Chemistry of snow and ice cores along the ice flow lines at Lake Vostok (Antarctica)

Abstract. The Northeast Greenland Ice Stream (NEGIS) is the largest active ice stream on the Greenland Ice Sheet (GrIS) and a crucial contributor to the ice-sheet mass balance. To investigate the ice-stream dynamics and to gain information about the past climate, a deep ice core is drilled in the upstream part of the NEGIS, termed the East Greenland Ice-core Project (EastGRIP). Upstream flow can introduce climatic bias into ice cores through the advection of ice deposited under different conditions further upstream. This is particularly true for EastGRIP due to its location inside an ice stream on the eastern flank of the GrIS. Understanding and ultimately correcting for such effects requires information on the atmospheric conditions at the time and location of snow deposition. We use a two-dimensional Dansgaard–Johnsen model to simulate ice flow along three approximated flow lines between the summit of the ice sheet (GRIP) and EastGRIP. Isochrones are traced in radio-echo-sounding images along these flow lines and dated with the GRIP and EastGRIP ice-core chronologies. The observed depth–age relationship constrains the Monte Carlo method which is used to determine unknown model parameters. We calculate backward-in-time particle trajectories to determine the source location of ice found in the EastGRIP ice core and present estimates of surface elevation and past accumulation rates at the deposition site. Our results indicate that increased snow accumulation with increasing upstream distance is predominantly responsible for the constant annual layer thicknesses observed in the upper part of the ice column at EastGRIP, and the inverted model parameters suggest that basal melting and sliding are important factors determining ice flow in the NEGIS. The results of this study form a basis for applying upstream corrections to a variety of ice-core measurements, and the inverted model parameters are useful constraints for more sophisticated modelling approaches in the future.

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Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

Climate of the Past ◽

10.5194/cp-11-1395-2015 ◽

2015 ◽

Vol 11 (10) ◽

pp. 1395-1416 ◽

Cited By ~ 13

Author(s):

S. Fujita ◽

F. Parrenin ◽

M. Severi ◽

H. Motoyama ◽

E. W. Wolff

Keyword(s):

Age Differences ◽

Flow Model ◽

Ice Cores ◽

Ice Flow ◽

Surface Mass ◽

The Past ◽

The One ◽

Mis 5E ◽

Age Constraints ◽

Mis 5

Abstract. Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

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Trace-Acid Ion Content of Shallow Snow and Ice Cores from Mountain Sites in Western Canada

Annals of Glaciology ◽

10.1017/s0260305500004171 ◽

1988 ◽

Vol 10 ◽

pp. 57-62 ◽

Cited By ~ 12

Author(s):

G. Holdsworth ◽

H.R. Krouse ◽

E. Peake

Keyword(s):

British Columbia ◽

Time Series ◽

Forest Fires ◽

Time Series Data ◽

Accumulation Rate ◽

Ice Cores ◽

Historical Record ◽

Yukon Territory ◽

Series Data ◽

Snow And Ice

An historical record of the deposition of common acids is contained in snow and ice cores taken from suitable sites in the accumulation zone of certain glaciers. Spatial and time-series data sets for trace-mineral acids have been obtained from snow-pit samples and ice cores from a number of mountain sites in Alberta, British Columbia, and the Northwest and Yukon Territories. In Alberta, it is possible to use temperate firn sites above 3460 m, although elution occurs during certain summers as indicated by isotopic and ionic data. This would also apply to sites of a similar latitude (52°±2°N) in British Columbia. In the Yukon Territory (≥60.5°N) reliable time series for the acid anions may be obtained from sites at altitudes above 3000 m. Elution provides a natural control for demonstrating that field sampling and subsequent analytical procedures do not introduce significant contamination. The Yukon data are compared with the net annual accumulation rate and with altitude. Recent data from the 5340 m Mt Logan site do not indicate any significant increase in natural background levels of snow acidity. Lightning, which is responsible for numerous forest fires in all provinces, is a possible natural source of nitric acid. Spring-summer peaks in nitrate concentration usually occur. In addition, forest-fire smoke may be a significant contributor to the mountain snow-pack chemistry in some years and must be considered when interpreting the Mt Logan core data. One Yukon profile seems to contain the signature from the 1986 Augustine volcanic eruption.

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Characterizing the glaciological conditions at Halvfarryggen ice dome, Dronning Maud Land, Antarctica

Journal of Glaciology ◽

10.3189/2013jog12j134 ◽

2013 ◽

Vol 59 (213) ◽

pp. 9-20 ◽

Cited By ~ 27

Author(s):

Reinhard Drews ◽

Carlos Martín ◽

Daniel Steinhage ◽

Olaf Eisen

Keyword(s):

Flow Model ◽

Ice Core ◽

Ice Cores ◽

Radar Data ◽

Ice Thickness ◽

Atmospheric Conditions ◽

Ice Flow ◽

International Partnerships ◽

Drill Site ◽

Dronning Maud Land

AbstractWe present a comprehensive approach (including field data, remote sensing and an anisotropic ice-flow model) to characterize Halvfarryggen ice dome in coastal Dronning Maud Land, Antarctica. This is a potential drill site for the International Partnerships in Ice Core Sciences, which has identified the need for ice cores covering atmospheric conditions during the last few millennia. We derive the surface topography, the ice stratigraphy from radar data, and accumulation rates which vary from 400 to 1670 kg m−2 a−1 due to preferred wind directions and changing surface slope. The stratigraphy shows anticlines and synclines beneath the divides. We transfer Dansgaard–Johnsen age–depth scales from the flanks along isochrones to the divide in the upper 20–50% of the ice thickness and show that they compare well with the results of a full-Stokes, anisotropic ice-flow model which predicts (1) 11 ka BP ice at 90% of the ice thickness, (2) a temporally stable divide for at least 2700–4500 years, (3) basal temperatures below the melting point (−12°C to −5°C) and (4) a highly developed crystal orientation fabric (COF). We suggest drilling into the apices of the deep anticlines, providing a good compromise between record length and temporal resolution and also facilitating studies of the interplay of anisotropic COF and ice flow.

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An overview of the studies on black carbon and mineral dust deposition in snow and ice cores in East Asia

Journal of Meteorological Research ◽

10.1007/s13351-014-4005-7 ◽

2014 ◽

Vol 28 (3) ◽

pp. 354-370 ◽

Cited By ~ 22

Author(s):

Xin Wang ◽

Baiqing Xu ◽

Jing Ming

Keyword(s):

East Asia ◽

Black Carbon ◽

Mineral Dust ◽

Ice Cores ◽

Dust Deposition ◽

Snow And Ice

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Spatial gradients of temperature, accumulation and δ<sup>18</sup>O-ice in Greenland over a series of Dansgaard–Oeschger events

Climate of the Past ◽

10.5194/cp-9-1029-2013 ◽

2013 ◽

Vol 9 (3) ◽

pp. 1029-1051 ◽

Cited By ~ 48

Author(s):

M. Guillevic ◽

L. Bazin ◽

A. Landais ◽

P. Kindler ◽

A. Orsi ◽

...

Keyword(s):

Flow Model ◽

Ice Cores ◽

Ice Age ◽

Age Difference ◽

Sea Ice Extent ◽

Ice Flow ◽

Spatial Gradients ◽

Climate Simulations ◽

Precipitation Seasonality ◽

Water Stable Isotope

Abstract. Air and water stable isotope measurements from four Greenland deep ice cores (GRIP, GISP2, NGRIP and NEEM) are investigated over a series of Dansgaard–Oeschger events (DO 8, 9 and 10), which are representative of glacial millennial scale variability. Combined with firn modeling, air isotope data allow us to quantify abrupt temperature increases for each drill site (1σ = 0.6 °C for NEEM, GRIP and GISP2, 1.5 °C for NGRIP). Our data show that the magnitude of stadial–interstadial temperature increase is up to 2 °C larger in central and North Greenland than in northwest Greenland: i.e., for DO 8, a magnitude of +8.8 °C is inferred, which is significantly smaller than the +11.1 °C inferred at GISP2. The same spatial pattern is seen for accumulation increases. This pattern is coherent with climate simulations in response to reduced sea-ice extent in the Nordic seas. The temporal water isotope (δ18O)–temperature relationship varies between 0.3 and 0.6 (±0.08) ‰ °C−1 and is systematically larger at NEEM, possibly due to limited changes in precipitation seasonality compared to GISP2, GRIP or NGRIP. The gas age−ice age difference of warming events represented in water and air isotopes can only be modeled when assuming a 26% (NGRIP) to 40% (GRIP) lower accumulation than that derived from a Dansgaard–Johnsen ice flow model.

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Ice flow field over Lake Vostok, East Antarctica inferred by structure tracking

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2004.09.021 ◽

2004 ◽

Vol 227 (3-4) ◽

pp. 249-261 ◽

Cited By ~ 28

Author(s):

Anahita A. Tikku ◽

Robin E. Bell ◽

Michael Studinger ◽

Garry K.C. Clarke

Keyword(s):

Flow Field ◽

East Antarctica ◽

Ice Flow ◽

Lake Vostok

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Historical reconstruction of the earth's past atmospheric environment from Greenland and Antarctic snow and ice cores

Environmental Reviews ◽

10.1139/a95-001 ◽

1995 ◽

Vol 3 (1) ◽

pp. 1-28 ◽

Cited By ~ 46

Author(s):

Claude F. Boutron

Keyword(s):

Heavy Metals ◽

Greenhouse Gases ◽

Industrial Revolution ◽

Ice Cores ◽

Atmospheric Environment ◽

Ice Caps ◽

The Past ◽

Antarctic Snow ◽

The Impact ◽

Snow And Ice

During the past decades, the investigation of various elements, species, and isotopes in the frozen atmospheric archives stored in the Greenland and Antarctic ice caps for several hundred thousand years has provided a wealth of fascinating information on past and recent changes in the atmospheric environment of our planet. After a brief description of the Antarctic and Greenland ice caps, we give an overview of the procedures that are used in the field for collecting snow and ice from the surface down to great depths. We discuss the techniques used to date and analyse the samples. The main results obtained to date are then presented, with special emphasis on the very recent. The analysis of the snow and ice layers deposited during the past few centuries, especially since the Industrial Revolution, has allowed us to assess clearly the impact human activity has had on the atmosphere, for important constituents such as heavy metals, sulfur and nitrogen compounds, greenhouse gases, carbon and organic compounds, and artificial radionuclides. The analysis of ancient ice up to several hundred thousand years old has provided unique insight on the past natural changes that affected our atmosphere during glacial–interglacial transitions, especially the temperature, greenhouse gases, soil- and sea-derived aerosols, and heavy metals.Key words: Greenland, Antarctica, ice, global pollution, climate change, heavy metals.

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Change of the ice rheology with climatic transitions – implication on ice flow modelling and dating of the EPICA Dome C core

Climate of the Past Discussions ◽

10.5194/cpd-2-1187-2006 ◽

2006 ◽

Vol 2 (6) ◽

pp. 1187-1219 ◽

Cited By ~ 1

Author(s):

G. Durand ◽

F. Gillet-Chaulet ◽

A. Svensson ◽

O. Gagliardini ◽

S. Kipfstuhl ◽

...

Keyword(s):

Flow Model ◽

Ice Core ◽

Ice Sheets ◽

Ice Cores ◽

Horizontal Shear ◽

Ice Flow ◽

Flow Modelling ◽

The Past ◽

Ice Flows ◽

Crystallographic Orientations

Abstract. The study of the distribution of the crystallographic orientations (the fabric) along ice cores supplies information on the past and current ice flows of ice-sheets. Beside the usually observed formation of a vertical single maximum fabric, the EPICA Dome Concordia ice core (EDC) shows an abrupt and unexpected strenghtening of its fabric during termination II around 1750 m depth. Such strengthenings were already observed for sites located on an ice-sheet. This suggests that horizontal shear could occur along the EDC core. Moreover, the change in the fabric leads to a modification of the viscosity between neighbouring ice layers. Through the use of an anisotropic ice flow model, we quantify the change in viscosity and investigate its implication on ice flow and dating.

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