scholarly journals An international palaeo-environmental project at Paakitsoq, West Greenland

1995 ◽  
Vol 165 ◽  
pp. 88-92
Author(s):  
H.H Thomsen ◽  
P.E Biscaye ◽  
J.C Bourgeois ◽  
C.E Bøggild ◽  
H Oerter ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Environmental Parameters ◽  
Glacial Cycle ◽  
Joint Project ◽  
Large Samples ◽  
Ice Velocity ◽  
Age Range ◽  
Made In ◽  
The Last Glacial

The easily accessible ice at Paakitsoq offers a favourable opportunity to study the major climatic events that occurred during the last glacial cycle, since large samples of ice with a limited age-range can be obtained. In this sense the ice margin record is an alternative to the deep ice-core records where the number of environmental parameters that can be studied is limited by the amount of ice available, each parameter requiring a certain amount of ice for its analysis (Reeh et al., 1993). This possibility has attracted the attention of scientists working with environmental parameters requiring large ice samples. A Danish, American, Canadian and German joint project was therefore initiated, and in April 1994 a programme of retrieving ice samples for studies of pollen, dust, chemistry, textures, fabric and visual stratigraphy was carried out. Furthermore, measurements of mass balance, ice velocity and deformation were made. In addition to the possibility of studying the variation of environmental parameters over a full glacial cycle, the project will also support the establishment of a better chronology along the Paakitsoq profile.

scholarly journals Measured Velocities of Interior East Antarctica and the State of Mass Balance Within the I.A.G.P. Area

1979 ◽  
Vol 24 (90) ◽  
pp. 77-87 ◽  
Author(s):  
N. W. Young
Keyword(s):  
Mass Balance ◽  
Total Mass ◽  
East Antarctica ◽  
Velocity Measurements ◽  
Drainage Basins ◽  
Mass Budget ◽  
Large Sector ◽  
Ice Velocity ◽  
True Mass ◽  
Made In

AbstractRecent measurements of accumulation and ice velocity made in the interior of East Antarctica indicate that a large sector between longitudes 80° E. and 135° E. and north of latitude 80° S. has close to a zero net mass budget. This sector is within the study area for the International Antarctic Glaciological Project (I.A.G.P.) and covers a major portion of the area indicated for projects of special emphasis. Velocity measurements were made at a number of points on a traverse route from Mirny (lat. 66° 33′ S., long. 93°00′ E.) on the coast Dome “C” (lat. 74° 40′ S., long. 124° 00′ E.), in the interior. Accumulation measurements were made along this and other traverse routes, extending as far as Vostok (lat. 78° 28′ S., long. 106° 50′ E.), by a number of methods. These included stake, stratigraphic, isotopic, and totalβ-decay observations. The better accumulation data have allowed a review of the total mass input to be made. The true mass budget has been estimated by comparing velocities, calculated assuming a zero net mass budget with measured velocities along the traverse routes and on a number of the outlet glaciers. For this purpose the area was divided into a number of drainage basins according to outlet at the coast. The area of about 106km2and 150 Gt a−1flux input is drained primarily by three glacier systems of which the Totten accounts for 40% of the flux from 55% of the area; the Vanderford 20% from 15%; and the Scott/Denman 20% from 20%.

scholarly journals Simulation of the last glacial cycle with a coupled climate ice-sheet model of intermediate complexity

2010 ◽  
Vol 6 (2) ◽  
pp. 229-244 ◽  
Author(s):  
A. Ganopolski ◽  
R. Calov ◽  
M. Claussen
Keyword(s):  
Surface Energy ◽  
Mass Balance ◽  
Spatial Dynamics ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Atmospheric Concentration ◽  
Last Glacial ◽  
Intermediate Complexity ◽  
The Last Glacial

Abstract. A new version of the Earth system model of intermediate complexity, CLIMBER-2, which includes the three-dimensional polythermal ice-sheet model SICOPOLIS, is used to simulate the last glacial cycle forced by variations of the Earth's orbital parameters and atmospheric concentration of major greenhouse gases. The climate and ice-sheet components of the model are coupled bi-directionally through a physically-based surface energy and mass balance interface. The model accounts for the time-dependent effect of aeolian dust on planetary and snow albedo. The model successfully simulates the temporal and spatial dynamics of the major Northern Hemisphere (NH) ice sheets, including rapid glacial inception and strong asymmetry between the ice-sheet growth phase and glacial termination. Spatial extent and elevation of the ice sheets during the last glacial maximum agree reasonably well with palaeoclimate reconstructions. A suite of sensitivity experiments demonstrates that simulated ice-sheet evolution during the last glacial cycle is very sensitive to some parameters of the surface energy and mass-balance interface and dust module. The possibility of a considerable acceleration of the climate ice-sheet model is discussed.

scholarly journals Simulation of the last glacial cycle with a coupled climate ice-sheet model of intermediate complexity

2009 ◽  
Vol 5 (5) ◽  
pp. 2269-2309 ◽  
Author(s):  
A. Ganopolski ◽  
R. Calov ◽  
M. Claussen
Keyword(s):  
Surface Energy ◽  
Mass Balance ◽  
Spatial Dynamics ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Atmospheric Concentration ◽  
Last Glacial ◽  
Intermediate Complexity ◽  
The Last Glacial

Abstract. A new version of the Earth system model of intermediate complexity, CLIMBER-2, which includes the three-dimensional polythermal ice-sheet model SICOPOLIS, is used to simulate the last glacial cycle forced by variations of the Earth's orbital parameters and atmospheric concentration of major greenhouse gases. The climate and ice-sheet components of the model are coupled bi-directionally through a physically based surface energy and mass-balance interface. The model accounts for the time-dependent effect of aeolian dust on planetary and snow albedo. The model successfully simulates the temporal and spatial dynamics of the major Northern Hemisphere (NH) ice sheets, including rapid glacial inception, strong asymmetry between the ice-sheet growth phase and glacial termination. Spatial extent and elevation of the ice sheets during the last glacial maximum agree reasonably well with palaeoclimate reconstructions. A suite of sensitivity experiments demonstrates that simulated ice-sheet evolution during the last glacial cycle is very sensitive to some parameters of the surface energy and mass-balance interface and dust module. The possibility of a considerable acceleration of the climate ice-sheet model is discussed.

scholarly journals Dansgaard–Oeschger events: bifurcation points in the climate system

2013 ◽  
Vol 9 (1) ◽  
pp. 323-333 ◽  
Author(s):  
A. A. Cimatoribus ◽  
S. S. Drijfhout ◽  
V. Livina ◽  
G. van der Schrier
Keyword(s):  
High Resolution ◽  
Abrupt Change ◽  
Ice Core ◽  
Ice Sheets ◽  
Climate System ◽  
External Forcing ◽  
Glacial Cycle ◽  
Warning Signals ◽  
Climate Fluctuations ◽  
The Last Glacial

Abstract. Dansgaard–Oeschger events are a prominent mode of variability in the records of the last glacial cycle. Various prototype models have been proposed to explain these rapid climate fluctuations, and no agreement has emerged on which may be the more correct for describing the palaeoclimatic signal. In this work, we assess the bimodality of the system, reconstructing the topology of the multi-dimensional attractor over which the climate system evolves. We use high-resolution ice core isotope data to investigate the statistical properties of the climate fluctuations in the period before the onset of the abrupt change. We show that Dansgaard–Oeschger events have weak early warning signals if the ensemble of events is considered. We find that the statistics are consistent with the switches between two different climate equilibrium states in response to a changing external forcing (e.g. solar, ice sheets), either forcing directly the transition or pacing it through stochastic resonance. These findings are most consistent with a model that associates Dansgaard–Oeschger with changing boundary conditions, and with the presence of a bifurcation point.

scholarly journals Radar stratigraphy connecting Lake Vostok and Dome C, East Antarctica, constrains the EPICA/DMC ice core time scale

2013 ◽  
Vol 7 (1) ◽  
pp. 321-342 ◽  
Author(s):  
M. G. P. Cavitte ◽  
D. D. Blankenship ◽  
D. A. Young ◽  
M. J. Siegert ◽  
E. Le Meur
Keyword(s):  
Ice Core ◽  
Airborne Radar ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Last Glacial ◽  
Lake Vostok ◽  
The Last Glacial Maximum ◽  
Radar Technique ◽  
Ice Core Dating ◽  
The Last Glacial

Abstract. New airborne radar sounding surveys at 60 MHz are used to trace internal layering between the Vostok and EPICA Dome C ice core sites. Eleven layers, spanning two glacial cycles from the last glacial maximum back to the MIS 7c interglacial, are used to correlate the two ice core chronologies. Independent of palaeoclimate signals, radar sounding enables correlation of the timescales, with a radar depth uncertainty equivalent to hundreds of years, which is small relative to the ice core dating uncertainties of thousands of years. Along the radar transects, horizons belonging to the last glacial cycle are impacted by aeolian stratigraphic reworking that increases radar technique uncertainty for this interval. However, older layers are used to propagate the higher resolution Vostok ages to the lower resolution Dome C ice core using the Suwa and Bender (2008) Vostok O2 / N2 chronology to give a recalibration of the Parrenin et al. (2007) EPICA EDC3 timescale between 1597 m and 2216 m depth (126 ka to 247 ka age interval).

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.

scholarly journals Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

2017 ◽  
Vol 13 (7) ◽  
pp. 943-958 ◽  
Author(s):  
Daniel Baggenstos ◽  
Thomas K. Bauska ◽  
Jeffrey P. Severinghaus ◽  
James E. Lee ◽  
Hinrich Schaefer ◽  
...  
Keyword(s):  
Large Scale ◽  
Ice Core ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Climate Reconstructions ◽  
Age Model ◽  
Taylor Glacier ◽  
The Last Glacial

Abstract. Old ice for paleo-environmental studies, traditionally accessed through deep core drilling on domes and ridges on the large ice sheets, can also be retrieved at the surface from ice sheet margins and blue ice areas. The practically unlimited amount of ice available at these sites satisfies a need in the community for studies of trace components requiring large sample volumes. For margin sites to be useful as ancient ice archives, the ice stratigraphy needs to be understood and age models need to be established. We present measurements of trapped gases in ice from Taylor Glacier, Antarctica, to date the ice and assess the completeness of the stratigraphic section. Using δ18O of O2 and methane concentrations, we unambiguously identify ice from the last glacial cycle, covering every climate interval from the early Holocene to the penultimate interglacial. A high-resolution transect reveals the last deglaciation and the Last Glacial Maximum (LGM) in detail. We observe large-scale deformation in the form of folding, but individual stratigraphic layers do not appear to have undergone irregular thinning. Rather, it appears that the entire LGM–deglaciation sequence has been transported from the interior of the ice sheet to the surface of Taylor Glacier relatively undisturbed. We present an age model that builds the foundation for gas studies on Taylor Glacier. A comparison with the Taylor Dome ice core confirms that the section we studied on Taylor Glacier is better suited for paleo-climate reconstructions of the LGM due to higher accumulation rates.

scholarly journals NGRIP CH<sub>4</sub> concentration from 120 to 10 kyr before present and its relation to a δ<sup>15</sup>N temperature reconstruction from the same ice core

2014 ◽  
Vol 10 (2) ◽  
pp. 903-920 ◽  
Author(s):  
M. Baumgartner ◽  
P. Kindler ◽  
O. Eicher ◽  
G. Floch ◽  
A. Schilt ◽  
...  
Keyword(s):  
Ice Core ◽  
High Ratio ◽  
Interglacial Period ◽  
Atmospheric Methane ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
Concentration Difference ◽  
Temperature Variations ◽  
Last Glacial ◽  
The Last Glacial

Abstract. During the last glacial cycle, Greenland temperature showed many rapid temperature variations, the so-called Dansgaard–Oeschger (DO) events. The past atmospheric methane concentration closely followed these temperature variations, which implies that the warmings recorded in Greenland were probably hemispheric in extent. Here we substantially extend and complete the North Greenland Ice Core Project (NGRIP) methane record from the Preboreal Holocene (PB) back to the end of the last interglacial period with a mean time resolution of 54 yr. We relate the amplitudes of the methane increases associated with DO events to the amplitudes of the local Greenland NGRIP temperature increases derived from stable nitrogen isotope (δ15N) measurements, which have been performed along the same ice core (Kindler et al., 2014). We find the ratio to oscillate between 5 parts per billion (ppb) per °C and 18 ppb °C−1 with the approximate frequency of the precessional cycle. A remarkably high ratio of 25.5 ppb °C−1 is reached during the transition from the Younger Dryas (YD) to the PB. Analysis of the timing of the fast methane and temperature increases reveals significant lags of the methane increases relative to NGRIP temperature for DO events 5, 9, 10, 11, 13, 15, 19, and 20. These events generally have small methane increase rates and we hypothesize that the lag is caused by pronounced northward displacement of the source regions from stadial to interstadial. We further show that the relative interpolar concentration difference (rIPD) of methane is about 4.5% for the stadials between DO events 18 and 20, which is in the same order as in the stadials before and after DO event 2 around the Last Glacial Maximum. The rIPD of methane remains relatively stable throughout the full last glacial, with a tendency for elevated values during interstadial compared to stadial periods.

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