scholarly journals Photolysis imprint in the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling

2009 ◽  
Vol 9 (22) ◽  
pp. 8681-8696 ◽  
Author(s):  
M. M. Frey ◽  
J. Savarino ◽  
S. Morin ◽  
J. Erbland ◽  
J. M. F. Martins
Keyword(s):  
Ice Cores ◽  
High Sensitivity ◽  
Field Measurements ◽  
Skin Layer ◽  
Reactive Nitrogen ◽  
The Earth ◽  
15N Enrichment ◽  
Oxygen Stable Isotopes ◽  
Uv Lamp ◽  
Isotopic Signal

Abstract. The nitrogen (δ15N) and triple oxygen (δ17O and δ18O) isotopic composition of nitrate (NO3−) was measured year-round in the atmosphere and snow pits at Dome C, Antarctica (DC, 75.1° S, 123.3° E), and in surface snow on a transect between DC and the coast. Comparison to the isotopic signal in atmospheric NO3− shows that snow NO3− is significantly enriched in δ15N by >200‰ and depleted in δ18O by <40‰. Post-depositional fractionation in Δ17O(NO3−) is small, potentially allowing reconstruction of past shifts in tropospheric oxidation pathways from ice cores. Assuming a Rayleigh-type process we find fractionation constants ε of −60±15‰, 8±2‰ and 1±1‰, for δ15N, δ18O and Δ17O, respectively. A photolysis model yields an upper limit for the photolytic fractionation constant 15ε of δ15N, consistent with lab and field measurements, and demonstrates a high sensitivity of 15ε to the incident actinic flux spectrum. The photolytic 15ε is process-specific and therefore applies to any snow covered location. Previously published 15ε values are not representative for conditions at the Earth surface, but apply only to the UV lamp used in the reported experiment (Blunier et al., 2005; Jacobi et al., 2006). Depletion of oxygen stable isotopes is attributed to photolysis followed by isotopic exchange with water and hydroxyl radicals. Conversely, 15N enrichment of the NO3− fraction in the snow implies 15N depletion of emissions. Indeed, δ15N in atmospheric NO3− shows a strong decrease from background levels (4±7‰) to −35‰ in spring followed by recovery during summer, consistent with significant snowpack emissions of reactive nitrogen. Field and lab evidence therefore suggest that photolysis is an important process driving fractionation and associated NO3− loss from snow. The Δ17O signature confirms previous coastal measurements that the peak of atmospheric NO3− in spring is of stratospheric origin. After sunrise photolysis drives then redistribution of NO3− from the snowpack photic zone to the atmosphere and a snow surface skin layer, thereby concentrating NO3− at the surface. Little NO3− appears to be exported off the EAIS plateau, still snow emissions from as far as 600 km inland can contribute to the coastal NO3− budget.

scholarly journals Photolytic control of the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling

2009 ◽  
Vol 9 (3) ◽  
pp. 12559-12596 ◽  
Author(s):  
M. M. Frey ◽  
J. Savarino ◽  
S. Morin ◽  
J. Erbland ◽  
J. M. F. Martins
Keyword(s):  
Isotopic Exchange ◽  
Isotopic Fractionation ◽  
Ice Cores ◽  
Skin Layer ◽  
Reactive Nitrogen ◽  
Lab Experiments ◽  
15N Enrichment ◽  
Oxygen Stable Isotopes ◽  
Significant Enrichment ◽  
Isotopic Signal

Abstract. The nitrogen (δ15N) and triple oxygen (δ17/18O) isotopic composition of nitrate (NO3−) was measured year-round in the atmosphere and snow pits at Dome C (DC, 75.1° S, 123.3° E), and in surface snow on a transect between DC and the coast. Snow pit profiles of δ15N (δ18O) in NO3− show significant enrichment (depletion) of >200 (<40) ‰ compared to the isotopic signal in atmospheric NO3−, whereas post-depositional fractionation in Δ17O(NO3−) is small, allowing reconstruction of past shifts in tropospheric oxidation pathways from ice cores. Assuming a Rayleigh-type process we find in the DC04 (DC07) pit fractionation factors ε of −50±10 (−71±12) ‰, 6±3 (9±2) ‰ and 1±0.2 (2±0.6) ‰, for δ15N, δ18O and Δ17O, respectively. A photolysis model reproduces ε for δ15N within the range of uncertainty at DC and for lab experiments reported by Blunier et al. (2005), suggesting that the current literature value for photolytic isotopic fractionation in snow is significantly underestimated. Depletion of oxygen stable isotopes is attributed to photolysis followed by isotopic exchange with water and hydroxyl radicals. Conversely, 15N enrichment of the NO3− fraction in the snow implies 15N depletion of emissions. Indeed, δ15N in atmospheric NO3− shows a strong decrease from background levels (4.4±6.8‰) to −35.1‰ in spring followed by recovery during summer, consistent with significant snow pack emissions of reactive nitrogen. Field and lab evidence therefore suggest that photolysis dominates fractionation and associated NO3− loss from snow in the low-accumulation regions of the East Antarctic Ice Sheet (EAIS). The Δ17O signature confirms previous coastal measurements that the peak of atmospheric NO3− in spring is of stratospheric origin. After sunrise photolysis drives then redistribution of NO3− from the snowpack photic zone to the atmosphere and a snow surface skin layer, thereby concentrating NO3− at the surface. Little NO3− is exported off the EAIS plateau, still snow emissions from as far as 600 km inland can contribute to the coastal NO3− budget.

scholarly journals Continuous in-field measurements of gas concentration from ice cores

PAGES news ◽  
2013 ◽  
Vol 21 (1) ◽  
pp. 34-35
Author(s):  
Thomas Blunier ◽  
J Chappellaz ◽  
E Brook
Keyword(s):  
Ice Cores ◽  
Field Measurements ◽  
Gas Concentration

scholarly journals Effects of temperature variations in high-sensitivity Sagnac gyroscope

2021 ◽  
Vol 136 (5) ◽  
Author(s):  
Andrea Basti ◽  
Nicolò Beverini ◽  
Filippo Bosi ◽  
Giorgio Carelli ◽  
Donatella Ciampini ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Mechanical Design ◽  
Low Frequency ◽  
Environmental Parameters ◽  
High Sensitivity ◽  
Rotation Axes ◽  
The Earth ◽  
Sagnac Gyroscope ◽  
Laser Gyroscopes

AbstractGINGERINO is one of the most sensitive Sagnac laser-gyroscopes based on an heterolithic mechanical structure. It is a prototype for GINGER, the laser gyroscopes array proposed to reconstruct the Earth rotation vector and in this way to measure General Relativity effects. Many factors affect the final sensitivity of laser gyroscopes, in particular, when they are used in long-term measurements, slow varying environmental parameters come into play. To understand the role of different terms allows to design more effective mechanical as well as optical layouts, while a proper model of the dynamics affecting long-term (low frequency) signals would increase the effectiveness of the data analysis for improving the overall sensitivity. In this contribution, we focus our concerns on the effects of room temperature and pressure aiming at further improving mechanical design and long-term stability of the apparatus. Our data are compatible with a local orientation changes of the Gran Sasso site below $$\mu $$ μ rad as predicted by geodetic models. This value is consistent with the requirements for GINGER and the installation of an high-sensitivity Sagnac gyroscope oriented at the maximum signal, i.e. along the Earth rotation axes.

scholarly journals Application of the radionuclide 210Pb in glaciology – an overview

2020 ◽  
Vol 66 (257) ◽  
pp. 447-456 ◽  
Author(s):  
Heinz W. Gäggeler ◽  
Leonhard Tobler ◽  
Margit Schwikowski ◽  
Theo M. Jenk
Keyword(s):  
Half Life ◽  
Arid Regions ◽  
Noble Gas ◽  
Radioactive Decay ◽  
Ice Cores ◽  
Snow Accumulation ◽  
The Earth ◽  
Special Cases ◽  
Glacier Flow

Abstract210Pb is an environmental radionuclide with a half-life of 22.3 years, formed in the atmosphere via radioactive decay of radon (222Rn). 222Rn itself is a noble gas with a half-life of 3.8 days and is formed via radioactive decay of uranium (238U) contained in the Earth crust from where it constantly emanates into the atmosphere. 210Pb atoms attach to aerosol particles, which are then deposited on glaciers via scavenging with fresh snow. Due to its half-life, ice cores can be dated with this radionuclide over roughly one century, depending on the initial 210Pb activity concentration. Optimum 210Pb dating is achieved for cold glaciers with no – or little – influence by percolating meltwater. This paper presents an overview which not only includes dating of cold glaciers but also some special cases of 210Pb applications in glaciology addressing temperate glaciers, glaciers with negative mass balance, sublimation processes on glaciers in arid regions, determination of annual net snow accumulation as well as glacier flow rates.

The effect of plasmaspheric material on magnetopause reconnection

2020 ◽  
Author(s):  
Stephen Fuselier ◽  
Stein Haaland ◽  
Paul Tenfjord ◽  
David Malaspina ◽  
James Burch ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Magnetic Reconnection ◽  
Plasma Wave ◽  
Outer Part ◽  
Field Measurements ◽  
Ion Composition ◽  
The Earth ◽  
Magnetospheric Multiscale ◽  
Magnetic Field Measurements

&lt;p&gt;The Earth&amp;#8217;s plasmasphere contains cold (~eV energy) dense (&gt;100 cm&lt;sup&gt;-3&lt;/sup&gt;) plasma of ionospheric origin. The primary ion constituents of the plasmasphere are H&lt;sup&gt;+&amp;#160;&lt;/sup&gt;and He&lt;sup&gt;+&lt;/sup&gt;, and a lower concentration of O&lt;sup&gt;+&lt;/sup&gt;. The outer part of the plasmasphere, especially on the duskside of the Earth, drains away into the dayside outer magnetosphere when geomagnetic activity increases. Because of its high density and low temperature, this plasma has the potential to modify magnetic reconnection at the magnetopause. To investigate the effect of plasmaspheric material at the magnetopause, Magnetospheric Multiscale (MMS) data are surveyed to identify magnetopause crossings with the highest He&lt;sup&gt;+&lt;/sup&gt;densities. Plasma wave, ion, and ion composition data are used to determine densities and mass densities of this plasmaspheric material and the magnetosheath plasma adjacent to the magnetopause. These measurements are combined with magnetic field measurements to determine how the highest density plasmaspheric material in the MMS era may affect reconnection at the magnetopause.&lt;/p&gt;

Simulating the seasonal cycle of 13C

2020 ◽  
Author(s):  
Sebastian Lienert ◽  
Christoph Köstler ◽  
Sönke Zaehle ◽  
Fortunat Joos
Keyword(s):  
Seasonal Cycle ◽  
Atmospheric Transport ◽  
High Sensitivity ◽  
System Model ◽  
Atmospheric Measurements ◽  
Vegetation Model ◽  
Dynamic Global Vegetation Model ◽  
The Earth ◽  
Long Lifetime ◽  
Global Vegetation

&lt;p&gt;We investigate the seasonal cycle of &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; using the Earth system model of intermediate complexity Bern3D-LPX. Using a model of atmospheric transport (TM3), the spatial fields of simulated &lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; exchange are translated to local &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; anomalies, which are then compared to atmospheric measurements. We discuss the ability of the model to accurately simulate the atmospheric seasonal &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2 &lt;/sub&gt;cycle&lt;sub&gt;, &lt;/sub&gt;which could prove to be a valuable novel observational constraint. The coupled simulation allows us to distinguish the relative importance of the biosphere and ocean in determining the seasonal cycle of &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2 &lt;/sub&gt;at different measurement sites across the world.&lt;/p&gt;&lt;p&gt;The amplitude of the seasonal cycle of &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2 &lt;/sub&gt;is of particular importance to quantify land biosphere processes. The decreasing &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2 &lt;/sub&gt;of the atmosphere during the last decades (Suess effect) leads to a divergence of the &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C signature in assimilation and heterotrophic respiration, because of the long lifetime of soil pools. This is expected to lead to a high sensitivity of the seasonal amplitude to the amount of soil respiration. The effect of changes in soil turnover times on the simulated seasonal cycle is explored with factorial simulations of the Dynamic Global Vegetation Model LPX-Bern.&lt;/p&gt;

MAGNETOTELLURIC RESPONSE OF LATERALLY INHOMOGENEOUS AND ANISOTROPIC MEDIA

Geophysics ◽  
1975 ◽  
Vol 40 (6) ◽  
pp. 1035-1045 ◽  
Author(s):  
I. K. Reddy ◽  
D. Rankin
Keyword(s):  
Field Measurements ◽  
Complex Model ◽  
Dimensional Structure ◽  
Impedance Tensor ◽  
Two Dimensional ◽  
Galerkin Finite Element Method ◽  
Galerkin Finite Element ◽  
The Earth ◽  
Lateral Inhomogeneity ◽  
Anisotropic Conducting

The lack of agreement between magnetotelluric field measurements and the calculations based on essentially two‐dimensional models with either anisotropy or lateral inhomogeneity necessitates a more complex model of the earth than has been previously considered. The Galerkin finite‐element method is applied to a two‐dimensional structure with a tensor conductivity. The importance of considering conductivity as a tensor is illustrated by a model consisting of an anisotropic, conducting dike embedded in an anisotropic half‐space. This model can be distinguished from an isotropic model by the nonvanishing diagonal elements of the impedance tensor, the ellipticity indices, and the skew.

High sensitivity and quantitative magnetic field measurements at 600°C

2006 ◽  
Vol 99 (8) ◽  
pp. 08B302 ◽  
Author(s):  
Takuya Yamamura ◽  
Dai Nakamura ◽  
Masataka Higashiwaki ◽  
Toshiaki Matsui ◽  
Adarsh Sandhu
Keyword(s):  
Magnetic Field ◽  
High Sensitivity ◽  
Field Measurements ◽  
Magnetic Field Measurements

scholarly journals A novel instrument for measurements of BrO with LED based Cavity-Enhanced Differential Optical Absorption Spectoscopy

2013 ◽  
Vol 6 (4) ◽  
pp. 6047-6096
Author(s):  
D. J. Hoch ◽  
J. Buxmann ◽  
H. Sihler ◽  
D. Pöhler ◽  
C. Zetzsch ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Marine Boundary Layer ◽  
Detection Limits ◽  
High Sensitivity ◽  
Field Measurements ◽  
Reaction Chamber ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Polar Regions ◽  
Chamber Studies

Abstract. The chemistry of the troposphere and specifically the global tropospheric ozone budget is affected by reactive halogen species like Bromine monoxide (BrO) or Chlorine monoxide (ClO). Especially BrO plays an important role in the processes of ozone destruction, disturbance of NOx and HOx chemistry, oxidation of DMS, and the deposition of elementary mercury. In the troposphere BrO has been detected in polar regions, at salt lakes, in volcanic plumes, and in the marine boundary layer. For a better understanding of these processes field measurements as well as reaction-chamber studies are performed. In both cases instruments with high spatial resolution and high sensitivity are necessary. A Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument with an open path measurement cell was designed and applied. For the first time, a CE-DOAS instrument is presented using an UV-LED in the 325–365 nm wavelength range. In laboratory studies, BrO as well as HONO, HCHO, O3, and O4, could be reliable determined at detection limits of 20 ppt for BrO, 9.1 ppb for HCHO, 970 ppt for HONO, and 91 ppb for O3, for five minutes integration time, respectively. The best detection limits were achieved for BrO (11 ppt), HCHO (5.1 ppb), HONO (490 ppt), and O3 (59 ppb) for integration times of 81 min or less. Comparison with established White-System DOAS and O3 monitor demonstrate the reliability of the instrument.

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