Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation

AbstractContinuous, detailed isotope (δD and δ18O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984– 2000. In addition, snow samples taken along the 1km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. the stacked δD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, ~102 years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.

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A 60-year ice-core record of regional climate from Adélie Land, coastal Antarctica

The Cryosphere ◽

10.5194/tc-11-343-2017 ◽

2017 ◽

Vol 11 (1) ◽

pp. 343-362 ◽

Cited By ~ 11

Author(s):

Sentia Goursaud ◽

Valérie Masson-Delmotte ◽

Vincent Favier ◽

Susanne Preunkert ◽

Michel Fily ◽

...

Keyword(s):

High Resolution ◽

Sea Ice ◽

Interannual Variability ◽

Ice Core ◽

Ice Sheet ◽

Sea Ice Extent ◽

Antarctic Ice Sheet ◽

Ice Core Record ◽

Decadal Variations ◽

The Mean

Abstract. A 22.4 m-long shallow firn core was extracted during the 2006/2007 field season from coastal Adélie Land. Annual layer counting based on subannual analyses of δ18O and major chemical components was combined with 5 reference years associated with nuclear tests and non-retreat of summer sea ice to build the initial ice-core chronology (1946–2006), stressing uncertain counting for 8 years. We focus here on the resulting δ18O and accumulation records. With an average value of 21.8 ± 6.9 cm w.e. yr−1, local accumulation shows multi-decadal variations peaking in the 1980s, but no long-term trend. Similar results are obtained for δ18O, also characterised by a remarkably low and variable amplitude of the seasonal cycle. The ice-core records are compared with regional records of temperature, stake area accumulation measurements and variations in sea-ice extent, and outputs from two models nudged to ERA (European Reanalysis) atmospheric reanalyses: the high-resolution atmospheric general circulation model (AGCM), including stable water isotopes ECHAM5-wiso (European Centre Hamburg model), and the regional atmospheric model Modèle Atmosphérique Régional (AR). A significant linear correlation is identified between decadal variations in δ18O and regional temperature. No significant relationship appears with regional sea-ice extent. A weak and significant correlation appears with Dumont d'Urville wind speed, increasing after 1979. The model-data comparison highlights the inadequacy of ECHAM5-wiso simulations prior to 1979, possibly due to the lack of data assimilation to constrain atmospheric reanalyses. Systematic biases are identified in the ECHAM5-wiso simulation, such as an overestimation of the mean accumulation rate and its interannual variability, a strong cold bias and an underestimation of the mean δ18O value and its interannual variability. As a result, relationships between simulated δ18O and temperature are weaker than observed. Such systematic precipitation and temperature biases are not displayed by MAR, suggesting that the model resolution plays a key role along the Antarctic ice sheet coastal topography. Interannual variations in ECHAM5-wiso temperature and precipitation accurately capture signals from meteorological data and stake observations and are used to refine the initial ice-core chronology within 2 years. After this adjustment, remarkable positive (negative) δ18O anomalies are identified in the ice-core record and the ECHAM5-wiso simulation in 1986 and 2002 (1998–1999), respectively. Despite uncertainties associated with post-deposition processes and signal-to-noise issues, in one single coastal ice-core record, we conclude that the S1C1 core can correctly capture major annual anomalies in δ18O as well as multi-decadal variations. These findings highlight the importance of improving the network of coastal high-resolution ice-core records, and stress the skills and limitations of atmospheric models for accumulation and δ18O in coastal Antarctic areas. This is particularly important for the overall East Antarctic ice sheet mass balance.

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Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000009321 ◽

1989 ◽

Vol 35 (121) ◽

pp. 392-398 ◽

Cited By ~ 95

Author(s):

V.Ya. Lipenkov ◽

N.I. Barkov ◽

P. Duval ◽

P. Pimienta

Keyword(s):

Enhancement Factor ◽

Crystal Size ◽

Gradual Increase ◽

Ice Core ◽

Impurity Content ◽

Mean Value ◽

Axis Orientation ◽

Vostok Station ◽

The Mean ◽

Convergent Flow

AbstractCrystalline texture andc-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.Thec-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

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Crystalline Texture of the 2083 m Ice Core at Vostok Station, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000009321 ◽

1989 ◽

Vol 35 (121) ◽

pp. 392-398 ◽

Cited By ~ 2

Author(s):

V.Ya. Lipenkov ◽

N.I. Barkov ◽

P. Duval ◽

P. Pimienta

Keyword(s):

Enhancement Factor ◽

Crystal Size ◽

Gradual Increase ◽

Ice Core ◽

Impurity Content ◽

Mean Value ◽

Axis Orientation ◽

Vostok Station ◽

The Mean ◽

Convergent Flow

AbstractCrystalline texture and c-axis orientation of the 2083 m ice core at Vostok Station, covering more than 150kyear, reveal the existence of strong anisotropics. Changes in crystal size with depth are compatible with the growth of grains driven by the free energy of grain boundaries. A smaller growth rate appears to be associated with cold periods. A gradual increase in the horizontal elongation of grains was observed between 350 and 680 m. But, the mean value of the coefficient of the linear dimensional orientation of grains does not change below 700 m.The c-axis orientation of ice grains tends to orientate perpendicular to the direction of the elongation of grains, forming a vertical girdle pattern. This characteristic fabric has been interpreted as resulting from the gradual rotation of grains by basal glide under uniaxial longitudinal tension. The rotation of grains was calculated with respect to the total strain, simulating the formation of the girdle fabric pattern. The fabric-enhancement factor was calculated at various depths. It appears that Vostok ice hardens gradually with depth when considering the transverse convergent flow. No significant variation of the enhancement factor was observed with changes in climate and impurity content.

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Examining the strength of the link between surface temperature and surface mass balance in ice cores and models over the last centuries in Antarctica

10.5194/egusphere-egu2020-801 ◽

2020 ◽

Author(s):

Marie G. P. Cavitte ◽

Quentin Dalaiden ◽

Hugues Goosse ◽

Jan T.M. Lenaerts ◽

Elizabeth R. Thomas

Keyword(s):

Large Scale ◽

Ice Core ◽

Ice Sheets ◽

Ice Cores ◽

Regional Model ◽

Snow Accumulation ◽

Surface Mass Balance ◽

Weak Correlation ◽

Surface Mass ◽

The Past

Ice cores constitute an important record of the past surface mass balance (SMB) of the ice sheets, with SMB ultimately modulating the ice sheets&#8217; sea level impact. For the Antarctic Ice Sheet (AIS), SMB is dominated by snow accumulation and strongly controlled by atmospheric circulation. Large-scale atmospheric depressions collect warmth and moisture from further north that they then release over the AIS in the form of widespread accumulation or focused atmospheric rivers. This implies that snow deposited at the surface of the AIS should show strongly coupled SMB and surface air temperatures (SAT) variations. Ice cores do not record SAT directly but their d18O record is often used as a temperature proxy.&#160;Here, using the PAGES 2k Network ice core compilations of SMB and d18O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak correlation between SMB and d18O over historical timescales, and an equivalently weak correlation between SMB and SAT based on the Nicolas & Bromwich (2014) SAT reconstructions. However, we calculate a strong and positive SMB-SAT correlation in the majority of regions of the AIS using Global Climate Models (GCM) and the regional model RACMO2.3p2.&#160;To resolve the discrepancy between measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB-SAT correlation. This increase in measured SMB-SAT correlation likely results from noise present in the ice core records, but is not enough to match the strong correlation calculated in the models. On the model side, the high spatial resolution of the RACMO2.3p2 model allows us to highlight a number of areas of the AIS where SMB and SAT are not strongly correlated. We describe how wind-driven processes acting on the SMB and SAT locally, through Foehn and katabatic effects, can overwhelm the large-scale atmospheric input that induces the positive SMB-SAT correlations. In particular, we focus on Dronning Maud Land, East Antarctica, where each ice promontory clearly shows this wind-driven snow redistribution. Nevertheless, those regions displaying a low SMB-SAT correlation cover only a small fraction of the AIS and are not sufficient to explain the model-data discrepancy, suggesting a critical role of processes at a scale smaller than the one resolved by the regional model.&#160;References:Thomas, E. R., 2017, Regional Antarctic snow accumulation over the past 1000 years, Climate of the Past, 13, 1491&#8211;1513.Stenni, B. et al., 2017, Antarctic climate variability on regional and continental scales over the last 2000 years, Climate of the Past, 13, 1609&#8211;1634.Nicolas, J. P. & Bromwich, D. H., 2014, New reconstruction of Antarctic near-surface temperatures: Multidecadal trends and reliability of global reanalyses, Journal of Climate, 27, 8070&#8211;8093.

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Snow accumulation rate on Qomolangma (Mount Everest), Himalaya: synchroneity with sites across the Tibetan Plateau on 50–100 year timescales

Journal of Glaciology ◽

10.3189/002214308784886126 ◽

2008 ◽

Vol 54 (185) ◽

pp. 343-352 ◽

Cited By ~ 53

Author(s):

Susan Kaspari ◽

Roger LeB. Hooke ◽

Paul Andrew Mayewski ◽

Shichang Kang ◽

Shugui Hou ◽

...

Keyword(s):

Tibetan Plateau ◽

Accumulation Rate ◽

Ice Core ◽

Snow Accumulation ◽

The Tibetan Plateau ◽

Mount Everest ◽

Mountain Meteorology ◽

Annual Layer ◽

Decadal Scale ◽

The Mean

AbstractAnnual-layer thickness data, spanning AD 1534–2001, from an ice core from East Rongbuk Col on Qomolangma (Mount Everest, Himalaya) yield an age–depth profile that deviates systematically from a constant accumulation-rate analytical model. The profile clearly shows that the mean accumulation rate has changed every 50–100 years. A numerical model was developed to determine the magnitude of these multi-decadal-scale rates. The model was used to obtain a time series of annual accumulation. The mean annual accumulation rate decreased from ∼0.8 m ice equivalent in the 1500s to ∼0.3 m in the mid-1800s. From ∼1880 to ∼1970 the rate increased. However, it has decreased since ∼1970. Comparison with six other records from the Himalaya and the Tibetan Plateau shows that the changes in accumulation in East Rongbuk Col are broadly consistent with a regional pattern over much of the Plateau. This suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area. However, a record from Dasuopu, only 125 km northwest of Qomolangma and 700 m higher than East Rongbuk Col, shows a maximum in accumulation during the 1800s, a time during which the East Rongbuk Col and Tibetan Plateau ice-core and tree-ring records show a minimum. This asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology.

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Internal radio-echo layering at Vostok station, Antarctica, as an independent stratigraphie control on the ice-core record

Annals of Glaciology ◽

10.3189/1998aog27-1-360-364 ◽

1998 ◽

Vol 27 ◽

pp. 360-364 ◽

Cited By ~ 14

Author(s):

Martin J. Siegert ◽

Richard Hodgkinst ◽

Julian A. Dowdeswell

Keyword(s):

Ice Core ◽

Ice Sheet ◽

Ice Cores ◽

M Wave ◽

Geometric Spreading ◽

Volcanic Events ◽

Radio Echo Sounding ◽

Ice Core Record ◽

Vostok Station ◽

Station Site

Antarctic radio-echo sounding (RES) data at 60 MHz have been used to determine an independent stratigraphy for the ice core at Vostok station, based on internal radio-echo layering. A-scope RES data allow the amplitude of reflected electromagnetic (e/m) waves to be measured and, by accounting fur geometric spreading and absorption losses of the e/m wave, power reflection coefficients (PRCs) to be calculated. This information is compared with time-continuous Z-scope RES data in order to trace continuous e/m reflectors across the ice sheet. Internal ice-sheet horizons deeper than 800 m are caused by layers of ice that possess distinctly different dielectric properties (i.e. acidic layers) compared with ice above and/or below. Comparison of four PRC samples, located ~ 5 km from Vostok station, revealed five distinct internal reflections between 1000 and 2200 m. Z-scope data from directly over the Vostok station site show the same five prominent internal radio-echo layers. The depth-related radio-echo signals were then compared with chemical records from the Vostok ice core, including the H2SO4 signal, a major component of which is derived from volcanic events. From this procedure, internal radio-echo reflectors and Vostok ice-core acid measurements were correlated. Avery good match was made between Z-scope and ice-core data. However, vertical offsets observed between A-scope-derived RES layers and peaks in the chemical signal of up to 100 m are probably due to the general Inkling of the ice-sheet layering between the core site and the RES flight-line. We conclude that 60 MHz RES layering may be regarded as a stratigraphy independent of palaeoclimate, and may be used to correlate other deep Southern Hemisphere ice cores.

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Drought-induced biomass burning as a source of black carbon to the Central Himalaya since 1781 CE as reconstructed from the Dasuopu Ice Core

10.5194/acp-2020-1052 ◽

2020 ◽

Author(s):

Joel D. Barker ◽

Susan Kaspari ◽

Paolo Gabrielli ◽

Anna Wegner ◽

Emilie Beaudon ◽

...

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Monsoon Season ◽

Ice Core ◽

Snow Accumulation ◽

Back Trajectory ◽

Central Himalaya ◽

North West ◽

Ice Core Record ◽

Dasuopu Glacier

Abstract. Himalayan glaciers are melting due to atmospheric warming with the potential to limit access to water for more than 25 % of the global population that reside in these glacier meltwater catchments. Black carbon has been implicated as a factor that is contributing to Himalayan glacier melt, but its sources and mechanisms of delivery to the Himalayas remain controversial. Here, we provide a 211-year ice core record spanning 1781–1992 CE for refractory black carbon (rBC) deposition from the Dasuopu glacier ice core, that has to date provided the highest elevation ice core record (7200 m). We report an average rBC concentration of 1.5 µg/L (SD = 5.0, n = 1628) over the 211-year period. An increase in the frequency and magnitude of rBC deposition occurs after 1877 CE, accompanied by decreased snow accumulation associated with a shift in the North Atlantic Oscillation Index to a positive phase. Typically, rBC is deposited onto Dasuopu glacier during the non-monsoon season, and short-lived increases in rBC concentration are associated with periods of drought within neighboring regions in north-west India, Afghanistan and Pakistan. Using a combination of spectral and back trajectory analyses, and comparison with a concurrent analysis of trace metals at equivalent depths in the same ice core, we show that biomass burning resulting from dry conditions is a source of rBC to the central Himalaya, and is responsible for deposition that is up to 60 times higher than the average rBC concentration over the time period analyzed. We suggest that biomass burning is a significant source of rBC to the central Himalaya, and that the rBC record can be used to identify periods of drought in nearby regions that are up-wind of Dasuopu glacier.

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Drought-induced biomass burning as a source of black carbon to the central Himalaya since 1781 CE as reconstructed from the Dasuopu ice core

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-5615-2021 ◽

2021 ◽

Vol 21 (7) ◽

pp. 5615-5633

Author(s):

Joel D. Barker ◽

Susan Kaspari ◽

Paolo Gabrielli ◽

Anna Wegner ◽

Emilie Beaudon ◽

...

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Monsoon Season ◽

Ice Core ◽

Snow Accumulation ◽

Back Trajectory ◽

Central Himalaya ◽

The North ◽

Ice Core Record ◽

Dasuopu Glacier

Abstract. Himalayan glaciers are melting due to atmospheric warming, with the potential to limit access to water for more than 25 % of the global population that resides in these glacier meltwater catchments. Black carbon has been implicated as a factor that is contributing to Himalayan glacier melt, but its sources and mechanisms of delivery to the Himalayas remain controversial. Here, we provide a 211-year ice core record spanning 1781–1992 CE for refractory black carbon (rBC) deposition from the Dasuopu glacier ice core that has to date provided the highest-elevation ice core record (7200 m). We report an average rBC concentration of 1.5 µg L−1 (SD=5.0, n=1628) over the 211-year period. An increase in the frequency and magnitude of rBC deposition occurs after 1877 CE, accompanied by decreased snow accumulation associated with a shift in the North Atlantic Oscillation Index to a positive phase. Typically, rBC is deposited onto Dasuopu glacier during the non-monsoon season, and short-lived increases in rBC concentration are associated with periods of drought within neighboring regions in northwestern India, Afghanistan, and Pakistan. Using a combination of spectral and back-trajectory analyses, as well as a comparison with a concurrent analysis of trace metals at equivalent depths in the same ice core, we show that biomass burning resulting from dry conditions is a source of rBC to the central Himalaya and is responsible for deposition that is up to 60 times higher than the average rBC concentration over the time period analyzed. We suggest that biomass burning is a significant source of rBC to the central Himalaya and that the rBC record can be used to identify periods of drought in nearby regions that are upwind of Dasuopu glacier.

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Air-hydrate crystals in deep ice-core samples from Vostok Station, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000003828 ◽

1994 ◽

Vol 40 (134) ◽

pp. 79-86 ◽

Cited By ~ 49

Author(s):

T. Uchida ◽

T. Hondoh ◽

S. Mae ◽

V.YA. Lipenkov ◽

P. Duval

Keyword(s):

Volume Concentration ◽

Ice Core ◽

Site Occupancy ◽

Mean Value ◽

Gas Content ◽

Glacial Ice ◽

Core Samples ◽

Vostok Station ◽

The Mean ◽

Geometrical Equation

AbstractMicroscopic observation of air-hydrate crystals was carried out using 34 deep ice-core samples retrieved at Vostok Station, Antarctica. Samples were obtained from depths between 1050 and 2542 m, which correspond to Wisconsin/Sangamon/Illinoian ice. It was found that the volume and number of air-hydrate varied with the climatic changes. The volume concentration of air-hydrate in the interglacial ice was about 30% larger than that in the glacial ice. In the interglacial ice, the number concentration of air-hydrate was about a half and the mean volume of air-hydrate was nearly three times larger than that in the glacial-age ice. The air-hydrate crystals were found to grow in the ice sheet, about 6.7 × 10−12cm3year-1, in compensation for the disappearance of smaller ones. The volume concentration of air-hydrate was related to the total gas content by a geometrical equation with a proportional parameter α. The mean value of α below 1250 m, where no air bubbles were found, was about 0.79. This coincided with an experimentally determined value of the crystalline site occupancy of the air-hydrate in a 1500 m core obtained at Dye 3, Greenland (Hondoh and others, 1990). In the depth profile of calculated α for many samples, α in the interglacial ice was about 30% smaller than that in the glacial-age ice.

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Ice Structure and Crystal Fabrics of the 2200 M Ice Core at Vostok Station, Antarctica

Annals of Glaciology ◽

10.3189/s0260305500004705 ◽

1988 ◽

Vol 10 ◽

pp. 223-223

Author(s):

N.I. Barkov ◽

V.Ya. Lipenkov ◽

V.N. Petrov

Keyword(s):

Ice Core ◽

Three Dimensional ◽

Air Bubbles ◽

The Core ◽

Polycrystalline Ice ◽

Vostok Station ◽

Dimensional Parameters ◽

The Mean ◽

Ice Fabrics

Both the ice structure and the ice fabric along the 2200 m ice core at Vostok Station were investigated during the 25th, 29th and 30th Soviet Antarctic Expeditions.Several kinds of three-dimensional parameters of polycrystalline ice were measured, e.g. the mean diameter and size distribution of ice crystals and air bubbles, and specific volumeThe variation in most of these parameters along the core reflects not only the process of metamorphism in ice but also changes in the environmental conditions at the surface. The causes of these variations are discussed, in order to estimate the possibility of a paleoclimatic interpretation.The evolution of c-axis fabrics with depth is discussed in relation to the ice-deformation conditions.A comparison of ice fabrics at Vostok, Byrd Station and Camp Century shows that similar mechanisms cause the reorientation of crystals. The role of temperature in fabric development is discussed.

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