Post-depositional movement of methanesulphonic acid at Law Dome, Antarctica, and the influence of accumulation rate

AbstractA series of ice cores from sites with different snow-accumulation rates across Law Dome, East Antarctica, was investigated for methanesulphonic acid (MSA) movement. the precipitation at these sites (up to 35 km apart) is influenced by the same air masses, the principal difference being the accumulation rate. At the low-accumulation-rate W20k site (0.17m ice equivalent), MSAwas completely relocated from the summer to winter layer. Moderate movement was observed at the intermediate-accumulation-rate site (0.7m ice equivalent), Dome Summit South (DSS), while there was no evidence of movement at the high-accumulation-rate DE08 site (1.4m ice equivalent). the main DSS record of MSA covered the epoch AD 1727–2000 and was used to investigate temporal post-depositional changes. Co-deposition of MSA and sea-salt ions was observed in the surface layers, outside of the main summer MSA peak,which complicates interpretation of these peaks as evidence of movement in deeper layers. A seasonal study of the 273 year DSS record revealed MSA migration predominantly from summer into autumn (in the up-core direction), but this migration was suppressed during the Tambora (1815) and unknown (1809) volcanic eruption period, and enhanced during an epoch (1770–1800) with high summer nitrate levels. A complex interaction between the gradients in nss-sulphate, nitrate and sea salts (which are influenced by accumulation rate) is believed to control the rate and extent of movement of MSA.

Download Full-text

Enhanced Moisture Delivery into Victoria Land, East Antarctica During the Early Last Interglacial: Implications for West Antarctic Ice Sheet Stability

10.5194/cp-2021-7 ◽

2021 ◽

Author(s):

Yuzhen Yan ◽

Nicole E. Spaulding ◽

Michael L. Bender ◽

Edward J. Brook ◽

John A. Higgins ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Cores ◽

Snow Accumulation ◽

East Antarctica ◽

Ice Age ◽

Accumulation Rates ◽

Last Interglacial ◽

Ice Shelf ◽

Ross Ice Shelf ◽

Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in Southern Victoria Land ~80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 and 116 thousand years before present (ka) to infer moisture transport into the region. The accumulation rate is based on the ice age-gas age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields a six-fold increase in the accumulation rate in the LIG, whereas other Antarctic ice cores are typically characterized by a glacial-interglacial difference of a factor of two to three. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size, and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

Download Full-text

Snow-Pit Record from a Coastal Antarctic Site and Its Preservation of Meteorological Features

Earth Interactions ◽

10.1175/ei-d-20-0018.1 ◽

2021 ◽

Vol 25 (1) ◽

pp. 108-118

Author(s):

Yalalt Nyamgerel ◽

Sang-Bum Hong ◽

Yeongcheol Han ◽

Songyi Kim ◽

Jeonghoon Lee ◽

...

Keyword(s):

Sea Ice ◽

Air Temperature ◽

Ice Cores ◽

Snow Accumulation ◽

Sea Salt ◽

Temperature Record ◽

Sea Ice Extent ◽

Environmental Signals ◽

Salt Ions ◽

Polar Snow

Abstract Polar snow pits or ice cores preserve valuable information derived from the atmosphere on past climate and environment changes. A 1.57-m snow-pit record from the coastal site (Styx Glacier) in eastern Antarctica covering the period from January 2011 to January 2015 was discussed and compared with meteorological variables. The dominant contribution of the deposition of sea-salt aerosols due to the proximity of the site to the ocean and processes of sea ice formation was revealed in the ionic concentrations. Consistent seasonal peaks in δ 18 O, δ D, MSA, , and indicate the strong enhancement of their source during warm periods, whereas the sea-salt ions (Na + , K + , Mg 2+ , Ca 2+ , Cl − , and ) exhibit a distinct distribution. Monthly mean δ 18 O positively correlates with the air temperature record from an automatic weather station (AWS) located in the main wind direction. Despite the shortness of the record, we suspect that the slight depletion of the isotopic composition and lowering of the snow accumulation could be related to the cooler air temperature with the decrease of open sea area. Consistency with previous studies and the positive correlation of sea-salt ions in the snow pit indicate the relatively good preservation of snow layers with noticeable climate and environmental signals [e.g., changes in sea ice extent (SIE) or sea surface temperature]. We report a new snow-pit record, which would be comparative and supportive to understand similar signals preserved in deeper ice cores in this location.

Download Full-text

Snow-accumulation rates and isotopic content (2H,3H) of near-surface firn from the Filchner-Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500016335 ◽

1994 ◽

Vol 20 ◽

pp. 121-128 ◽

Cited By ~ 1

Author(s):

W. Graf ◽

H. Moser ◽

O. Reinwarth ◽

J. Kipfstuhl ◽

H. Oerter ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Cores ◽

Snow Accumulation ◽

Accumulation Rates ◽

Ice Shelf ◽

Near Surface ◽

Surface Data ◽

Chemical Profiles ◽

Ice Edge ◽

The Antarctic

The accumulation and distribution of the2H content of near-surface layers in the eastern part of the Ronne Ice Shelf were determined from 16 firn cores drilled to about 10 m depth during the Filchner IIIa and IV campaigns in 1990 and 1992, respectively. The cores were dated stratigraphically by seasonal δ2H variations in the firn. In addition,3H and high-resolution chemical profiles were used to assist in dating. Both the accumulation rate and the stable-isotope content decrease with increasing distance from the ice edge: the δ2H values range from about 195‰ at the ice edge to -25‰ at BAS sites 5 and 6, south of Henry Ice Rise, and the accumulation rates from about 210 to 90 kgm-2a-1. The δ2H values of the near-surface firn and the 10 m firn temperatures (Θ) at individual sites are very well correlated: dδ2H/dΘ = (10.3 ± 0.6)‰K-1; r = 0.97.The δ2H profiles of the two ice cores BI3 and BI5 drilled in 1990 and 1992 to 215 and 320 m depth, respectively, reflect the gradual depletion in2H in the firn upstream of the drill sites. Comparison with the surface data indicates that the ice above 142 m in core BIS and above 137 m in core BI3 was deposited on the ice shelf, whereas the deeper ice, down to 152.8 m depth, most probably originated from the margin of the Antarctic ice sheet.

Download Full-text

Topographic control of regional accumulation rate variability at South Pole and implications for ice-core interpretation

Annals of Glaciology ◽

10.3189/172756404781814050 ◽

2004 ◽

Vol 39 ◽

pp. 214-218 ◽

Cited By ~ 23

Author(s):

Gordon S. Hamilton

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Ice Sheet ◽

Ice Cores ◽

Snow Accumulation ◽

Topographic Effects ◽

South Pole ◽

Accumulation Rates ◽

Surface Slope ◽

Ice Dynamics

AbstractSnow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is ∼18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals.

Download Full-text

Snow accumulation rate and atmospheric oxidation pathway proxies from nitrate isotopes in East Antarctica

10.5194/egusphere-egu2020-9109 ◽

2020 ◽

Author(s):

Pete Akers ◽

Joël Savarino ◽

Nicolas Caillon

Keyword(s):

Oxygen Isotope ◽

Accumulation Rate ◽

Isotopic Fractionation ◽

Ice Cores ◽

Snow Accumulation ◽

East Antarctica ◽

Atmospheric Oxidation ◽

High Accumulation ◽

Antarctic Snow ◽

History Of

<p>Nitrate is naturally deposited in Antarctic snow and is detectable at low concentrations throughout our deepest ice cores. However, nitrate is photoreactive under ultraviolet light and experiences significant post-depositional loss. This nitrate loss favors 14NO3- over 15NO3-, and the resulting isotopic fractionation can be used as a proxy for duration of sunlight exposure. Here, we present nitrate isotope data (&#948;15N, &#948;18O, &#916;17O) sampled from shallow snow cores and pits across East Antarctica. Our >30 sampling sites extend from coastal Ad&#233;lie Land onto the high East Antarctic Plateau at Dome C and beyond, covering annual snow mass balances that range from 240 mm/yr to less than 30 mm/yr (water equivalent). The &#948;15N of nitrate at these sites show an inverse relationship with snow accumulation rate, with &#948;15N &#8776; 20&#8240; at the coastal sites with the highest accumulations and &#948;15N &#8776; 150-250&#8240; at the driest inland sites. This relationship develops because newly deposited nitrate is buried below the level of light penetration by new snow relatively quickly at high accumulation sites, but nitrate at drier sites can be exposed to sunlight for several years. After burial below the reach of sunlight, the &#948;15N signature of nitrate is preserved and thus offers a new proxy for snow accumulation rate in East Antarctic ice cores. In contrast, the oxygen isotopes of nitrate isotopically exchange with surrounding ice after burial, which complicates their interpretation. However, our large sample set allows an estimation of the rate of isotopic exchange at various sites, and the original isotopic values at the time of deposition may be approximated after correcting for this rate of exchange. These oxygen isotope values likely reflect in part the atmospheric oxidation history of the nitrate and its nitrogen oxide progenitor, but further study is needed to fully understand nitrate oxygen isotope dynamics.</p>

Download Full-text

Snow accumulation rates in northern Victoria Land, Antarctica, by firn-core analysis

Journal of Glaciology ◽

10.3189/172756500781832774 ◽

2000 ◽

Vol 46 (155) ◽

pp. 541-552 ◽

Cited By ~ 39

Author(s):

Barbara Stenni ◽

Francesca Serra ◽

Massimo Frezzotti ◽

Valter Maggi ◽

Rita Traversi ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Cores ◽

Snow Accumulation ◽

Katabatic Wind ◽

Climatic Data ◽

Accumulation Rates ◽

Surface Mass ◽

Physical Study ◽

Victoria Land ◽

The Mean

AbstractA multiparametric (chemical, isotopic and physical) study on three shallow firn cores sampled in northern Victoria Land was carried out to obtain glaciological information and climatic data in this Antarctic region. Sampling areas were accurately prospected to identify sites, located at different altitudes and distances from the sea, where the snow accumulation was not influenced by katabatic wind redistribution or summer melting. Stratigraphic, isotopic (δl8O) and chemical (H2O2, MSA and nssSO42−) profiles were mutually examined for dating purposes and to determine the mean snow-accumulation rates at three different stations. Annual accumulation rates of 85–420 kg m−2 a−1 were determined in the period 1971–92. An inverse pattern between accumulation rate and altitude was shown by the progression of the mean annual rates of 160, 203 and 260 kg m−2 a−1, respectively, in the highest, medium and lowest stations. The mean accumulation value of all northern Victoria Land data available, 170 kg m−2 a−1, represents a decrease of up to 35% with respect to the estimated value most widely used until now. Our accumulation value is very close to that required for a zero net surface mass balance according to ice discharge. A linear relationship with a gradient of 0.81‰ °C−1 has been found between mean δ18O values and mean annual surface temperature for different ice cores drilled in northern Victoria Land.

Download Full-text

A 485 year record of atmospheric chloride, nitrate and sulfate: results of chemical analysis of ice cores from Dyer Plateau, Antarctic Peninsula

Annals of Glaciology ◽

10.3189/s0260305500015792 ◽

1995 ◽

Vol 21 ◽

pp. 182-188 ◽

Cited By ~ 5

Author(s):

Jihong Cole Dai ◽

Lonnie G. Thompson ◽

Ellen Mosley-Thompson

Keyword(s):

Sea Water ◽

Accumulation Rate ◽

Linear Regression Analysis ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

Sea Salt ◽

Volcanic Emissions ◽

Data Set ◽

Snow Chemistry

Detailed ionic analyses of Dyer Plateau snow show that major soluble impurities in snow consist of sodium (Na+), chloride (Cl−), nitrate (NO3−), sulfate (SO42−), and acidity (H+). The ratios of Na+ to Cl− concentrations are close to that of sea water, indicating little or no fractionation of sea-salt aerosols. The analyses of core sections from three sites along a 10 km transect show that local spatial variation of snow chemistry in this area is minimal and that temporal (decadal, inter-annual and sub-annual) variations in snow chemistry are very well preserved.Anion analyses of the upper 181 m section of two 235 m ice cores yield a data set of 485 years (1505-1989) of annual snow accumulation and fluxes of Cl−, NO3−, and non-sea-salt (nss) SO42−. No significant long-term trends are observed in any of the anion fluxes. This is consistent with other Antarctic ice-core records showing no significant anthropogenic atmospheric pollution in the high southern latitudes. Linear regression analysis shows that Cl− flux is independent of snow-accumulation rate. Significant positive correlations are found between accumulation rate and both NO3− flux and background nss-SO42− flux. These results suggest that dry deposition is primarily responsible for air-to-ground Cl− flux while wet deposition dominates the NO3− and nss-SO42− flux (≥90% and ≥75%, respectively). The nss-S042− fluxes provide a chronology of explosive volcanic emissions reaching the Antarctic region for the past 485 years.

Download Full-text

Spatial and temporal variability of snow accumulation using ground-penetrating radar and ice cores on a Svalbard glacier

Journal of Glaciology ◽

10.3189/172756502781831205 ◽

2002 ◽

Vol 48 (162) ◽

pp. 417-424 ◽

Cited By ~ 58

Author(s):

Anja Pälli ◽

Jack C. Kohler ◽

Elisabeth Isaksson ◽

John C. Moore ◽

Jean Francis Pinglot ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

Spatial And Temporal Variability ◽

Accumulation Rates ◽

Radar Reflection ◽

Ground Penetrating ◽

Horizontal Layers

AbstractA 50 MHz ground-penetrating radar was used to detect horizontal layers in the snowpack along a longitudinal profile on Nordenskjöldbreen, a Svalbard glacier. The profile passed two shallow and one deep ice-core sites. Two internal radar reflection layers were dated using parameters measured in the deep core. Radar travel times were converted to water equivalent, yielding snow-accumulation rates along the profile for three time periods: 1986–99, 1963–99 and 1963–86. The results show 40–60% spatial variability in snow accumulation over short distances along the profile. The average annual accumulation rate for 1986–99 was found to be about 12% higher than for the period 1963–86, which indicates increased accumulation in the late 1980s and 1990s.

Download Full-text

Stratigraphic analysis of Dome Fuji Antarctic ice core using an optical scanner

Annals of Glaciology ◽

10.3189/172756404781813899 ◽

2004 ◽

Vol 39 ◽

pp. 467-472 ◽

Cited By ~ 13

Author(s):

Morimasa Takata ◽

Yoshinori Iizuka ◽

Takeo Hondoh ◽

Shuji Fujita ◽

Yoshiyuki Fujii ◽

...

Keyword(s):

Accumulation Rate ◽

Scattered Light ◽

Ice Core ◽

Ice Cores ◽

Core Sample ◽

Snow Accumulation ◽

Accumulation Rates ◽

Scanning Method ◽

Scattering Intensity ◽

Optical Scanner

AbstractLong-term changes of snow-accumulation rate in Antarctica are a major uncertainty in our understanding of past climate. Because the visible strata in polar ice are due to variations in the sizes and concentrations of air inclusions and microparticles, the scattered light intensity from an ice core yields valuable information on the stratification, which is likely to provide estimates of the annual accumulation rates. Identification of each layer is therefore necessary, and we developed an optical scanner apparatus to record detailed visible strata of ice cores. The apparatus records the two-dimensional distribution of light-scattering intensity along ice-core samples and produces an image of the whole ice-core sample by an image analysis process. These images showed that ice from Dome Fuji ice core contained a large number of layers. Volcanic layers were also well identified. We processed the scattering intensity on the enhanced intensity images to produce an intensity profile. This profile showed that the period of the intensity variations is consistent with a core-dating model applied to the Dome Fuji ice core. We also found that the intensity peaks are closely correlated to peaks in Ca2+ ion concentrations. Thus, our scanning method is a promising approach to measuring annual-layer thickness and, as a result, may be used to infer past accumulation rates in Antarctica.

Download Full-text

Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis

The Cryosphere ◽

10.5194/tc-12-1831-2018 ◽

2018 ◽

Vol 12 (5) ◽

pp. 1831-1850 ◽

Cited By ~ 2

Author(s):

Emmanuel Le Meur ◽

Olivier Magand ◽

Laurent Arnaud ◽

Michel Fily ◽

Massimo Frezzotti ◽

...

Keyword(s):

Error Analysis ◽

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

Time Averaging ◽

Accumulation Rates ◽

Accumulation Pattern ◽

Surface Mass ◽

First Results

Abstract. Results from ground-penetrating radar (GPR) measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC) and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last 600 years. Accurate dating of these internal reflection horizons (IRHs) is obtained from a depth–age relationship derived from volcanic horizons and bomb testing fallouts on a DC ice core and shows a very good consistency when tested against extra ice cores drilled along the radar profile. Accumulation rates are then inferred by accounting for density profiles down to each IRH. For the latter purpose, a careful error analysis showed that using a single and more accurate density profile along a DC core provided more reliable results than trying to include the potential spatial variability in density from extra (but less accurate) ice cores distributed along the profile. The most striking feature is an accumulation pattern that remains constant through time with persistent gradients such as a marked decrease from 26 mm w.e. yr−1 at DC to 20 mm w.e. yr−1 at the south-west end of the profile over the last 234 years on average (with a similar decrease from 25 to 19 mm w.e. yr−1 over the last 592 years). As for the time dependency, despite an overall consistency with similar measurements carried out along the main East Antarctic divides, interpreting possible trends remains difficult. Indeed, error bars in our measurements are still too large to unambiguously infer an apparent time increase in accumulation rate. For the proposed absolute values, maximum margins of error are in the range 4 mm w.e. yr−1 (last 234 years) to 2 mm w.e. yr−1 (last 592 years), a decrease with depth mainly resulting from the time-averaging when computing accumulation rates.

Download Full-text