the drier ranges of the eastern Mongolian Altai. Pleistocene ELAs in the Khangai mountains were depressed by 700-1000 m, suggesting more humid conditions at times of major glaciation than in the eastern Mongolian Altai. This paleo-ELA pattern reveals that the precipitation gradient from the drier to the more humid regions was more pronounced during glacial times than at present.
9
Glushkova, O. Yu, e V. N. Smirnov. "Реконструкция масштабов и морфологических особенностей плейстоценовых оледенений на Северо-Востоке России". Bulletin of the North-East Science Center, n. 2 (30 giugno 2021): 50–67. http://dx.doi.org/10.34078/1814-0998-2021-2-50-67.
Abstract (sommario):
Based on the currently available data, it has been established that the earliest glaciations occurred in the Late Eopleistocene and at the end of the Early Neopleistocene. They had local distribution in the most uplifted parts of the Chersky Range. Their traces are presented in the form of moraines enclosed in sediments of intermontain depressions. Glacial forms of this age have not been identified in the relief of mountains and plains in the North-East of Russia. The Middle Neopleistocene glaciation was the largest, both in area and length of individual glaciers. It was mountain-valley and reticulated; in some areas, mountain-cover. Its time coincides with the stage of activation of the ascending neotectonic movements in the Middle Neopleistocene. Traces of the last two Late Neopleistocene glaciations are well expressed in the relief in widespread exaration, moraine, and fluvioglacial complexes. The first Late Neopleistocene glaciation (Zyryan) was significantly inferior to the one occurred in the Middle Neopleistocene, in all parameters, but it also left large amphitheaters of terminal moraines in the foothill belts. Glacial complexes of the last Late Neopleistocene glaciation are widespread in areas 2-3 times smaller than the previous one and, as a rule, are located within its contours.
10
Shulmeister, James, Glenn D. Thackray, Tammy M. Rittenour e Olivia M. Hyatt. "Multiple glacial advances in the Rangitata Valley, South Island, New Zealand, imply roles for Southern Hemisphere westerlies and summer insolation in MIS 3 glacial advances". Quaternary Research 89, n. 2 (22 febbraio 2018): 375–93. http://dx.doi.org/10.1017/qua.2017.108.
Abstract (sommario):
AbstractStratigraphic evidence and extensive optically stimulated luminescence (OSL) geochronology from an 18-km-long reach of the middle Rangitata Valley, South Island, New Zealand, provide evidence for at least six distinct glacial advances during the last glacial cycle. These include four well-constrained Marine Oxygen Isotope Stage (MIS) 3 and 2 advances at ca. 38 ka, ca. 27 ka, ca. 21 ka and at 18 ka, as well as less well-constrained advances in MIS 4 and/or early MIS 3. Ice occupied a farther downvalley reach of the Rangitata from 38 ka to after 18 ka, indicating that near-full glacial conditions persisted for most of the last 20 ka of the last glaciation, though the glacier still fluctuated significantly, as reflected by the numerous distinguishable advances. Global or regional cooling alone cannot explain the persistence of near-maximum glacial conditions for this extended period, nor can it explain the occurrence of the largest advances ca. 32 ka. Instead, we invoke the northward expansion of the westerlies during MIS 3 as the cause for the early widespread glaciation, wherein enhanced westerly flow under moderate cooling maximised glacial extents. Local insolation favoured extended MIS 3 glaciation until ca. 32 ka. Increasing summer insolation gradually reduced glacial extents after ca. 28 ka.
11
Mikharevich, M. V., e S. G. Prudnikov. "RESULTS OF PALYNOLOGICAL AND PALEOCARPOLOGICAL ANALYSES OF THE LATE NEOPLEISTOCENE INTERGLACIAL AND PERIGLACIAL DEPOSITS (EAST TYVA HIGHLANDS, SERLIGKHEM INTERMOUNTAIN BASIN)". Geology and mineral resources of Siberia, n. 2 (2023): 3–9. http://dx.doi.org/10.20403/2078-0575-2023-2-3-9.
Abstract (sommario):
The last Late Pleistocene glaciation deposits of the tongue-like basin, as well as an interglacial alluvium overlapped by glaciofluvial have been studied on the basis of application of palynological and paleocarpological methods of analysis in the basin of the middle course of the Yenisei River. The tongue-like basin deposits were compared with those previously studied by researchers in headwaters of the Kharal River (Azas glacial complex), formed according to OSL dates in the interval of the end of MIS-3–MIS-2. Fluvioglacial overlapping an interglacial alluvium is compared with the same glacial complex. A rather large scattering of absolute dates, some of which fall within the last Neopleistocene thermochron, palynological and paleocarpological complexes from glacial deposits characterizing the stage of glaciation degradation, raise the question of independence of the second Late Neopleistocene one. Further geochronological study of the interglacial alluvium section is proposed to clarify the lower time boundary of the Azas shield glacier.
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Lindner, Leszek, e Jan Dzierżek. "Pleistocene deposits in the western part of the Holy Cross Mountains". Studia Quaternaria 36, n. 2 (2019): 75–85. http://dx.doi.org/10.24425/sq.2019.126381.
Abstract (sommario):
The paper presents characteristics of the Pleistocene sediments in the western part of the Holy Cross Mountains. They are subdivided into four complexes and their stratigraphic setting is referred to the updated scheme for the Pleistocene of Poland. The Preglacial Complex includes fluvial sediments characteristic for its lack of Scandinavian material. Sediments of three main glaciations (Nidanian, Sanian 1 and Sanian 2) within the South Polish Complex, are referred also as the South Polish Glaciations. The oldest of these glaciations (Nidanian) is separated from the middle glaciation (Sanian 1) by sediments of the Podlasian Interglacial, represented by clay at the Kozi Grzbiet Cave that contains faunal remains and record of the Brunhes/Matuyama palaeomagnetic boundary. During the middle (Sanian 1) and youngest glaciation (Sanian 2), the Holy Cross Mountains were almost completely covered by the Scandinavian ice sheet, forming glacial deposits separated by fluvial series of the Ferdynandovian Interglacial. The Middle Polish Complex begins with sediments of the Mazovian Interglacial, represented by a pollen record from the Zakrucze site. They are followed by deposits of periglacial and fluvial origin of the Liwiecian Glaciation, Zbójnian Interglacial, Krznanian Glaciation and Lublinian Interglacial. The following glaciation (Odranian) is represented by the youngest glacial deposits that document presence of the Scandinavian ice-sheet in the westernmost part of the Holy Cross Mountains. The North Polish Complex is composed of a climatic warming (Eemian Interglacial) and cooling (Vistulian Glaciation), and is represented by valley and periglacial deposits. The last cooling of the Pleistocene is recorded in faunal remains in the Raj Cave.
13
Pesjak, Lea, Andrew McMinn, Zanna Chase e Helen Bostock. "Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability". Climate of the Past 19, n. 2 (14 febbraio 2023): 419–37. http://dx.doi.org/10.5194/cp-19-419-2023.
Abstract (sommario):
Abstract. Although diatoms can provide important palaeoenvironmental information about seasonal sea ice extent productivity, sea surface temperature, and ocean circulation variability, there are still relatively few studies analysing the last glacial cycle near the Antarctic continent. This study examines diatom assemblages over the last glacial cycle from core TAN1302-44, offshore Adélie Land, East Antarctica. Two distinct diatom assemblages were identified using principal component analysis (PC 1–PC 2). The PC 1 assemblage is characterised by Thalassiosira lentiginosa, Actinocyclus actinochilus, Eucampia antarctica, Azpeitia tabularis and Asteromphalus hyalinus and is associated with the interglacial, sedimentary Facies 1, suggesting that the MIS 5e and Holocene interglacials were characterised by seasonal sea ice environments with similar ocean temperature and circulation. The PC 2 assemblage is characterised by Fragilariopsis obliquecostata, Asteromphalus parvulus and Thalassiosira tumida and is associated with the glacial Facies 2. The variability of PC 2 indicates that, during the MIS 4–2 glacial and the last glaciation, there was an increase in the length of the sea ice season compared with that of the interglacial period, yet there was still no permanent sea ice cover. The initial increase of PC 2 at the start of the glaciation stage and then the gradual increase throughout late MIS 4–2 suggest that sea ice cover steadily increased, reaching a maximum towards the end of MIS 2. The increase in sea ice during glaciation and MIS 4–2 glacial is further supported by the increase in the Eucampia index (terminal/intercalary valve ratio), an additional proxy for sea ice, which coincides with increases in PC 2. Aside from the statistical results, the increase in the relative abundance of Thalassiothrix antarctica at 40 and 270 cm suggests that, during the last two deglacials, there was a period of enhanced nutrient delivery, which is inferred to reflect an increase in upwelling of Circumpolar Deep Water. Interestingly, the diatom data suggest that, during the last deglacial, the onset of increased Circumpolar Deep Water occurred after the loss of a prolonged sea ice season (decrease in PC 2) but before the ice sheet started to retreat (increase in IRD). Together, these results suggest the changes in sea ice season potentially influenced the ocean's thermohaline circulation and were important factors in driving the climate transitions. The results contribute to our understanding of the sea ice extent and ocean circulation changes proximal to East Antarctica over the last glacial cycle.
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Aber, James S., e Jan Lundqvist. "Glaciotectonic Structures in Central Sweden and their Significance for Glacial Theory". Géographie physique et Quaternaire 42, n. 3 (18 dicembre 2007): 315–23. http://dx.doi.org/10.7202/032739ar.
Abstract (sommario):
ABSTRACT Various glaciotectonic structures and landforms created by ice pushing are common in drift and interstadial sediments in a narrow belt of central Sweden. Described examples from the Lake Storsjôn vicinity demonstrate that glaciotectonic deformation took place while the area was deeply covered by the last Fennoscandian Ice Sheet. Deformation was controlled by pressure gradients related to position of the ice divide and ice movement away from the divide. As the position of the divide shifted during the last glaciation, so did the orientation of glaciotectonic structures. The regional distribution of glaciotectonic features in Fennoscandia falls into three zones: (1) inner zone of widespread, small- to moderate-sized features in older drift, (2) intermediate zone of small, isolated features in drift of the last glaciation, and (3) outer zone with all manner of large and small features in drift and soft bedrock. These zones are the cumulative results of multiple glaciations and reflect the overall distribution of deformable sediment and bedrock within the continental substratum.
15
Hicock, Stephen R., e Olav B. Lian. "The Sisters Creek Formation: Pleistocene sediments representing a nonglacial interval in southwestern British Columbia at about 18 ka". Canadian Journal of Earth Sciences 32, n. 6 (1 giugno 1995): 758–67. http://dx.doi.org/10.1139/e95-065.
Abstract (sommario):
Sisters Creek Formation is formally defined, stratotypes are established for it, and the time–space chart is updated for the Fraser Lowland, southwestern British Columbia. The Sisters Creek is a Pleistocene formation comprising in situ and reworked organic-rich sediments, and nonorganic silt, sand, and gravel. The formation was deposited during the Port Moody interstade (within the Late Wisconsinan Fraser Glaciation; δ18O stage 2) between the Coquitlam stade (early Fraser Glaciation) and the main Vashon stadial maximum that occurred about 14.5 ka. The Sisters Creek Formation represents a glacial recession in southwestern British Columbia that generally coincided with the timing of the last global glacial maximum. The new time–space chart implies that, in Fraser Lowland, the Fraser Glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains, which remained ice-covered during interstades.
16
Siegert, Martin J. "Quantitative reconstructions of the last glaciation of the Barents Sea: a review of ice-sheet modelling problems". Progress in Physical Geography: Earth and Environment 21, n. 2 (giugno 1997): 200–229. http://dx.doi.org/10.1177/030913339702100202.
Abstract (sommario):
Reconstructions of the Late Weichselian ice sheet within the Barents Sea have varied from complete coverage of a large (3 km thick) grounded ice mass, to a situation in which glacier extent was restricted to the Svalbard coast. Recently obtained geological data indicate that 1) glaciation of the Barents Sea occurred after 25 000 years ago; 2) the ice sheet was at its maximum extent at around 20 000 years ago; 3) the maximum-sized ice sheet covered the entire Barents Shelf; and 4) ice-sheet decay began at about 16 500 years ago. The ice sheet was, consequently, one of the last to grow and first to decay during the last glacial. However, this recently derived chronology of glacial events has reintroduced problems concerning the thickness distribution of the maximum- sized ice sheet, and the glaciological processes by which rapid glaciation and ice decay happened. In particular, the situation in which regional glaciation of Bjomoya occurred at the same time as grounded ice (and ice-stream activity) within the relatively deep Bjørnøyrenna is yet to be understood fully. This article provides a review of reconstructions of the last Barents ice mass, and compares these models with geological and palaeoceanographic information from the area in order to provide a summary of what is presently known, and to indicate explicitly what is not known, about the Late Weichselian Barents Sea ice sheet.
17
Gschwentner, Philipp, Hanns Kerschner e Christoph Spötl. "Late Glacial ice advance in the Kellerjoch region near Schwaz (Tyrol, Eastern Alps)". Austrian Journal of Earth Sciences 113, n. 1-2 (1 giugno 2020): 211–27. http://dx.doi.org/10.17738/ajes.2020.0013.
Abstract (sommario):
Abstract The Kellerjoch forms a small isolated massif at the northernmost rim of the central Eastern Alps of Tyrol and shows a number of geomorphological features of glacial and periglacial origin. Mapping yields evidence of two local glaciations postdating the Last Glacial Maximum. Using a simple glaciological approach the palaeoglaciers related to these events were reconstructed. The older glaciation yields an equilibrium line altitude (ELA) ranging from 1660 m for the maximum extent to 1800 m a.s.l. for the innermost moraine. For the younger glaciation, ELAs were reconstructed at 1905 m and 1980 m (depending on the reconstruction) for the Kellerjoch palaeoglacier 2, as well as 1870 m and 2060 m a.s.l. for the Proxen palaeoglacier and the Gart palaeoglacier, respectively. A comparison with published data from the Eastern Alps shows that the older glaciation in the Kellerjoch region likely corresponds to the Gschnitz stadial. Low basal shear stresses of the glacier tongues point towards a cold and dry climate, similar to the reconstruction for the Gschnitz type locality at Trins. The younger glaciation cannot unambiguously be assigned to a specific Late Glacial ice advance, but a Younger Dryas age is a distinct possibility.
18
Kaplan, Michael R., Daniel C. Douglass, Bradley S. Singer, Robert P. Ackert e Marc W. Caffee. "Cosmogenic nuclide chronology of pre-last glacial maximum moraines at Lago Buenos Aires, 46�S, Argentina". Quaternary Research 63, n. 3 (maggio 2005): 301–15. http://dx.doi.org/10.1016/j.yqres.2004.12.003.
Abstract (sommario):
At Lago Buenos Aires, Argentina, 10Be, 26Al, and 40Ar/39Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000�16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/103 yr, both yield a common estimate age of 150,000�140,000 yr for the two moraines. The erosion rate estimate derives from 10Be and 26Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded 40Ar/39Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.
19
Sturchio, Neil C., Kenneth L. Pierce, Michael T. Murrell e Michael L. Sorey. "Uranium-Series Ages of Travertines and Timing of the Last Glaciation in the Northern Yellowstone Area, Wyoming-Montana". Quaternary Research 41, n. 3 (maggio 1994): 265–77. http://dx.doi.org/10.1006/qres.1994.1030.
Abstract (sommario):
AbstractUranium-series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation (Pinedale) in the northern Yellowstone area. Dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation. We determine the following chronology of the Pinedale Glaciation, with the key assumption that travertine deposits (and associated carbonate veins) perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits: (1) the early Pinedale outlet glacier advanced well downvalley between 47,000 and 34,000 yr B.P.; (2) the outlet glacier receded to an interstadial position between 34,000 and 30,000 yr B.P.; (3) an extensive Pinedale ice advance occurred between 30,000 and 22,500 yr B.P.; (4) a major recession occurred between 22,500 and 19,500 yr B.P.; (5) a minor readvance (Deckard Flats) culminated after 19,500 yr B.P.; and (6) recession from the Deckard Flats position was completed before 15,500 yr B.P. This chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high-resolution ice-core records from the Greenland ice sheet.
20
Saini, Himadri, Katrin J. Meissner, Laurie Menviel e Karin Kvale. "Impact of iron fertilisation on atmospheric CO2 during the last glaciation". Climate of the Past 19, n. 7 (28 luglio 2023): 1559–84. http://dx.doi.org/10.5194/cp-19-1559-2023.
Abstract (sommario):
Abstract. While several processes have been identified to explain the decrease in atmospheric CO2 during glaciations, a better quantification of the contribution of each of these processes is needed. For example, enhanced aeolian iron input into the ocean during glacial times has been suggested to drive a 5 to 28 ppm atmospheric CO2 decrease. Here, we constrain this contribution by performing a set of sensitivity experiments with different aeolian iron input patterns and iron solubility factors under boundary conditions corresponding to 70 000 years before present (70 ka), a time period characterised by the first observed peak in glacial dust flux. We show that the decrease in CO2 as a function of Southern Ocean iron input follows an exponential decay relationship. This exponential decay response arises due to the saturation of the biological pump efficiency and levels out at ∼21 ppm in our simulations. We show that the changes in atmospheric CO2 are more sensitive to the solubility of iron in the ocean than the regional distribution of the iron fluxes. If surface water iron solubility is considered constant through time, we find a CO2 drawdown of ∼4 to ∼8 ppm. However, there is evidence that iron solubility was higher during glacial times. A best estimate of solubility changing from 1 % during interglacials to 3 % to 5 % under glacial conditions yields a ∼9 to 11 ppm CO2 decrease at 70 ka, while a plausible range of CO2 drawdown between 4 to 16 ppm is obtained using the wider but possible range of 1 % to 10 %. This would account for ∼12 %–50 % of the reconstructed decrease in atmospheric CO2 (∼32 ppm) between 71 and 64 ka. We further find that in our simulations the decrease in atmospheric CO2 concentration is solely driven by iron fluxes south of the Antarctic polar front, while iron fertilisation elsewhere plays a negligible role.
21
Thackray, Glenn D. "Extensive Early and Middle Wisconsin Glaciation on the Western Olympic Peninsula, Washington, and the Variability of Pacific Moisture Delivery to the Northwestern United States". Quaternary Research 55, n. 3 (maggio 2001): 257–70. http://dx.doi.org/10.1006/qres.2001.2220.
Abstract (sommario):
AbstractLarge glaciers descended western valleys of the Olympic Mountains six times during the last (Wisconsin) glaciation, terminating in the Pacific coastal lowlands. The glaciers constructed extensive landforms and thick stratigraphic sequences, which commonly contain wood and other organic detritus. The organic material, coupled with stratigraphic data, provides a detailed radiocarbon chronology of late Pleistocene ice-margin fluctuations. The early Wisconsin Lyman Rapids advance, which terminated prior to ca. 54,000 14C yr B.P., represented the most extensive ice cover. Subsequent glacier expansions included the Hoh Oxbow 1 advance, which commenced between ca. 42,000 and 35,000 14C yr B.P.; the Hoh Oxbow 2 advance, ca. 30,800 to 26,300 14C yr B.P.; the Hoh Oxbow 3 advance, ca. 22,000–19,300 14C yr B.P.; the Twin Creeks 1 advance, 19,100–18,300 14C yr B.P.; and the subsequent, undated Twin Creeks 2 advance. The Hoh Oxbow 2 advance represents the greatest ice extent of the last 50,000 yr, with the glacier extending 22 km further downvalley than during the Twin Creeks 1 advance, which is correlative with the global last glacial maximum. Local pollen data indicate intensified summer cooling during successive stadial events. Because ice extent was diminished during colder stadial events, precipitation—not summer temperature—influenced the magnitude of glaciation most strongly. Regional aridity, independently documented by extensive pollen evidence, limited ice extent during the last glacial maximum. The timing of glacier advances suggests causal links with North Atlantic Bond cycles and Heinrich events.
22
Delmas, Magali, Yanni Gunnell, Régis Braucher, Marc Calvet e Didier Bourlès. "Exposure age chronology of the last glaciation in the eastern Pyrenees". Quaternary Research 69, n. 2 (marzo 2008): 231–41. http://dx.doi.org/10.1016/j.yqres.2007.11.004.
Abstract (sommario):
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.
23
Rother, Henrik, Frank Lehmkuhl, David Fink e Veit Nottebaum. "Surface exposure dating reveals MIS-3 glacial maximum in the Khangai Mountains of Mongolia". Quaternary Research 82, n. 2 (settembre 2014): 297–308. http://dx.doi.org/10.1016/j.yqres.2014.04.006.
Abstract (sommario):
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.
24
Seguinot, Julien, Susan Ivy-Ochs, Guillaume Jouvet, Matthias Huss, Martin Funk e Frank Preusser. "Modelling last glacial cycle ice dynamics in the Alps". Cryosphere 12, n. 10 (10 ottobre 2018): 3265–85. http://dx.doi.org/10.5194/tc-12-3265-2018.
Abstract (sommario):
Abstract. The European Alps, the cradle of pioneering glacial studies, are one of the regions where geological markers of past glaciations are most abundant and well-studied. Such conditions make the region ideal for testing numerical glacier models based on simplified ice flow physics against field-based reconstructions and vice versa. Here, we use the Parallel Ice Sheet Model (PISM) to model the entire last glacial cycle (120–0 ka) in the Alps, using horizontal resolutions of 2 and 1 km. Climate forcing is derived using two sources: present-day climate data from WorldClim and the ERA-Interim reanalysis; time-dependent temperature offsets from multiple palaeo-climate proxies. Among the latter, only the European Project for Ice Coring in Antarctica (EPICA) ice core record yields glaciation during marine oxygen isotope stages 4 (69–62 ka) and 2 (34–18 ka). This is spatially and temporally consistent with the geological reconstructions, while the other records used result in excessive early glacial cycle ice cover and a late Last Glacial Maximum. Despite the low variability of this Antarctic-based climate forcing, our simulation depicts a highly dynamic ice sheet, showing that Alpine glaciers may have advanced many times over the foreland during the last glacial cycle. Ice flow patterns during peak glaciation are largely governed by subglacial topography but include occasional transfluences through the mountain passes. Modelled maximum ice surface is on average 861 m higher than observed trimline elevations in the upper Rhône Valley, yet our simulation predicts little erosion at high elevation due to cold-based ice. Finally, despite the uniform climate forcing, differencesin glacier catchment hypsometry produce a time-transgressive Last Glacial Maximum advance, with some glaciers reaching their modelled maximum extent as early as 27 ka and others as late as 21 ka.
25
DOTSENKO, Valeriy, e Ibragim KERIMOV. "ABOUT THE REASONS OF CLIMATE WARMING BASED ON STUDYING THE HISTORY OF QUATERNARY GLACIOSES OF THE CAUCASUS (ON THE EXAMPLE OF THE INTERDURCHIE TEREK AND THE ANDIAN KOISU)". Sustainable Development of Mountain Territories 12, n. 3 (30 settembre 2020): 461–71. http://dx.doi.org/10.21177/1998-4502-2020-12-3-461-471.
Abstract (sommario):
The Greater Caucasus experienced repeated glaciation during the Quaternary (early, middle, upper Pleistocene, late Glacial, and late Holocene), which occurred under changing climatic conditions and differentiated tectonic movements. These glaciations, of course, are associated with changes in terrain, the formation of new deposits, transgressions and regressions of the Caspian Sea, changes in vegetation and soil types, so the problem of glaciation affects all earth Sciences to varying degrees. The study of Quaternary glaciation, especially Holocene glaciation, is currently relevant for understanding climate change. Against the background of significant climate fluctuations within the epochs of glaciation, there are smaller cooling phases that cause the temporary onset of glaciers. Short-term climate fluctuations are manifested in oscillations – minor fluctuations in the languages of glaciers. All this indicates that the climate undergoes significant changes in a short time, which are reflected in the morphosculpture of the terrain, the latest deposits and modern precipitation. Glaciation of the Greater Caucasus in the Prikazbeksky region reached its maximum in the middle Pleistocene,when glaciers went far into the Ossetian basin. All these traces have been preserved due to the lower capacity of the Chanty-Argun glacier and its fluvioglacial flow, which developed during the late Pleistocene epoch. Volcanic activity, especially active in the late Pliocene and continuing up to the present time, is associated with the late horn stage of development of the Caucasus. The formation of the Rukhs-Dzuar molass formation more than 2 km thick in the late Pleistocene in the Ossetian basin of the Tersky-Caspian flexure is associated with the activity of volcanoes in the Kazbek volcanic region. In the early Pleistocene, volcanic activity on the BC decreased significantly. The most intense outbreak of volcanism in the Kazbek and Elbrus volcanic regions occurred at the beginning of the late Pleistocene, which roughly coincided with the maximum phase of the late Pleistocene (Bezengian) glaciation. Then, in the second half of the late Pleistocene, volcanic activity was manifested on the mount Kazbek. The last outbreak of volcanic activity occurred in the Holocene no more than 2-3 thousand years ago. Fresh lavas are available on Elbrus, Kazbek, in the Terek valley near villages. Sioni and on the Kel volcanic plateau. Fumarolic activity still continues on Elbrus. Thus, in the Kazbek region, eruptions occurred from the late Pliocene to the late Holocene inclusive. Keywords: Pleistocene, Holocene, glaciation stages, nival-glacial processes, causes of glaciations, climate change, anthropogenic factors, natural factors, Earth degassing, magmatogenic degassing branch, seismotectonic degassing branch, greenhouse gases, newest geodynamics, volcanism, mud regimes, volcanism, methane hydrates, land degradation, water reclamation.
26
Brookes, Ian A. "Ice Marks in Newfoundland: A History of Ideas". Géographie physique et Quaternaire 36, n. 1-2 (29 novembre 2007): 139–63. http://dx.doi.org/10.7202/032474ar.
Abstract (sommario):
ABSTRACT This essay traces the evolution of ideas on the origin of features in Newfoundland now ascribed to glaciation, through the period 1822-1981. It identifies "Pre-cognitive," "Drift," and "Glacial" phases, with the last phase divided into seven sub-phases. In the Glacial Phase, debate centred on 1) the relative roles of Labrador ice and ice from the island of Newfoundland, 2) the areal and vertical extent of ice masses, and 3) the number and chronology of glacial episodes. Alexander Murray is credited with first recognizing glaciation in Newfoundland in 1866, and the background to his perspicacity is discussed. The evolution of ideas from the late-nineteenth century to the present is related to improving access, exploration by increasingly widely experienced scientists, the import of concepts from outside the region, the development of chronological tools, and improvements in glaciological theory.
27
Roman, Małgorzata, Danuta Dzieduszyńska e Joanna Petera-Zganiacz. "Łódź Region and its Northern Vicinity under Vistulian Glaciation Conditions". Quaestiones Geographicae 33, n. 3 (1 settembre 2014): 155–63. http://dx.doi.org/10.2478/quageo-2014-0038.
Abstract (sommario):
Abstract An overview of palaeogeographical findings of the last glacial period (MIS 5d-MIS 2) has been given for the Łódź region. Processes which influenced the area outside of ice-sheet margin are presented with respect to space and time, as predominantly driven by different types of periglacial environment. Attention was paid to leading accumulative and erosional processes and resulting landforms, still well-pronounced in the landscape. Recently, the picture of the area discussed, during the Vistulian was completed and identified was the mechanism of the LGM ice-sheet advance onto the Płock lobe. Borderline location of the Łódź region offers comprehensive research on the time and processes and determines its significance on the geomorphological map of Poland.
28
Marchetti, David W., M. Scott Harris, Christopher M. Bailey, Thure E. Cerling e Sarah Bergman. "Timing of glaciation and last glacial maximum paleoclimate estimates from the Fish Lake Plateau, Utah". Quaternary Research 75, n. 1 (gennaio 2011): 183–95. http://dx.doi.org/10.1016/j.yqres.2010.09.009.
Abstract (sommario):
AbstractThe High Plateaus of Utah include seven separate mountain ranges that supported glaciers during the Pleistocene. The Fish Lake Plateau, located on the eastern edge of the High Plateaus, preserves evidence of at least two glacial advances. Four cosmogenic 3He exposure ages of boulders in an older moraine range from 79 to 159 ka with a mean age of 129 ± 39 ka and oldest ages of 152 ± 3 and 159 ± 5 ka. These ages suggest deposition during the type Bull Lake glaciation and Marine Oxygen Isotope Stage (MIS) 6. Twenty boulder exposure ages from four different younger moraines indicate a local last glacial maximum (LGM) of ~ 21.1 ka, coincident with the type Pinedale glaciation and MIS 2. Reconstructed Pinedale-age glaciers from the Fish Lake Plateau have equilibrium-line altitudes ranging from 2950 to 3190 m. LGM summer temperature depressions for the Fish Lake Plateau range from −10.7 to −8.2°C, assuming no change in precipitation. Comparison of the Fish Lake summer temperature depressions to a regional dataset suggests that the Fish Lake Plateau may have had a slight increase (~ 1.5× modern) in precipitation during the LGM. A series of submerged ridges in Fish Lake were identified during a bathymetric survey and are likely Bull Lake age moraines.
29
Zichu, Xik. "Ice Formation and Ice Structure on Law Dome, Antarctica". Annals of Glaciology 6 (1985): 150–53. http://dx.doi.org/10.3189/1985aog6-1-150-153.
Abstract (sommario):
Snow stratigraphical studies, together with crystallographic and oxygen isotope analyses, have affirmed the existence of a complete range of ice formation zones on the Law Dome, Antarctica. Asymmetric distribution of these zones and changes in the types of ice formation with depth in snow pits dug near the boundaries of the zones show an asymmetry in accumulation and thermal conditions in different sites on Law Dome, and a climatic change in past years. Crystallographic studies of ice from two boreholes near Cape Forger (BHC i and BHC 2) show change of microtexture and fabric of the ice crystals with depth. Six different layers of ice can be identified: 1) a deposition layer with polygonal shaped crystals, an ice fabric which is dependent on the ice formation process; 2) a transition layer with porphyrblastic crystals and a girdle fabric pattern developing toward a two-pole fabric; 3) a fine grained layer with cataclastic crystals and strong, nearly vertical single pole c-axis fabric; 4) a coarse grained layer with large, interlocking, branched crystals and a diamond pattern of fabric; 5) a second fine grained layer with single maximum fabric; 6) a second coarse grained layer with multi-maxima fabric. The origin of the second fine grained layer, found in the ice of the last glaciation is discussed. The author suggests that this ice results from conditions during the last glaciation.
30
Zichu, Xik. "Ice Formation and Ice Structure on Law Dome, Antarctica". Annals of Glaciology 6 (1985): 150–53. http://dx.doi.org/10.1017/s0260305500010211.
Abstract (sommario):
Snow stratigraphical studies, together with crystallographic and oxygen isotope analyses, have affirmed the existence of a complete range of ice formation zones on the Law Dome, Antarctica. Asymmetric distribution of these zones and changes in the types of ice formation with depth in snow pits dug near the boundaries of the zones show an asymmetry in accumulation and thermal conditions in different sites on Law Dome, and a climatic change in past years. Crystallographic studies of ice from two boreholes near Cape Forger (BHC i and BHC 2) show change of microtexture and fabric of the ice crystals with depth. Six different layers of ice can be identified: 1) a deposition layer with polygonal shaped crystals, an ice fabric which is dependent on the ice formation process; 2) a transition layer with porphyrblastic crystals and a girdle fabric pattern developing toward a two-pole fabric; 3) a fine grained layer with cataclastic crystals and strong, nearly vertical single pole c-axis fabric; 4) a coarse grained layer with large, interlocking, branched crystals and a diamond pattern of fabric; 5) a second fine grained layer with single maximum fabric; 6) a second coarse grained layer with multi-maxima fabric. The origin of the second fine grained layer, found in the ice of the last glaciation is discussed. The author suggests that this ice results from conditions during the last glaciation.
31
Foster, G. L., D. J. Lunt e R. R. Parrish. "Mountain uplift and the glaciation of North America – a sensitivity study". Climate of the Past 6, n. 5 (25 ottobre 2010): 707–17. http://dx.doi.org/10.5194/cp-6-707-2010.
Abstract (sommario):
Abstract. The Miocene (~24 to ~5 million years ago) was a period of relative global warmth compared to the Quaternary (~2 million years ago to present; e.g. Zachos et al., 2001) and was characterised by the intermittent glaciation of Antarctica only. Paradoxically, the majority of available proxy data suggest that during the Miocene, pCO2 was similar, or even lower, than the pre-industrial levels (280 ppmv; Pagani et al., 1999; Pearson and Palmer, 2000; Kürschner et al., 1996, 2008) and at times probably crossed the modelled threshold value required for sustained glaciation in the Northern Hemisphere (DeConto et al., 2008). Records of ice rafted debris and the oxygen isotope composition of benthic foraminifera suggest that at several times over the last 25 million years substantial amounts of continental ice did build up in the Northern Hemisphere but none of these led to prolonged glaciation. In this contribution, we review evidence that suggests that in the Miocene the North American Cordillera was, at least in parts, considerably lower than today. We present new GCM simulations that imply that small amounts of uplift of the North American Cordillera result in significant cooling of the northern North American Continent. Offline ice sheet modelling, driven by these GCM outputs, suggests that with a reduced topography, inception of the Cordilleran ice sheet is prohibited. This suggests that uplift of the North American Cordillera in the Late Miocene may have played an important role in priming the climate for the intensification of Northern Hemisphere glaciation in the Late Pliocene.
32
Pochocka-Szwarc, Katarzyna. "Some aspects of the last glaciation in the Mazury Lake District (north-eastern Poland)". Acta Palaeobotanica 53, n. 1 (1 giugno 2013): 3–8. http://dx.doi.org/10.2478/acpa-2013-0001.
Abstract (sommario):
ABSTRACT The morphology of the Mazury Lake District (north-eastern Poland) dates from 24-19 ka (main stadial of the youngest Vistulian glaciation). During this last glacial maximum (MIS 2) a belt with lacustrine basins was formed when the ice sheet retreated at the end of the Pomeranian phase. The ice-sheet retreat is morphologically also expressed by the occurrence of end moraines. The study area is situated in the Skaliska Basin, in the northern part of the Lake District (near the Polish/ Russian border), at the periphery of zone with end moraines. Originally the basin was an ice-dammed depression filled with melt water; the water flowed out into the developing Pregoła valley when the ice retreated and did no longer dam off the depression. The basin, which is surrounded by hill-shaped moraines, is filled now with Late Glacial and Holocene glaciolacustrine sediments. The organic sediments of the basin record the history of the Late Glacial and Holocene climatic changes in this region.
33
HEUSSER, C., e L. HEUSSER. "Submillennial palynology and palaeoecology of the last glaciation at Taiquemó (∼50,000calyr, MIS 2–4) in southern Chile". Quaternary Science Reviews 25, n. 5-6 (marzo 2006): 446–54. http://dx.doi.org/10.1016/j.quascirev.2005.04.008.
34
Heaton, T. H. E., A. S. Talma e J. C. Vogel. "Dissolved Gas Paleotemperatures and 18O Variations Derived from Groundwater Near Uitenhage, South Africa". Quaternary Research 25, n. 1 (gennaio 1986): 79–88. http://dx.doi.org/10.1016/0033-5894(86)90045-1.
Abstract (sommario):
Under the near-ideal hydrologic conditions provided by the Uitenhage artesian aquifer, reliable estimates of paleotemperatures were obtained by measurement of the dissolved N2 and Ar in groundwater, confidently dated in the range 28,000 yr B.P. to the present using 14C. The mean annual air temperature in this area during the last glaciation is calculated to have been, on average, 1/2°C lower than during the Holocene. The change in the 18O/16O ratio of the groundwater, corrected for changes in ocean water, amounted to 0.4‰ per °C.
35
Brauer, Achim, Markus J. Schwab, Brian Brademann, Sylvia Pinkerneil e Martin Theuerkauf. "Tiefer See – a key site for lake sediment research in NE Germany". DEUQUA Special Publications 2 (15 agosto 2019): 89–93. http://dx.doi.org/10.5194/deuquasp-2-89-2019.
Abstract (sommario):
Abstract. Tiefer See formed in a subglacial gully system at the end of the last glaciation in the northeast German lowlands. The lake has been selected as a focus site within the TERENO (Terrestrial Environmental Observatory) NE German observatory because it forms annual laminations (calcite varves) providing detailed information of past climate and environmental changes. Our research integrates palaeolimnology and limnology by combining high-resolution analyses of the sediment record with a comprehensive monitoring of the lake and its sedimentation processes since 2012. This allows evaluation of the observed effects of ongoing climate change in the context of the long-term history of the lake. The lacustrine sediment profile comprises the last 13 000 years and is dated by a multiple dating approach. The sedimentation is dominated by biochemical calcite formation and algal blooms. Detrital material from the catchment forms only a minor component even during times of increased human impact. Repeated changes between well-varved, poorly varved and homogeneous sediment intervals indicate that sedimentation processes in the lake are particularly sensitive to changes in lake circulation. The research at Tiefer See is embedded in ICLEA (https://www.iclea.de, last access: 2 August 2019) and BaltRap (https://www.io-warnemuende.de/projekt/167/baltrap.html, last access: 2 August 2019) projects.
36
Nisbet, Euan G., e R. Ellen R. Nisbet. "Methane, oxygen, photosynthesis, rubisco and the regulation of the air through time". Philosophical Transactions of the Royal Society B: Biological Sciences 363, n. 1504 (16 maggio 2008): 2745–54. http://dx.doi.org/10.1098/rstb.2008.0057.
Abstract (sommario):
Rubisco I's specificity, which today may be almost perfectly tuned to the task of cultivating the global garden, controlled the balance of carbon gases and O 2 in the Precambrian ocean and hence, by equilibration, in the air. Control of CO 2 and O 2 by rubisco I, coupled with CH 4 from methanogens, has for the past 2.9 Ga directed the global greenhouse warming, which maintains liquid oceans and sustains microbial ecology. Both rubisco compensation controls and the danger of greenhouse runaway (e.g. glaciation) put limits on biological productivity. Rubisco may sustain the air in either of two permissible stable states: either an anoxic system with greenhouse warming supported by both high methane mixing ratios as well as carbon dioxide, or an oxygen-rich system in which CO 2 largely fulfils the role of managing greenhouse gas, and in which methane is necessarily only a trace greenhouse gas, as is N 2 O. Transition from the anoxic to the oxic state risks glaciation. CO 2 build-up during a global snowball may be an essential precursor to a CO 2 -dominated greenhouse with high levels of atmospheric O 2 . Photosynthetic and greenhouse-controlling competitions between marine algae, cyanobacteria, and terrestrial C3 and C4 plants may collectively set the CO 2 : O 2 ratio of the modern atmosphere (last few million years ago in a mainly glacial epoch), maximizing the productivity close to rubisco compensation and glacial limits.
37
Vikulina, Marina, Mihail Zimin e Fedor Romanenko. "Assessment of the size of very small glaciers in Khibiny mountains". InterCarto. InterGIS 27, n. 1 (2021): 409–17. http://dx.doi.org/10.35595/2414-9179-2021-1-27-409-417.
Abstract (sommario):
The presence of very small glaciation in the Khibiny mountains was discovered by V.F. Perov in 1958. Since then and until the beginning of the 21st study of glaciers in this area has not been carried out. In general, warming is recorded on the Kola Peninsula. The average annual increase in temperature is 2.3°C ± 1°C during the last 50 years, which correlates with the data of other researchers. The glaciers in the Khibiny mountains should have significantly reduced their size in this connection. In other Arctic regions degradation of glaciation is noted. Some researchers predicted to disappear of Khibiny glaciation. In order to assess the change in glacier areas, we carried out a comprehensive study of small glaciers in the Khibiny mountains. We studied dynamics of glaciers over the past 15 years using field observations and the use of GIS and remote sensing methods. In our study, we used aerial photographs of 1958, digital models built on the basis of field measurements, and satellite images for years different in meteorological parameters. Our research shows, despite the slight degradation of glaciation, this tendency is modest and glaciers’ area remains relatively stable. Our research shows that glaciers shrank significantly in the early 2000s and showed a tendency towards complete disappearance. Their area has decreased by more than two times compared to the figures obtained in 1958. This fact may be caused by the increase in snow precipitation through in recent years. After 2007, there has been an increase in snow precipitation. In subsequent years, starting in 2008, the glaciers began to regain their size. Over the past 15 years, the average area of two glaciers (No. 3 and No. 4) exceeds the size of 1958. Glaciers No. 1 and No. 2 have shrinkage.
38
Steinke, Stephan, Markus Kienast, Uwe Pflaumann, Mara Weinelt e Karl Stattegger. "A High-Resolution Sea-Surface Temperature Record from the Tropical South China Sea (16,500–3000 yr B.P.)". Quaternary Research 55, n. 3 (maggio 2001): 352–62. http://dx.doi.org/10.1006/qres.2001.2235.
Abstract (sommario):
AbstractThe timing and magnitude of sea-surface temperature (SST) changes in the tropical southern South China Sea (SCS) during the last 16,500 years have been reconstructed on a high-resolution, 14C-dated sediment core using three different foraminiferal transfer functions (SIMMAX28, RAM, FP-12E) and geochemical (Uk′37) SST estimates. In agreement with CLIMAP reconstructions, both the FP-12E and the Uk′37 SST estimates show an average late glacial–interglacial SST difference of 2.0°C, whereas the RAM and SIMMAX28 foraminiferal transfer functions show only a minor (0.6°C) or no consistent late glacial–interglacial SST change, respectively. Both the Uk′37 and the FP-12E SST estimates, as well as the planktonic foraminiferal δ18O values, indicate an abrupt warming (ca. 1°C in <200 yr) at the end of the last glaciation, synchronous (within dating uncertainties) with the Bølling transition as recorded in the Greenland Ice Sheet Project 2 (GISP2) ice core, whereas the RAM-derived deglacial SST increase appears to lag during this event by ca. 500 yr. The similarity in abruptness and timing of the warming associated with the Bølling transition in Greenland and the southern SCS suggest a true synchrony of the Northern Hemisphere warming at the end of the last glaciation. In contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the Younger Dryas (YD) climate event in the tropical SCS, the Uk′37 SST estimates show a cooling of ca. 0.2–0.6°C compared to the Bølling–Allerød period. These Uk′37 SST estimates from the southern SCS argue in favor of a Northern Hemisphere-wide, synchronous cooling during the YD period.
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Mikhalenko, Vladimir N. "Changes in Eurasian glaciation during the past century: glacier mass balance and ice-core evidence". Annals of Glaciology 24 (1997): 283–87. http://dx.doi.org/10.3189/s0260305500012313.
Abstract (sommario):
Glaciers of both the Arctic and mid-latitude mountain systems within Eurasia have retreated intensively during the past century. Measured and reconstructed glacier mass balances show that glacier retreat began around the 1880s. The mean annual mass-balance value for 1880–1990 was −480 mm a−1 for glaciers with maritime climatic conditions, and −140 mm a−1 for continental glaciers. It can be concluded that warming in the Caucasus occurred during at least the last 60 years, according to the distribution of crystal sizes in an ice core from the Dzhantugan firn plateau. Temperatures measured in 1962 at 20 m on the Gregoriev ice cap, Tien Shan, were −4.2°C while in 1990 they were −2°C, a warming of 2.2°C over 28 years. Changes in the isotopic composition of glacier ice during the 20th century indicate recent and continuing warming in different regions of Eurasia. The δ18O records reveal an enrichment at the Gregoriev ice cap during the last 50 years, while surface temperatures at the Tien Shan meteorological station have increased 0.5°C since 1930.
40
Mikhalenko, Vladimir N. "Changes in Eurasian glaciation during the past century: glacier mass balance and ice-core evidence". Annals of Glaciology 24 (1997): 283–87. http://dx.doi.org/10.1017/s0260305500012313.
Abstract (sommario):
Glaciers of both the Arctic and mid-latitude mountain systems within Eurasia have retreated intensively during the past century. Measured and reconstructed glacier mass balances show that glacier retreat began around the 1880s. The mean annual mass-balance value for 1880–1990 was −480 mm a−1 for glaciers with maritime climatic conditions, and −140 mm a−1 for continental glaciers. It can be concluded that warming in the Caucasus occurred during at least the last 60 years, according to the distribution of crystal sizes in an ice core from the Dzhantugan firn plateau. Temperatures measured in 1962 at 20 m on the Gregoriev ice cap, Tien Shan, were −4.2°C while in 1990 they were −2°C, a warming of 2.2°C over 28 years. Changes in the isotopic composition of glacier ice during the 20th century indicate recent and continuing warming in different regions of Eurasia. The δ 18O records reveal an enrichment at the Gregoriev ice cap during the last 50 years, while surface temperatures at the Tien Shan meteorological station have increased 0.5°C since 1930.
41
Turon, Jean-Louis, Anne-Marie Lézine e Michelle Denèfle. "Land–sea correlations for the last glaciation inferred from a pollen and dinocyst record from the Portuguese margin". Quaternary Research 59, n. 1 (gennaio 2003): 88–96. http://dx.doi.org/10.1016/s0033-5894(02)00018-2.
Abstract (sommario):
AbstractPollen and dinoflagellate cyst assemblages from Core SU 81-18 recovered off Portugal (37°46′N, 10°11′W; 3135-m water depth) have been used to document the short-term environmental changes that occurred in southwest Europe since 25,000 yr B.P. The relationship between the oceanic and continental environments has been further examined by the use of other marine proxies (coarse sedimentary fraction, foraminifera) and by comparison with proximal land pollen records. Heinrich 2 (H2) and Heinrich 1 (H1) events were the most extreme parts of the highly variable last glacial period, with the maximum extension of dry steppe on land and the occurrence of cool and dilute waters at the core site. Our study shows that H1 and H2 are divided in two distinct phases: one with Neogloboquadrina pachyderma left coiling associated with the maximum input of ice rafted debris, reflecting the in situ release of icebergs and the occurrence of cool and dilute seawater at the core site; the other with dinoflagellate cysts of subpolar affinity, Bitectatodinium tepikiense, reflecting a seasonal control marked by warm summer SST and cold winter SST.
42
Stauch, Georg, e Frank Lehmkuhl. "Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia". Quaternary Research 74, n. 1 (luglio 2010): 145–55. http://dx.doi.org/10.1016/j.yqres.2010.04.003.
Abstract (sommario):
AbstractGeomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50 ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90 ka, moraine IV is 100 to 120 ka, and the outermost moraine V was deposited around 135 ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets.
43
Waythomas, Christopher F., Peter D. Lea e Robert C. Walter. "Stratigraphic Context of Old Crow Tephra, Holitna Lowland, Interior Southwest Alaska". Quaternary Research 40, n. 1 (luglio 1993): 20–29. http://dx.doi.org/10.1006/qres.1993.1052.
Abstract (sommario):
AbstractA thick deposit of Old Crow tephra was discovered in a bluff exposure along the middle Holitna River near the Kulukbuk Hills (61°20′N latitude, 157°10′W longitude) in interior southwest Alaska. This locality is the southwesternmost-known deposit of Old Crow tephra in Alaska. Thickness and grain-size data from this site support a source volcano in the eastern Aleutian arc. Pleistocene stratigraphic sequences in the lowland are dominated by upward-fining eolian sand-sheet deposits and loess separated by organic silt. These deposits record at least two episodes of regional glaciation and an intervening nonglacial period (marine oxygen isotope stage 3, stage 5, or both). Old Crow tephra crops out near the top of the lower upward-fining eolian unit, indicating that the ash erupted near the end of an interval of periglacial eolian sedimentation. The sequence of eolian deposits that contain Old Crow tephra probably accumulated during the latter part of marine oxygen isotope stage 6, whereas the overlying eolian sequence formed during the last glaciation (stage 2). This stratigraphic position is consistent with other stratigraphic contexts for the tephra and with fission-track and thermoluminescence ages of ca. 140,000 ± 10,000 yr B.P.
44
Atkinson, Nigel, Daniel J. Utting e Steven M. Pawley. "Landform signature of the Laurentide and Cordilleran ice sheets across Alberta during the last glaciation". Canadian Journal of Earth Sciences 51, n. 12 (dicembre 2014): 1067–83. http://dx.doi.org/10.1139/cjes-2014-0112.
Abstract (sommario):
Government geological survey maps and research publications have portrayed the distribution of glacial landforms associated with the advance and retreat of the Laurentide and Cordilleran ice sheets across Alberta at a local, regional, and continental scale. To date, this information has not been systematically synthesized into a single compilation at a consistent scale. Although this original work provided valuable information to constrain reconstructions of former ice sheet extent, configuration, and flow geometry, its derivation primarily from the interpretation of aerial photographs and the Shuttle Radar Topography Mission 90 m digital elevation model (DEM) may result in methodological inconsistencies and spatial biases. These biases, together with challenges associated with geomorphic mapping in densely forested areas of western and northern Alberta limit the usefulness of previous mapping when applied to inversion-based ice sheet reconstructions, which have specific input data demands. Recently, light detection and ranging (LiDAR) DEMs have become increasingly available throughout Alberta. Hill-shaded imagery of these data provides unprecedented geomorphic detail beneath the forest cover and reveals that that the glacial geomorphology of northern and western Alberta is more complex than previously recognized. In this paper, we describe the methodology and geomorphic criteria used to produce a glacial landform map of Alberta using previously published data, supplemented by comprehensive new analysis of high-resolution (2–25 m) DEMs. These include 306 624 km2 of LiDAR imagery, with which it is now possible to verify and where necessary augment previous mapping, particularly across areas with a dense forest cover.
45
Wang, Jie, Christine Kassab, Jonathan M. Harbor, Marc W. Caffee, Hang Cui e Guoliang Zhang. "Cosmogenic nuclide constraints on late Quaternary glacial chronology on the Dalijia Shan, northeastern Tibetan Plateau". Quaternary Research 79, n. 3 (maggio 2013): 439–51. http://dx.doi.org/10.1016/j.yqres.2013.01.004.
Abstract (sommario):
AbstractCosmogenic nuclide (CN) apparent exposure dating has become a widely used method for determining the age of glacial landforms on the Tibetan Plateau with > 1200 published ages. We present the first 10Be exposure ages from the Dalijia Shan, the most northeastern formerly glaciated mountain range on the Tibetan Plateau. The moraine groups identified from field and remote sensing imagery mapping record four glacial events at 37.07 ± 3.70 to 52.96 ± 4.70 ka (MIS 3), 20.17 ± 1.79 to 26.99 ± 2.47 ka (MIS 2), 16.92 ± 1.49 to 18.76 ± 1.88 ka (MIS 2), and 11.56 ± 1.03 to 11.89 ± 1.06 ka (Younger Dryas). These ages indicate that glaciation in the northeastern Tibetan Plateau is much younger than previously thought. In addition, this record is consistent with many other regions on the Tibetan Plateau, with a local last glacial maximum during MIS 3 asynchronous with Northern Hemisphere last glacial maximum during MIS 2. The Dalijia Shan might also include an event of Younger Dryas age, but this needs to be tested in future studies.
46
England, John, I. Rod Smith e David JA Evans. "The last glaciation of east-central Ellesmere Island, Nunavut: ice dynamics, deglacial chronology, and sea level change". Canadian Journal of Earth Sciences 37, n. 10 (1 ottobre 2000): 1355–71. http://dx.doi.org/10.1139/e00-060.
Abstract (sommario):
During the last glacial maximum of east-central Ellesmere Island, trunk glaciers inundated the landscape, entering the Smith Sound Ice Stream. Accelerator mass spectrometry (AMS) dates on individual shell fragments in till indicate that the ice advanced after 19 ka BP. The geomorphic and sedimentary signatures left by the trunk glaciers indicate that the glaciers were polythermal. The configuration and chronology of this ice is relevant to the reconstruction of ice core records from northwestern Greenland, the history of iceberg rafting of clastic sediments to northern Baffin Bay, the reopening of the seaway between the Arctic Ocean and Baffin Bay, and the regional variability of arctic paleoenvironments. Deglaciation began with the separation of Ellesmere Island and Greenland ice at fiord mouths ~8-8.5 ka BP. Ice reached fiord heads between 6.5 and 4.4 ka BP. Trunk glacier retreat from the fiords of east-central Ellesmere Island occurred up to 3000 years later than in west coast fiords. This later retreat was favoured by (1) impoundment by the Smith Sound Ice Stream in Kane Basin until ~8.5 ka BP, which moderated the impact of high summer melt recorded in nearby ice cores between ~11.5 and 8.5 ka BP; (2) the shallow bathymetry and narrowness (<2 km) of the east coast fiords, which lowered calving rates following separation of Innuitian and Greenland ice; and (3) the likelihood of higher precipitation along east Ellesmere Island. Glaciers throughout the field area readvanced during the late Holocene. The greater advance of coastal glaciers is attributed to their proximity to the North Water polynya in Baffin Bay.
47
Liu, Yuming, Xingxing Liu, Long Ma, Shugang Kang, Xiaoke Qiang, Fei Guo e Youbin Sun. "Temporal–spatial variations in aeolian flux on the Chinese Loess Plateau during the last 150 ka". Geological Magazine 157, n. 5 (14 novembre 2019): 757–67. http://dx.doi.org/10.1017/s0016756819001067.
Abstract (sommario):
AbstractAeolian dust deposits from continent and ocean have been extensively investigated to reflect past changes in source aridity and atmospheric circulations. Aeolian flux (AF) as a quantitative dust proxy has been widely used in both palaeoenvironmental reconstruction and numerical simulation. However, available AF data on the Chinese Loess Plateau (CLP) is too limited to assess the temporal–spatial variations at glacial–interglacial timescales, and therefore cannot be used as robust input parameters in palaeoclimate models. Here we investigate eight loess profiles along two N–S-aligned transects on the CLP to quantitatively estimate the AF variations over the last glacial–interglacial cycle. We first establish a refined chronological framework based on optically stimulated luminescence chronology and pedostratigraphic correlation. AF was then estimated by multiplying the sedimentation rate and bulk density. The results show that the AF increases from 2–18 g cm−2 ka−1 in the southeastern CLP to 14–105 g cm−2 ka−1 in the northwestern CLP. At glacial–interglacial scales, the AF varies from 2–20 g cm−2 ka−1 during the last interglacial to 8–105 g cm−2 ka−1 in the last glaciation. Due to more spatial coverage and better age constraints, our AF data can be used to refine other AF datasets and to improve the proxy–model comparison.
48
Donat, M., e F. Kaspar. "Simulations of the last interglacial and the subsequent glacial inception with the Planet Simulator". Climate of the Past Discussions 2, n. 6 (13 dicembre 2006): 1347–69. http://dx.doi.org/10.5194/cpd-2-1347-2006.
Abstract (sommario):
Abstract. The Planet Simulator was used to perform equilibrium simulations of the Eemian interglacial at 125 kyBP and the glacial inception at 115 kyBP. Additionally, an accelerated transient simulation of that interval was performed. During this period the changes of Earth's orbital parameters led to a reduction of summer insolation in the northern latitudes. The model has been run in different configurations in order to evaluate the influence of the individual sub-models. The strongest reaction on the insolation change was observed when the atmosphere was coupled with all available sub-systems: a mixed-layer ocean and a sea-ice model as well as a vegetation model. In the simulations representing the interglacial, the near-surface temperature in northern latitudes is higher compared to the preindustrial reference run and almost no perennial snow cover occurs. In the run for the glacial inception, wide areas in mid and high northern latitudes show negative temperature anomalies and wide areas are covered by snow or ice. The transient simulation shows that snow volume starts to increase after summer insolation has fallen below a critical value. The main reason for the beginning glaciation is the locally reduced (summer) temperature as a consequence of reduced summer insolation. Therefore, a larger fraction of precipitation falls as snow and less snow can melt. That mechanism is amplified by the snow-albedo-feedback.
49
Starovoytov, A. V., M. Yu Tokarev, Ya E. Terehina e N. A. Kozupitsa. "THE SEDIMENTARY COVER STRUCTURE OF THE KANDALAKSHA GULF OF THE WHITE SEA) ACCORDING TO CONTINUOUS SEISMIC PROFILING DATA". Moscow University Bulletin. Series 4. Geology, n. 2 (28 aprile 2018): 81–92. http://dx.doi.org/10.33623/0579-9406-2018-2-81-92.
Abstract (sommario):
The geological structure of the water area adjacent to the White Sea biological research station of the Moscow State University (the Rugoserskaya bay and the Great Salma strait, the Kandalaksha gulf of the White Sea) was examined for the first time basing on seismoacoustic data. The morphology of top of the Archaean basement, the structure of the Quaternary sedimentary cover and the bottom topography were studied. A sequence of glacial deposits dating back to the last glaciation and a compound sequence of glaciolacustrine, glacial-marine and marine sediments were delineated. Spatial configuration and thickness behavior were examined. It was demonstrated that the recent bottom topography is controlled by the faults, characterized predominantly by north-western and the north-eastern strike, and affecting the entire sedimentary cover including the Holocene sediments.
50
Beghin, P., S. Charbit, C. Dumas, M. Kageyama, D. M. Roche e C. Ritz. "Interdependence of the Northern Hemisphere ice-sheets build-up during the last glaciation: the role of atmospheric circulation". Climate of the Past Discussions 9, n. 2 (18 aprile 2013): 2183–216. http://dx.doi.org/10.5194/cpd-9-2183-2013.
Abstract (sommario):
Abstract. The development of large continental-scale ice sheets over Canada and Northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial-interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI, we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. Several parameterizations have been tested allowing to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. We show that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly be explained by the feedbacks mechanisms occurring between ice sheets and atmospheric circulation.