Impacts of the photo-driven post-depositional processing on snow nitrate and its isotopes at Summit, Greenland: a model-based study

Abstract. Atmospheric information embedded in ice-core nitrate is disturbed by post-depositional processing. Here we used a layered snow photochemical column model to explicitly investigate the effects of post-depositional processing on snow nitrate and its isotopes (δ15N and Δ17O) at Summit, Greenland, where post-depositional processing was thought to be minimal due to the high snow accumulation rate. We found significant redistribution of nitrate in the upper snowpack through photolysis, and up to 21 % of nitrate was lost and/or redistributed after deposition. The model indicates post-depositional processing can reproduce much of the observed δ15N seasonality, while seasonal variations in δ15N of primary nitrate are needed to reconcile the timing of the lowest seasonal δ15N. In contrast, post-depositional processing can only induce less than 2.1 ‰ seasonal Δ17O change, much smaller than the observation (9 ‰) that is ultimately determined by seasonal differences in nitrate formation pathway. Despite significant redistribution of snow nitrate in the photic zone and the associated effects on δ15N seasonality, the net annual effect of post-depositional processing is relatively small, suggesting preservation of atmospheric signals at the annual scale under the present Summit conditions. But at longer timescales when large changes in snow accumulation rate occur this post-depositional processing could become a major driver of the δ15N variability in ice-core nitrate.

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Impacts of the photo-driven post-depositional processing on snow nitrate and its isotopes at Summit, Greenland: a model-based study

10.5194/tc-2021-92 ◽

2021 ◽

Author(s):

Zhuang Jiang ◽

Becky Alexander ◽

Joel Savarino ◽

Joseph Erbland ◽

Lei Geng

Keyword(s):

Seasonal Variations ◽

Accumulation Rate ◽

Ice Core ◽

Snow Accumulation ◽

Photic Zone ◽

Seasonal Differences ◽

Formation Pathway ◽

Column Model ◽

Annual Scale ◽

Δ15n Variability

Abstract. Atmospheric information embedded in ice-core nitrate is disturbed by post-depositional processing. Here we used a layered snow photochemical column model to explicitly investigate the effects of post-depositional processing on snow nitrate and its isotopes (δ15N and Δ17O) at Summit, Greenland where post-depositional processing was thought to be minimal due to the high snow accumulation rate. We found significant redistribution of nitrate in the upper snowpack through photolysis and up to 21 % of nitrate was lost and/or redistributed after deposition. The model indicates post-depositional processing can reproduce much of the observed δ15N seasonality, while seasonal variations in δ15N of primary nitrate is needed to reconcile the timing of the lowest seasonal δ15N. In contrast, post-depositional processing can only induce less than 2.1 ‰ seasonal Δ17O change, much smaller than the observation (9 ‰) that is ultimately determined by seasonal differences in nitrate formation pathway. Despite significant redistribution of snow nitrate in the photic zone and the associated effects on δ15N seasonality, the net annual effect of post-depositional processing is relatively small, suggesting preservation of atmospheric signals at the annual scale under the present Summit conditions. But at longer timescales when large changes in snow accumulation rate occurs this post-depositional processing could become a major driver of the δ15N variability in ice core nitrate.

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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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Antarctic Anion Glaciochemistry (Abstract only)

Annals of Glaciology ◽

10.1017/s0260305500003311 ◽

1982 ◽

Vol 3 ◽

pp. 354

Author(s):

Michael M. Herron

Keyword(s):

Fossil Fuel ◽

Accumulation Rate ◽

Ice Core ◽

Volcanic Eruptions ◽

Snow Accumulation ◽

Scale Height ◽

Solar Modulation ◽

Fossil Fuel Combustion ◽

Marine Aerosol ◽

Major Anions

Snow and ice-core samples from a number of sites in Antarctica and Greenland have been analyzed for the major anions Cl−, NO3 −, and SO4 2- by ion chromatography. Reproducibility on adjacent core or pit samples is ±10% at the 95% confidence level. Chloride is of marine origin except following some major volcanic eruptions. Chloride concentrations decrease exponentially with increasing site elevation with a scale height of about 1.5 km. For sites of comparable elevation, Antarctic Cl− concentrations are only slightly higher than in Greenland. Sulfate concentrations, corrected for the marine aerosol contribution, show an inverse dependence on snow accumulation rate. For sites of comparable accumulation rate, Greenland concentrations exceed those in Antarctica by a factor of 2 to 3. Nitrate concentrations also decrease with increasing accumulation rate and for comparable sites Greenland NO3 − concentrations are a factor of 2 higher than in Antarctica. There is no evidence of solar modulation or supernova perturbation of Greenland NO3 − concentrations. The Byrd deep core is shown to have distinct seasonal variations in Cl− and SO4 2- that may be used for dating. In addition, the Byrd core contains volcanic signals similar to those found in Greenland. Recent Greenland snow contains about 4 times as much SO4 2- and 2 to 3 times as much NO3 − as is found in older ice due to modern fossil fuel combustion.

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Investigation of the 18O Content of a 100 m Ice Core From the Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500004146 ◽

1988 ◽

Vol 10 ◽

pp. 43-47 ◽

Cited By ~ 5

Author(s):

W. Graf ◽

O. Reinwarth ◽

H. Moser ◽

W. Stichler

Keyword(s):

Flow Model ◽

Accumulation Rate ◽

Ice Core ◽

Snow Accumulation ◽

Two Dimensional ◽

Ice Shelf ◽

Short Term ◽

The Core ◽

Two Dimensional Flow ◽

Field Season

A 100 m ice core from the Ronne Ice Shelf, drilled during the 1983-84 field season, was dated by isotopic stratigraphy, using the well-known seasonal variation in the 18O content in firn and ice; the layers at a depth of 89 m are probably 400 years old. Layer thicknesses deduced from the 18O profile indicate short-term variations of the snow-accumulation rate over the last 400 years. The area of deposition of the material recovered with the core is estimated by a two-dimensional flow model and by the 18O content of the core, which decreases from –27.5‰ in the upper part of the core to –32.0‰ at 89 m depth.

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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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Antarctic Anion Glaciochemistry (Abstract only)

Annals of Glaciology ◽

10.3189/s0260305500003311 ◽

1982 ◽

Vol 3 ◽

pp. 354-354

Author(s):

Michael M. Herron

Keyword(s):

Fossil Fuel ◽

Accumulation Rate ◽

Ice Core ◽

Volcanic Eruptions ◽

Snow Accumulation ◽

Scale Height ◽

Solar Modulation ◽

Fossil Fuel Combustion ◽

Marine Aerosol ◽

Major Anions

Snow and ice-core samples from a number of sites in Antarctica and Greenland have been analyzed for the major anions Cl−, NO3−, and SO42- by ion chromatography. Reproducibility on adjacent core or pit samples is ±10% at the 95% confidence level. Chloride is of marine origin except following some major volcanic eruptions. Chloride concentrations decrease exponentially with increasing site elevation with a scale height of about 1.5 km. For sites of comparable elevation, Antarctic Cl− concentrations are only slightly higher than in Greenland. Sulfate concentrations, corrected for the marine aerosol contribution, show an inverse dependence on snow accumulation rate. For sites of comparable accumulation rate, Greenland concentrations exceed those in Antarctica by a factor of 2 to 3. Nitrate concentrations also decrease with increasing accumulation rate and for comparable sites Greenland NO3− concentrations are a factor of 2 higher than in Antarctica. There is no evidence of solar modulation or supernova perturbation of Greenland NO3− concentrations. The Byrd deep core is shown to have distinct seasonal variations in Cl− and SO42- that may be used for dating. In addition, the Byrd core contains volcanic signals similar to those found in Greenland. Recent Greenland snow contains about 4 times as much SO42- and 2 to 3 times as much NO3− as is found in older ice due to modern fossil fuel combustion.

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Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past-temperature reconstructions

The Cryosphere ◽

10.5194/tc-9-1481-2015 ◽

2015 ◽

Vol 9 (4) ◽

pp. 1481-1504 ◽

Cited By ~ 29

Author(s):

V. Masson-Delmotte ◽

H. C. Steen-Larsen ◽

P. Ortega ◽

D. Swingedouw ◽

T. Popp ◽

...

Keyword(s):

19Th Century ◽

North Atlantic ◽

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

Last Interglacial ◽

Bottom Part ◽

Recent Climate ◽

Temperature Reconstructions

Abstract. Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (North Greenland Eemian Ice Drilling), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterise the isotope–temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic sea surface temperature and is enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multidecadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815–1825 and 1836–1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multidecadal accumulation–temperature and δ18O–temperature relationships for the strong warming period in 1979–2007. The accumulation sensitivity to temperature is estimated at 11 ± 2 % °C−1 and the δ18O–temperature slope at 1.1 ± 0.2 ‰ °C−1, about twice as large as previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

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Simulating ice core <sup>10</sup>Be on the glacial–interglacial timescale

Climate of the Past ◽

10.5194/cp-11-115-2015 ◽

2015 ◽

Vol 11 (2) ◽

pp. 115-133 ◽

Cited By ~ 7

Author(s):

C. Elsässer ◽

D. Wagenbach ◽

I. Levin ◽

A. Stanzick ◽

M. Christl ◽

...

Keyword(s):

Transport Model ◽

Atmospheric Transport ◽

Accumulation Rate ◽

Ice Core ◽

Global Scale ◽

Snow Accumulation ◽

Transfer Model ◽

Ice Concentration ◽

Model Measurement ◽

Ice Core Records

Abstract. 10Be ice core measurements are an important tool for paleoclimate research, e.g., allowing for the reconstruction of past solar activity or changes in the geomagnetic dipole field. However, especially on multi-millennial timescales, the share of production and climate-induced variations of respective 10Be ice core records is still up for debate. Here we present the first quantitative climatological model of the 10Be ice concentration up to the glacial–interglacial timescale. The model approach is composed of (i) a coarse resolution global atmospheric transport model and (ii) a local 10Be air–firn transfer model. Extensive global-scale observational data of short-lived radionuclides as well as new polar 10Be snow-pit measurements are used for model calibration and validation. Being specifically configured for 10Be in polar ice, this tool thus allows for a straightforward investigation of production- and non-production-related modulation of this nuclide. We find that the polar 10Be ice concentration does not immediately record the globally mixed cosmogenic production signal. Using geomagnetic modulation and revised Greenland snow accumulation rate changes as model input, we simulate the observed Greenland Summit (GRIP and GISP2) 10Be ice core records over the last 75 kyr (on the GICC05modelext timescale). We show that our basic model is capable of reproducing the largest portion of the observed 10Be changes. However, model–measurement differences exhibit multi-millennial trends (differences up to 87% in case of normalized to the Holocene records) which call for closer investigation. Focusing on the (12–37) b2k (before the year AD 2000) period, mean model–measurement differences of 30% cannot be attributed to production changes. However, unconsidered climate-induced changes could likely explain the model–measurement mismatch. In fact, the 10Be ice concentration is very sensitive to snow accumulation changes. Here the reconstructed Greenland Summit (GRIP) snow accumulation rate record would require revision of +28% to solely account for the (12–37) b2k model–measurement differences.

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Sulphuric and Nitric Acid Concentrations and Spikes Along A 200 m Deep Ice Core at D 57 (Terre Adélie, Antarctica)

Annals of Glaciology ◽

10.1017/s0260305500005930 ◽

1985 ◽

Vol 7 ◽

pp. 70-75 ◽

Cited By ~ 21

Author(s):

Françoise Zanolini ◽

Robert J. Delmas ◽

Michel Legrand

Keyword(s):

Nitric Acid ◽

Accumulation Rate ◽

Ice Core ◽

Volcanic Eruptions ◽

Snow Accumulation ◽

The Other ◽

Background Concentration ◽

Volcanic Events ◽

Mineral Acids ◽

Terre Adélie

D 57 station in Terre Adélie lies between the coast and the central Antarctic plateau. A 200 m ice core was recovered in summer 1980–81 at this location and analyzed by an electroconductometric method to detect exceptional acid levels linked to fallout from major volcanic eruptions. Several signals were indeed found. The corresponding ice-core sections were then analyzed for mineral acids (H2SO4 and HNO3). We detected several large volcanic events, in particular two eruptions identified as Tarabora (1815) and Galunggung (1822). The background concentration of sulphate was found to be relatively low (about 0.5 μeq 1−1). On the other hand nitrate values were higher than at coastal or central Antarctic locations (except for the Sauth Pole). Two spikes were found in the nitrate profile at depths of 140 and 148 m. It is thought that they could be either linked to the 1604 and 1572 supernovae Kepler and Tycho or correspond to epochs of particularly high solar activities. With the aid of these sulphate and nitrate exceptional events, a dating of the D 57 ice core can now be proposed which corresponds to a mean snow accumulation rate of 22 cm of ice equivalent per year over the last four centuries.

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Sensitivity of chemical species to climatic changes in the last 45 kyr as revealed by high-resolution Dome C (East Antarctica) ice-core analysis

Annals of Glaciology ◽

10.3189/172756404781814096 ◽

2004 ◽

Vol 39 ◽

pp. 457-466 ◽

Cited By ~ 13

Author(s):

Roberto Udisti ◽

Silvia Becagli ◽

Silvia Benassai ◽

Martine De Angelis ◽

Margareta E. Hansson ◽

...

Keyword(s):

High Resolution ◽

Environmental Changes ◽

Accumulation Rate ◽

Ice Core ◽

Chemical Species ◽

Climatic Changes ◽

Snow Accumulation ◽

Last Deglaciation ◽

Temperature Trends ◽

Chemical Profiles

AbstractTo assess the cause/effect relationship between climatic and environmental changes, we report high-resolution chemical profiles of the Dome C ice core (788m, 45 kyr), drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA). Snow-concentration and depositional-flux changes during the last deglaciation were compared with climatic changes, derived by δD profile. Concentration and temperature profiles showed an anticorrelation, driven by changes in source intensity and transport efficiency of the atmospheric aerosol and by snow accumulation-rate variations. The flux calculation allowed correction for accumulation rate. While sulphate and ammonium fluxes are quite constant, Na+, Mg2+ and Ca2+ underwent the greatest changes, showing fluxes respectively about two, three and six times lower in the Holocene than in the Last Glacial Maximum. Chloride, nitrate and methanesulphonic acid (MSA) also exhibited large changes, but their persistence depends on depositional and post-depositional effects. The comparison between concentrations and δD profiles revealed leads and lags between chemical and temperature trends: Ca2+ and nitrate preceded by about 300 years the δD increase at the deglaciation onset, while MSA showed a 400 year delay. Generally, all components reached low Holocene values in the first deglaciation step (18.0–14.0 kyr BP), but Na+, Mg2+ and nitrate show changes during the Antarctic Cold Reversal (14.0– 12.5 kyr BP).

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