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

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.

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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.

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Variability in accumulation rates from GPR profiling on the West Antarctic plateau

Annals of Glaciology ◽

10.3189/172756404781814393 ◽

2004 ◽

Vol 39 ◽

pp. 238-244 ◽

Cited By ~ 71

Author(s):

Vandy B. Spikes ◽

Gordon S. Hamilton ◽

Steven A. Arcone ◽

Susan Kaspari ◽

Paul A. Mayewski

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Track Length ◽

Flow Profile ◽

Accumulation Rates ◽

West Antarctica ◽

West Antarctic ◽

Ground Penetrating ◽

Along Track

AbstractIsochronal layers in firn detected with ground-penetrating radar (GPR) and dated using results from ice-core analyses are used to calculate accumulation rates along a 100 km across-flow profile in West Antarctica. Accumulation rates are shown to be highly variable over short distances. Elevation measurements from global positioning system surveys show that accumulation rates derived from shallow horizons correlate well with surface undulations, which implies that wind redistribution of snow is the leading cause of this variability. Temporal changes in accumulation rate over 25–185 year intervals are smoothed to along-track length scales comparable to surface undulations in order to identify trends in accumulation that are likely related to changes in climate. Results show that accumulation rates along this profile have decreased in recent decades, which is consistent with core-derived time series of annual accumulation rates measured at the two ends of the radar profile. These results suggest that temporal variability observed in accumulation-rate records from ice cores and GPR profiles can be obscured by spatial influences, although it is possible to resolve temporal signals if the effects of local topography and ice flow are quantified and removed.

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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.

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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.

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Reconstructing Antarctic snow accumulation using nitrogen isotopes of nitrate

10.5194/egusphere-egu21-672 ◽

2021 ◽

Author(s):

Pete D. Akers ◽

Joël Savarino ◽

Nicolas Caillon ◽

Mark Curran ◽

Tas Van Ommen

Keyword(s):

Nitrogen Isotopes ◽

Full Range ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

East Antarctica ◽

Accumulation Rates ◽

Sea Levels ◽

Antarctic Snow ◽

Parallel Reconstruction

Precise Antarctic snow accumulation estimates are needed to understand past and future changes in global sea levels, but standard reconstructions using water isotopes suffer from competing isotopic effects external to accumulation. We present here an alternative accumulation proxy based on the post-depositional photolytic fractionation of nitrogen isotopes (d15N) in nitrate. On the high plateau of East Antarctica, sunlight penetrating the uppermost snow layers converts snow-borne nitrate into nitrogen oxide gas that can be lost to the atmosphere. This nitrate loss favors 14NO3- over 15NO3-, and thus the d15N of nitrate remaining in the snow will steadily increase until the nitrate is eventually buried beneath the reach of light. Because the duration of time until burial is dependent upon the rate of net snow accumulation, sites with lower accumulation rates have a longer burial wait and thus higher d15N values. A linear relationship (r2 = 0.86) between d15N and net accumulation-1 is calculated from over 120 samples representing 105 sites spanning East Antarctica. These sites largely encompass the full range of snow accumulation rates observed in East Antarctica, from 25 kg m-2 yr-1 at deep interior sites to >400 kg m-2 yr-1 at near coastal sites. We apply this relationship as a transfer function to an Aurora Basin ice core to produce a 700-year record of accumulation changes. Our nitrate-based estimate compares very well with a parallel reconstruction for Aurora Basin that uses volcanic horizons and ice-penetrating radar. Continued improvements to our database may enable precise independent estimates of millennial-scale accumulation changes using deep ice cores such as EPICA Dome C and Beyond EPICA-Oldest Ice.

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A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

10.5194/cp-2017-101 ◽

2017 ◽

Cited By ~ 8

Author(s):

Mai Winstrup ◽

Paul Vallelonga ◽

Helle A. Kjær ◽

Tyler J. Fudge ◽

James E. Lee ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Early Period ◽

Volcanic Eruptions ◽

Snow Accumulation ◽

Atmospheric Methane ◽

Accumulation Rates ◽

West Antarctica ◽

Ross Ice Shelf ◽

Accumulation History

Abstract. We present a 2700-year annually resolved timescale for the Roosevelt Island Climate Evolution (RICE) ice core, and reconstruct a past snow accumulation history for the coastal sector of the Ross Ice Shelf in West Antarctica. The timescale was constructed by identifying annual layers in multiple ice-core impurity records, employing both manual and automated counting approaches, and constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). The maritime setting of Roosevelt Island results in high sulfate influx from sea salts and marine biogenic emissions, which prohibits a routine detection of volcanic eruptions in the ice-core records. This led to the use of non-traditional chronological techniques for validating the timescale: RICE was synchronized to the WAIS Divide ice core, on the WD2014 timescale, using volcanic attribution based on direct measurements of ice-core acidity, as well as records of globally-synchronous, centennial-scale variability in atmospheric methane concentrations. The RICE accumulation history suggests stable values of 0.25 m water equivalent (w.e.) per year until around 1260 CE. Uncertainties in the correction for ice flow thinning of annual layers with depth do not allow a firm conclusion about long-term trends in accumulation rates during this early period but from 1260 CE to the present, accumulation rate trends have been consistently negative. The decrease in accumulation rates has been increasingly rapid over the last centuries, with the decrease since 1950 CE being more than 7 times greater than the average over the last 300 years. The current accumulation rate of 0.22 ± 0.06 m w.e. yr−1 (average since 1950 CE, ±1σ) is 1.49 standard deviations (86th percentile) below the mean of 50-year average accumulation rates observed over the last 2700 years.

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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.

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Southeast Greenland high accumulation rates derived from firn cores and ground-penetrating radar

Annals of Glaciology ◽

10.3189/2013aog63a358 ◽

2013 ◽

Vol 54 (63) ◽

pp. 322-332 ◽

Cited By ~ 35

Author(s):

Clément Miège ◽

Richard R. Forster ◽

Jason E. Box ◽

Evan W. Burgess ◽

Joseph R. McConnell ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Climate Model ◽

Regional Climate ◽

Elevation Gradient ◽

Greenland Ice Sheet ◽

Snow Accumulation ◽

Internal Layers ◽

Accumulation Rates ◽

High Accumulation ◽

Ground Penetrating

AbstractDespite containing only 14% of the Greenland ice sheet by area, the southeastern sector has the highest accumulation rates, and hence receives ∼30% of the total snow accumulation. We present accumulation rates obtained during our 2010 Arctic Circle Traverse derived from three 50 m firn cores dated using geochemical analysis. We tracked continuous internal reflection horizons between the firn cores using a 400 MHz ground-penetrating radar (GPR). GPR data combined with depth-age scales from the firn cores provide accumulation rates along a 70 km transect. We followed an elevation gradient from ∼2350 to ∼1830m to understand how progressive surface melt may affect the ability to chemically date the firn cores and trace the internal layers with GPR. From the firn cores, we find a 52% (∼0.43 m w.e. a-1) increase in average snow accumulation and greater interannual variability at the lower site than the upper site. The GPR profiling reveals that accumulation rates are influenced by topographic undulations on the surface, with up to 23% variability over 7 km. These measurements confirm the presence of high accumulation rates in the southeast as predicted by the calibrated regional climate model Polar MM5.

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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.

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A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

Climate of the Past ◽

10.5194/cp-15-751-2019 ◽

2019 ◽

Vol 15 (2) ◽

pp. 751-779 ◽

Cited By ~ 9

Author(s):

Mai Winstrup ◽

Paul Vallelonga ◽

Helle A. Kjær ◽

Tyler J. Fudge ◽

James E. Lee ◽

...

Keyword(s):

Sea Ice ◽

Accumulation Rate ◽

Ice Core ◽

Snow Accumulation ◽

Accumulation Rates ◽

West Antarctica ◽

Sea Ice Extent ◽

Amundsen Sea ◽

The Core ◽

Accumulation History

Abstract. We present a 2700-year annually resolved chronology and snow accumulation history for the Roosevelt Island Climate Evolution (RICE) ice core, Ross Ice Shelf, West Antarctica. The core adds information on past accumulation changes in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles in high-resolution impurity records, and it constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanic and methane matching to the WD2014 chronology from the WAIS Divide ice core shows that the two timescales are in excellent agreement. In a companion paper, gas matching to WAIS Divide is used to extend the timescale for the deeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snow accumulation at Roosevelt Island. The accumulation history shows that Roosevelt Island experienced slightly increasing accumulation rates between 700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 m water equivalent (w.e.) per year. Since 1300 CE, trends in the accumulation rate have been consistently negative, with an acceleration in the rate of decline after the mid-17th century. The current accumulation rate at Roosevelt Island is 0.210±0.002 m w.e. yr−1 (average since 1965 CE, ±2σ), and it is rapidly declining with a trend corresponding to 0.8 mm yr−2. The decline observed since the mid-1960s is 8 times faster than the long-term decreasing trend taking place over the previous centuries, with decadal mean accumulation rates consistently being below average. Previous research has shown a strong link between Roosevelt Island accumulation rates and the location and intensity of the Amundsen Sea Low, which has a significant impact on regional sea-ice extent. The decrease in accumulation rates at Roosevelt Island may therefore be explained in terms of a recent strengthening of the ASL and the expansion of sea ice in the eastern Ross Sea. The start of the rapid decrease in RICE accumulation rates observed in 1965 CE may thus mark the onset of significant increases in regional sea-ice extent.

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