scholarly journals Human Settlements and the Last Deglaciation in the French Alps

Radiocarbon ◽  
1994 ◽  
Vol 36 (3) ◽  
pp. 345-357 ◽  
Author(s):  
Jacques Evin ◽  
Pierre Bintz ◽  
Guy Monjuvent
Keyword(s):  
Eastern Alps ◽  
Simultaneous Occurrence ◽  
Last Deglaciation ◽  
Glacial Retreat ◽  
French Alps ◽  
Dating Method ◽  
The Last Deglaciation ◽  
Rhone Valley ◽  
Glacial Advance ◽  
The Last Glacial

According to most geological and geomorphological studies, the maximal advance of the Würmian glaciers in the French Alps occurred at least before 40 ka bp and cannot be dated by 14C. Scientists believed that this dating method could be used for dating the last glacial advance and late deglaciation in the region. The scarce and scattered 14C dating results available from geological samples do not confirm an early (ca. 18 or 20 ka bp) age for the total cooling of the ice nor do they prove that residual ice sheets remained at low elevations. Attempting to solve this chronological problem, we compiled current archaeological knowledge of the oldest Late Paleolithic sites. A review of their 14C results shows that no site older than 15 ka bp (with Gravettian, Solutrean or early Magdalenian industries) can be found east of the Saône-Rhône Valley, even at low elevations. Only rare sites, dated to ca. 14.5 ka bp, may be found close to the mountain regions that were suddenly occupied around the beginning of the Bølling period (ca. 13.5 ka bp). Thus, it seems that the eastern Alps offer no evidence for direct association between glacial retreat and human settlement or simultaneous occurrence in early or late deglaciated areas.

scholarly journals Eemian estuarine record forced by glacio-isostasy (southern Iceland)—link with Greenland and deep sea records

2018 ◽  
Vol 55 (2) ◽  
pp. 154-171 ◽  
Author(s):  
Brigitte Van Vliet-Lanoë ◽  
Jean-Luc Schneider ◽  
Águst Guðmundsson ◽  
Hervé Guillou ◽  
Sébastien Nomade ◽  
...  
Keyword(s):  
Ice Core ◽  
Sedimentary Facies ◽  
Last Deglaciation ◽  
Last Interglacial ◽  
Glacial Retreat ◽  
Cold Events ◽  
Loess Deposition ◽  
The Last Deglaciation ◽  
Mis 5E ◽  
Glacial Advance

Central southern Iceland is one of the main outlets of the Icelandic Ice Sheet where a MIS 5e sedimentary complex, the Rangá Formation, is extensively observed below the last deglaciation terminal moraines. Sedimentary facies demonstrate that the Rangá Formation is mostly tidal, up to 215 m (transgression I) and 168 m (transgression II) in altitude. The first highstand reworks a thick tephra from the Grimsvötn volcano, known in marine cores as 5e low/Bas-IV and positioned at ca. 127 Ka BP, the Eemian thermal optimum. This formation is related to a rapid deglaciation followed by two marine transgressions marked by the development of extended mud flats, which were separated by a complex regression phase, associated with loess deposition, ca. 9 Ka in duration. Palaeo jökulhlaups, basaltic flows, and tephra fallouts from the Hekla and Grimsvötn volcanoes affected the sedimentation. The Rangá Formation yields one of the first continuous and complete estuarine records of the Eemian interglacial in Iceland and probably for most of the northern terrestrial Atlantic. This estuarine infill records the distal signature of a complex glacial advance within the last interglacial, already well identified in northern and central Iceland. The glacial advance is attributed to the intra-Eemian cooling events (Greenland GS 26 or marine cold events M-C25-C26). It is followed by a warming and a glacial retreat corresponding to the Greenland GI 25 event. This formation allows, in connection with the timing of recognized volcanic periods, a better insight of the interconnections between sea-level, regional glacial extent, and Northern Hemisphere marine and ice core climatic records.

A 45 kyr laminae record from the Dead Sea: Implications for basin erosion and floods recurrence

2020 ◽  
Author(s):  
Nicolas Waldmann ◽  
Yin Lu ◽  
Revital Bookman ◽  
Shmulik Marco
Keyword(s):  
High Frequency ◽  
Lake Level ◽  
Dead Sea ◽  
Last Deglaciation ◽  
The Holocene ◽  
Lamina Thickness ◽  
The Last Deglaciation ◽  
The Dead ◽  
Basin Erosion ◽  
The Last Glacial

<p>Recording and analyzing how climate change impacts flood recurrence, basin erosion, and sedimentation can improve our understanding of these systems. The aragonite-detritus laminae couplets comprising the lacustrine formations that were deposited in the Dead Sea Basin are considered as faithful monitors of the freshwater supply to the lakes. We count a total of ~5600 laminae couplets deposited in the last 45 kyr (MIS3-MIS1) at the Dead Sea depocenter, which encompass the upper 141.6 m of the ICDP Core 5017-1. The present study shows that aragonite and detritus laminae are thinner and occur at high frequency during MIS 3-2, while they are much thicker and less frequent during MIS 1. By analyzing multiple climate-connected factors, we propose that significant lake-level drops, enhanced dust input, and low vegetative cover in the drainage basin during the last deglaciation (22-11.6 ka) have considerably increased erodible materials in the Dead Sea watershed. We find a decoupling existed between the significant lake-level drop/lake size reduction and lamina thickness change during the last deglaciation. We argue that during the last glacial and the Holocene, the variation of lamina thickness at the multiple-millennium scale was not controlled directly by the lake-level/size change. We interpret this decoupling implying the transport capacity of flash-floods is low and might be saturated by the oversupply of erodible materials, and indicating a transport-limited regime during the time period. We suggest that the observed thickness and frequency distribution of aragonite-detritus laminae points to the high frequency of small-magnitude floods during the last glacial period, in contrast to low frequency, but large-magnitude floods during the Holocene.</p>

scholarly journals Cancelation of Deglacial Thermosteric Sea Level Rise by a Barosteric Effect

2020 ◽  
Vol 50 (12) ◽  
pp. 3623-3639
Author(s):  
Geoffrey Gebbie
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Steric Effect ◽  
Three Dimensional ◽  
Steric Effects ◽  
Last Deglaciation ◽  
Effect Analysis ◽  
Height Change ◽  
The Last Deglaciation ◽  
The Last Glacial

AbstractSea level rise over the last deglaciation is dominated by the mass of freshwater added to the oceans by the melting of the great ice sheets. While the steric effect of changing seawater density is secondary over the last 20 000 years, processes connected to deglacial warming, the redistribution of salt, and the pressure load of meltwater all influence sea level rise by more than a meter. Here we develop a diagnostic for steric effects that is valid when oceanic mass is changing. This diagnostic accounts for seawater compression due to the added overlying pressure of glacial meltwater, which is here defined to be a barosteric effect. Analysis of three-dimensional global seawater reconstructions of the last deglaciation indicates that thermosteric height change (1.0–1.5 m) is counteracted by barosteric (−1.9 m) and halosteric (from −0.4 to 0.0 m) effects. The total deglacial steric effect from −0.7 to −1.1 m has the opposite sign of analyses that assume that thermosteric expansion is dominant. Despite the vertical oceanic structure not being well constrained during the Last Glacial Maximum, net seawater contraction appears robust as it occurs in four reconstructions that were produced using different paleoceanographic datasets. Calculations that do not account for changes in ocean pressure give the misleading impression that steric effects enhanced deglacial sea level rise.

scholarly journals Origin of the Phoksundo Tal (lake), Dolpa district, western Nepal

1997 ◽  
Vol 15 ◽  
Author(s):  
H. Yagi
Keyword(s):  
Glacial Retreat ◽  
Last Glacial ◽  
Geomorphic Features ◽  
Glacial Advance ◽  
The Last Glacial

The typical geomorphic features of a landslide such as horseshoe shaped steep scarp and debris mounds are observed adjacent to the southeastern end of the Phoksundo Lake. The mounds consist of rock detritus ranging from cobble size to boulders of several tens of meters in diameter. The total volume of the debris deposited on the left side of the Bauli Gad is estimated to be about l.5 billion m3. The Phoksundo Lake is originated due to landslide damming resulting from a mountain collapse. The detritus is overlying the glacial drift. It implies that one of the glacial valley walls became unstable after the glacial retreat and collapsed over its own glacial drift, probably triggered by an earthquake. The mountain collapse may have occurred around 30 to 40 ka, just after the early substage of the glacial advance in the Last Glacial age.

scholarly journals CH<sub>4</sub> and N<sub>2</sub>O fluctuations during the penultimate deglaciation

2021 ◽  
Vol 17 (4) ◽  
pp. 1627-1643
Author(s):  
Loïc Schmidely ◽  
Christoph Nehrbass-Ahles ◽  
Jochen Schmitt ◽  
Juhyeong Han ◽  
Lucas Silva ◽  
...  
Keyword(s):  
Ice Core ◽  
Last Deglaciation ◽  
Glacial Cycle ◽  
Last Glacial Period ◽  
Modes Of Variability ◽  
The Past ◽  
Present Composite ◽  
The Last Deglaciation ◽  
Ch4 And N2o ◽  
The Last Glacial

Abstract. Deglaciations are characterized by the largest natural changes in methane (CH4) and nitrous oxide (N2O) concentrations of the past 800 000 years. Reconstructions of millennial- to centennial-scale variability within these periods are mostly restricted to the last deglaciation. In this study, we present composite records of CH4 and N2O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of ∼100 years. Our data permit the identification of centennial-scale fluctuations during the transition from glacial to interglacial levels. At ∼134 000 and ∼129 000 years before present (hereafter ka), both CH4 and N2O increased on centennial timescales. These abrupt rises are similar to the fluctuations associated with the Dansgaard–Oeschger events identified in the last glacial period. In addition, gradually rising N2O levels at ∼130 ka resemble a pattern of increasing N2O concentrations on millennial timescales characterizing the later part of Heinrich stadials. Overall, the events in CH4 and N2O during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation and glacial cycle, suggesting that the processes leading to changes in emission during the transitions were similar but their timing differed.

Characterising Dansgaard-Oeschger cycles: from MIS3 to today

2021 ◽  
Author(s):  
Heather Andres ◽  
Lev Tarasov
Keyword(s):  
Climate Changes ◽  
Ice Cores ◽  
Ocean Dynamics ◽  
System Model ◽  
Last Deglaciation ◽  
Large Magnitude ◽  
Atmospheric Physics ◽  
The Last Deglaciation ◽  
The Last Glacial Maximum ◽  
The Last Glacial

&lt;p&gt;One of the main contributors to palaeoclimate variability on millennial timescales is understood to be Dansgaard-Oeschger (D-O) cycles. Our awareness of these phenomena arises primarily from quasi-periodic, abrupt transitions of large magnitude detected in &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O records from Greenland ice cores (e.g. Dansgaard et al, 1982; Johnsen et al, 1992), although there is evidence of similar variability in other archives and regions. D-O cycles have plenty to capture the imagination:&lt;/p&gt;&lt;ul&gt;&lt;li&gt; &lt;p&gt;the strength and rapidity of climate changes over Greenland,&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;their regularity throughout MIS3 (~60 to 30 thousand years before present) and occurrence during the last deglaciation contrasting with their relative absence during the Last Glacial Maximum and Holocene,&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;their opposed characteristics in Greenland and Antarctica,&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;and that different models require different boundary conditions to reproduce this phenomena, if they can reproduce it at all.&lt;/p&gt; &lt;/li&gt; &lt;/ul&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;This talk characterises D-Olike cycles in two different models: Planet Simulator (PlaSim, an Earth System Model with simplified atmospheric physics, thermodynamic sea ice, and simplified ocean dynamics), and COSMOS (a CMIP3-era ESM). We identify four phases to D-O cycles and commonalities and differences in their representations in these models. Finally, we examine which phases of this type of variability continue to contribute to climate variability today and what that looks like.&lt;/p&gt;

scholarly journals Antarctic ice dynamics amplified by Northern Hemisphere sea level forcing

2021 ◽  
Author(s):  
Natalya Gomez ◽  
Michael Weber ◽  
Peter Clark ◽  
Jerry Mitrovica ◽  
Holly Han
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Grounding Line ◽  
The Last Deglaciation ◽  
Global Sea Level ◽  
The Last Glacial Maximum ◽  
The Last Glacial

&lt;p&gt;A longstanding hypothesis for near-synchronous evolution of global ice sheets over ice-age cycles invokes an interhemispheric sea-level forcing whereby sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing causes grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS). Recent studies have shown that the AIS experienced substantial millennial-scale variability during and after the last deglaciation, with several times of recorded increased iceberg flux and grounding line retreat coinciding, within uncertainty, with well documented global sea-level rise events, providing further evidence of this sea-level forcing. However, the sea level changes associated with ice sheet mass loss are strongly nonuniform due to gravitational, deformational and Earth rotational effects, suggesting that the response of the AIS to Northern Hemisphere sea-level forcing is more complicated than previously modelled.&lt;/p&gt;&lt;p&gt;We adopt an ice-sheet model coupled to a global sea-level model to show that a large or rapid Northern Hemisphere sea-level forcing enhances grounding-line advance and associated mass gain of the AIS during glaciation, and grounding-line retreat and AIS mass loss during deglaciation. Relative to models without these interactions, including the Northern Hemisphere sea-level forcing leads to a larger AIS volume during the Last Glacial Maximum (about 26,000 to 20,000 years ago), subsequent earlier grounding-line retreat and millennial-scale AIS variability throughout the last deglaciation. These findings are consistent with geologic reconstructions of the extent of the AIS during the Last Glacial Maximum and subsequent ice-sheet retreat, and with relative sea-level change in Antarctica.&amp;#160;&lt;/p&gt;

Cirque glacier activity in arctic Norway during the last deglaciation

2007 ◽  
Vol 68 (3) ◽  
pp. 387-399 ◽  
Author(s):  
Øyvind Paasche ◽  
Svein Olaf Dahl ◽  
Jostein Bakke ◽  
Reidar Løvlie ◽  
Atle Nesje
Keyword(s):  
Regional Distribution ◽  
Lacustrine Sediments ◽  
Younger Dryas ◽  
Last Deglaciation ◽  
Visual Interpretation ◽  
Dry Period ◽  
Equilibrium Line Altitude ◽  
Glacial Retreat ◽  
Magnetic Parameters ◽  
The Last Deglaciation

AbstractNumerous cirques of the Lofoten–Vesterålen archipelago in northern Norway have distinct moraine sequences that previously have been assigned to the Allerød-Younger Dryas (∼ 13,400 to 11,700 yr BP) interval, constraining the regional distribution of the equilibrium-line altitude (ELA) of cirque and valley glaciers. Here we present evidence from a once glacier-fed lake on southern Andøya that contests this view. Analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters, grain size, organic matter, dry bulk density and visual interpretation suggest that no glacier was present in the low-lying cirque during the Younger Dryas-Allerød. The initiation of the glacial retreat commenced with the onset of the Bølling warming (∼ 14,700 yr BP) and was completed by the onset of Allerød Interstade (∼ 13,400 yr BP). The reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from ∼ 17,500 to 14,700 yr BP and a somewhat larger Last Glacial Maximum (LGM) advance possibly occurring between ∼ 21,050 and 19,100 yr BP.

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