scholarly journals Methanesulfonic acid (MSA) migration in polar ice: Data synthesis and theory

2017 ◽  
Author(s):  
Matthew Osman ◽  
Sarah B. Das ◽  
Olivier Marchal ◽  
Matthew J. Evans
Keyword(s):  
Transport Model ◽  
Accumulation Rate ◽  
Ice Core ◽  
Methanesulfonic Acid ◽  
Snow Accumulation ◽  
Polar Ice ◽  
Impurity Transport ◽  
Phase Alignment ◽  
Wide Range ◽  
Soluble Impurity

Abstract. Methanesulfonic acid (MSA; CH3SO3H) in polar ice is a unique proxy of marine primary productivity, synoptic atmospheric transport, and regional sea ice behavior. However, MSA can be mobile within the firn and ice matrix, a post-depositional process that is well known but poorly understood and documented, leading to uncertainties in the integrity of the MSA paleoclimatic signal. Here, we use a compilation of 22 ice core MSA records from Greenland and Antarctica and a model of soluble impurity transport in order to comprehensively investigate the vertical migration of MSA from summer layers, where MSA is originally deposited, to adjacent winter layers in polar ice. The shallowest depths of MSA migration reported in our compilation vary over a wide range (~ 2 m to 400 m), and our analysis suggests that these depths are positively correlated with snow accumulation rate and negatively correlated with ice concentration of Na+ (typically the most abundant cationic sea salt). Although the considered soluble impurity transport model provides a useful mechanistic framework for studying MSA migration, it remains limited by inadequate constraints on key physicochemical parameters, most notably, the diffusion coefficient of MSA in cold ice (DMS). We derive a simplified version of the model, which includes DMS as the sole parameter, in order to illuminate aspects of the migration process. Using this model, we show that the progressive phase alignment of MSA and Na+ concentration peaks observed along a high-resolution West Antarctic core is most consistent with 10–12 m2 s-1 

scholarly journals Methanesulfonic acid (MSA) migration in polar ice: data synthesis and theory

2017 ◽  
Vol 11 (6) ◽  
pp. 2439-2462 ◽  
Author(s):  
Matthew Osman ◽  
Sarah B. Das ◽  
Olivier Marchal ◽  
Matthew J. Evans
Keyword(s):  
Transport Model ◽  
Ice Core ◽  
Methanesulfonic Acid ◽  
Snow Accumulation ◽  
Polar Ice ◽  
Data Synthesis ◽  
Impurity Transport ◽  
Phase Alignment ◽  
Wide Range ◽  
Soluble Impurity

Abstract. Methanesulfonic acid (MSA; CH3SO3H) in polar ice is a unique proxy of marine primary productivity, synoptic atmospheric transport, and regional sea-ice behavior. However, MSA can be mobile within the firn and ice matrix, a post-depositional process that is well known but poorly understood and documented, leading to uncertainties in the integrity of the MSA paleoclimatic signal. Here, we use a compilation of 22 ice core MSA records from Greenland and Antarctica and a model of soluble impurity transport in order to comprehensively investigate the vertical migration of MSA from summer layers, where MSA is originally deposited, to adjacent winter layers in polar ice. We find that the shallowest depth of MSA migration in our compilation varies over a wide range (∼ 2 to 400 m) and is positively correlated with snow accumulation rate and negatively correlated with ice concentration of Na+ (typically the most abundant marine cation). Although the considered soluble impurity transport model provides a useful mechanistic framework for studying MSA migration, it remains limited by inadequate constraints on key physico-chemical parameters – most notably, the diffusion coefficient of MSA in cold ice (DMS). We derive a simplified version of the model, which includes DMS as the sole parameter, in order to illuminate aspects of the migration process. Using this model, we show that the progressive phase alignment of MSA and Na+ concentration peaks observed along a high-resolution West Antarctic core is most consistent with 10−12 m2 s−1 < DMS < 10−11 m2 s−1, which is 1 order of magnitude greater than the DMS values previously estimated from laboratory studies. More generally, our data synthesis and model results suggest that (i) MSA migration may be fairly ubiquitous, particularly at coastal and (or) high-accumulation regions across Greenland and Antarctica; and (ii) can significantly change annual and multiyear MSA concentration averages. Thus, in most cases, caution should be exercised when interpreting polar ice core MSA records, although records that have undergone severe migration could still be useful for inferring decadal and lower-frequency climate variability.

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

2015 ◽  
Vol 11 (2) ◽  
pp. 115-133 ◽  
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.

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

2014 ◽  
Vol 10 (1) ◽  
pp. 761-808 ◽  
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 ◽  
10Be Concentration ◽  
Ice Concentration ◽  
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 variation in the natural 14C production rate. However, especially on multi-millennial timescales, the share of production and climate induced variations of respective 10Be ice core records is still up to 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 polar 10Be, this tool thus allows for a straight-forward investigation of production and non-production related modulation of this nuclide. We find that the polar 10Be ice concentration does not record a globally mixed cosmogenic production signal. In fact, the geomagnetic modulation of Greenland 10Be is up to 50% lower than in case of the global atmospheric 10Be inventory. 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 to reproduce the largest portion of the observed 10Be changes. However, model-measurements differences exhibit multi-millennial oscillations with amplitudes up to 87% of the mean observed Holocene 10Be concentration. Focusing on the (12–37) kyr b2k (before the year 2000 AD) period, mean model-measurements differences of 30% cannot be imputed to production changes. However, unconsidered climate-induced changes could likely explain the model shortcomings. 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) kyr b2k measurements-model differences.

scholarly journals Deposition, recycling and archival of nitrate stable isotopes between the air-snow interface: comparison between Dronning Maud Land and Dome C, Antarctica

2019 ◽  
Author(s):  
V. Holly L. Winton ◽  
Alison Ming ◽  
Nicolas Caillon ◽  
Lisa Hauge ◽  
Anna E. Jones ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Skin Layer ◽  
Snow Accumulation ◽  
Snow Pack ◽  
Polar Ice ◽  
Depth Profiles ◽  
Dronning Maud Land

Abstract. The nitrate (NO3−) isotopic composition δ15N-NO3− of polar ice cores has the potential to provide constraints on past ultraviolet (UV) radiation and thereby total column ozone (TCO), in addition to the oxidising capacity of the ancient atmosphere. However, understanding the transfer of reactive nitrogen at the air-snow interface in Polar Regions is paramount for the interpretation of ice core records of δ15N-NO3− and NO3− mass concentrations. As NO3− undergoes a number of post-depositional processes before it is archived in ice cores, site-specific observations of δ15N-NO3− and air-snow transfer modelling are necessary in order to understand and quantify the complex photochemical processes at play. As part of the Isotopic Constraints on Past Ozone Layer Thickness in Polar Ice (ISOL-ICE) project, we report new measurements of NO3− concentration and δ15N-NO3− in the atmosphere, skin layer (operationally defined as the top 5 mm of the snow pack), and snow pit depth profiles at Kohnen Station, Dronning Maud Land (DML), Antarctica. We compare the results to previous studies and new data, presented here, from Dome C, East Antarctic Plateau. Additionally, we apply the conceptual one-dimensional model of TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) to assess the impact of photochemical processes that drive the archival of δ15N-NO3− and NO3− in the snow pack. We find clear evidence of NO3− photolysis at DML, and confirmation of our hypothesis that UV-photolysis is driving NO3− recycling at DML. Firstly, strong denitrification of the snow pack is observed through the δ15N-NO3− signature which evolves from the enriched snow pack (−3 to 100 ‰), to the skin layer (−20 to 3 ‰), to the depleted atmosphere (−50 to −20 ‰) corresponding to mass loss of NO3− from the snow pack. Secondly, constrained by field measurements of snow accumulation rate, light attenuation (e-folding depth) and atmospheric NO3− mass concentrations, the TRANSITS model is able to reproduce our δ15N-NO3− observations in depth profiles. We find that NO3− is recycled three times before it is archived (i.e., below the photic zone) in the snow pack below 15 cm and within 0.75 years. Archived δ15N-NO3− and NO3− concentration values are 50 ‰ and 60 ng g−1 at DML. NO3− photolysis is weaker at DML than at Dome C, due primarily to the higher DML snow accumulation rate; this results in a more depleted δ15N-NO3− signature at DML than at Dome C. Even at a relatively low snow accumulation rate of 6 cm yr−1 (water equivalent; w.e.), the accumulation rate at DML is great enough to preserve the seasonal cycle of NO3− concentration and δ15N-NO3−, in contrast to Dome C where the profiles are smoothed due to stronger photochemistry. TRANSITS sensitivity analysis of δ15N-NO3− at DML highlights that the dominant factors controlling the archived δ15N-NO3− signature are the snow accumulation rate and e-folding depth, with a smaller role from changes in the snowfall timing and TOC. Here we set the framework for the interpretation of a 1000-year ice core record of δ15N-NO3− from DML. Ice core δ15N-NO3− records at DML will be less sensitive to changes in UV than at Dome C, however the higher snow accumulation rate and more accurate dating at DML allows for higher resolution δ15N-NO3− records.

scholarly journals Chronological characteristics for snow accumulation on Styx Glacier in northern Victoria Land, Antarctica

2020 ◽  
Vol 66 (260) ◽  
pp. 916-926
Author(s):  
Yalalt Nyamgerel ◽  
Yeongcheol Han ◽  
Songyi Kim ◽  
Sang-Bum Hong ◽  
Jeonghoon Lee ◽  
...  
Keyword(s):  
Ross Sea ◽  
Accumulation Rate ◽  
Ice Core ◽  
Methanesulfonic Acid ◽  
Open Water ◽  
Water Area ◽  
Snow Accumulation ◽  
Atmospheric Conditions ◽  
Sea Ice Extent ◽  
Firn Core

AbstractUnder the potential to reconstruct the past climatic and atmospheric conditions from a deep ice core in the coastal Antarctic site (Styx Glacier), an 8.84 m long firn core (73°50.975′ S, 163°41.640′ E; 1623 m a.s.l.) was initially studied to propose a reliable age scale for the local estimation of snow accumulation rate. The seasonal variations of δ18O, methanesulfonic acid (MSA) and non-sea-salt sulfate (nssSO42–) were used for the firn core dating and revealed 25 annual peaks (from 1990 to 2014) with volcanic sulfate signal. The observed declining trend in annual accumulation rate with a mean value of 146 ± 60 kg m–2 a–1 is likely to be linked to the changes of sea-ice extent in the Ross Sea region. Moreover, the temporal variation of the annual mean δ18O, an annual flux of MSA and nssSO42– also likely to be under the influence of ice-covered and open water area. This study suggests a potential to recover past changes in an oceanic environment and will be useful for the interpretation of the long ice core drilled at the same site.

scholarly journals Dating of an East Antarctic ice core (GV7) by high resolution chemical stratigraphies

2021 ◽  
Author(s):  
Raffaello Nardin ◽  
Mirko Severi ◽  
Alessandra Amore ◽  
Silvia Becagli ◽  
Francois Burgay ◽  
...  
Keyword(s):  
Environmental Changes ◽  
18Th Century ◽  
Accumulation Rate ◽  
Ice Core ◽  
Methanesulfonic Acid ◽  
Oxygen Isotopic Composition ◽  
Snow Accumulation ◽  
Sea Salt ◽  
The Core ◽  
History Of

Abstract. Ice core dating is the first step for a correct interpretation of climatic and environmental changes. In this work, we release a stratigraphic dating of the uppermost 197 m of the 250 m deep GV7(B) ice core (drilling site, 70°41’S, 158°52’E, 1950 m a.s.l.) with a sub-annual resolution. Chemical stratigraphies of NO3−, MSA (methanesulfonic acid), non-sea salt SO42−, sea-salt ions and the oxygen isotopic composition (δ18O) were used in the annual layer counting upon the identification of a seasonal profile in their records. Different procedures were tested and thanks to the volcanic history of the core, obtained in previous works, an accurate age-depth correlation was obtained for the period 1179–2009 CE. Once the dating of the core was finalized, the annual mean accumulation rate was evaluated throughout the analyzed 197 m of the core, obtaining an annually resolved history of the snow accumulation on site in the last millennium. A small, yet consistent, rise in accumulation rate was found for the last 830 years since the middle of the 18th century.

scholarly journals A review of the brittle ice zone in polar ice cores

2014 ◽  
Vol 55 (68) ◽  
pp. 72-82 ◽  
Author(s):  
Peter D. Neff
Keyword(s):  
Atmospheric Pressure ◽  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Air Bubbles ◽  
Polar Ice ◽  
Overburden Pressure ◽  
Trapped Air ◽  
Borehole Temperatures

AbstractMaintaining ice-core quality through the brittle ice zone (BIZ) remains challenging for polar ice-core studies. At depth, increasing ice overburden pressurizes trapped air bubbles, causing fracture of cores upon exposure to atmospheric pressure. Fractured ice cores degrade analyses, reducing resolution and causing contamination. BIZ encounters at 18 sites across the Greenland, West and East Antarctic ice sheets are documented. The BIZ begins at a mean depth of 545 ± 162 m (1 standard deviation), extending to depths where ductile clathrate ice is reached: an average of 1132 ± 178 m depth. Ice ages in this zone vary with snow accumulation rate and ice thickness, beginning as young as 2 ka BP at Dye-3, Greenland, affecting ice >160 ka BP in age at Taylor Dome, Antarctica, and compromising up to 90% of retrieved samples at intermediate-depth sites. Effects of pressure and temperature on the BIZ are explored using modeled firn-column overburden pressure and borehole temperatures, revealing complex associations between firn densification and BIZ depth, and qualitatively supporting expected thinning of the BIZ at low ice temperatures due to shallower clathrate stability. Mitigating techniques for drilling, transport, sampling and analysis of brittle ice cores are also discussed.

scholarly journals Dating of the GV7 East Antarctic ice core by high-resolution chemical records and focus on the accumulation rate variability in the last millennium

2021 ◽  
Vol 17 (5) ◽  
pp. 2073-2089
Author(s):  
Raffaello Nardin ◽  
Mirko Severi ◽  
Alessandra Amore ◽  
Silvia Becagli ◽  
Francois Burgay ◽  
...  
Keyword(s):  
Environmental Changes ◽  
18Th Century ◽  
Accumulation Rate ◽  
Seasonal Pattern ◽  
Ice Core ◽  
Methanesulfonic Acid ◽  
Snow Accumulation ◽  
Sea Salt ◽  
Last Millennium ◽  
Annual Layer

Abstract. Ice core dating is the first step for a correct interpretation of climatic and environmental changes. In this work, we release the dating of the uppermost 197 m of the 250 m deep GV7(B) ice core (drill site, 70∘41′ S, 158∘52′ E; 1950 m a.s.l. in Oates Land, East Antarctica) with a sub-annual resolution. Chemical records of NO3-, MSA (methanesulfonic acid), non-sea-salt SO42- (nssSO42-), sea-salt ions and water stable isotopes (δ18O) were studied as candidates for dating due to their seasonal pattern. Different procedures were tested but the nssSO42- record proved to be the most reliable on the short- and long-term scales, so it was chosen for annual layer counting along the whole ice core. The dating was constrained by using volcanic signatures from historically known events as tie points, thus providing an accurate age–depth relationship for the period 1179–2009 CE. The achievement of the complete age scale allowed us to calculate the annual mean accumulation rate throughout the analyzed 197 m of the core, yielding an annually resolved history of the snow accumulation on site in the last millennium. A small yet consistent rise in accumulation rate (Tr = 1.6, p<0.001) was found for the last 830 years starting around mid-18th century.

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

2017 ◽  
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.

Environmental records from polar ice cores

1990 ◽  
Vol 330 (1615) ◽  
pp. 459-462 ◽  
Keyword(s):  
Solar Activity ◽  
Ice Core ◽  
Ice Cores ◽  
Polar Ice ◽  
Cosmogenic Isotope ◽  
Wide Range ◽  
Recent Part ◽  
Ice Core Records

Polar ice cores provide a wide range of information on past atmospheric climate (temperature, precipitation) and environment (gas and aerosol concentrations). The dating can be very accurate for the more recent part of the records but accuracy decreases with depth and time. Measurements of cosmogenic isotope concentrations (such as 10 Be) provide information on palaeo-precipitation rates and particular events can be used to correlate ice core records. Besides these climatic applications, 10 Be concentration records in ice cores also contain information on solar activity changes.

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