17O18O and 18O18O in ice core O2 from Greenland: implications to reconstruct past atmospheric photochemistry

2020 ◽  
Author(s):  
Amzad Laskar ◽  
Rahul Peethambaran ◽  
Sergey Gromov ◽  
Thomas Blunier ◽  
Thomas Roeckmann
Keyword(s):  
Ice Core ◽  
Stable Isotope Ratio ◽  
Transport Processes ◽  
Dynamic Simulations ◽  
Atmospheric Photochemistry ◽  
Measurement Results ◽  
Isotope Ratio Mass Spectrometer ◽  
Dominant Process ◽  
Ozone Photochemistry ◽  
Explicit Dynamic

<p>Abundances of <sup>17</sup>O<sup>18</sup>O and <sup>18</sup>O<sup>18</sup>O (also called clumped isotopes and denoted by Δ<sub>35</sub> and Δ<sub>36</sub>) of O<sub>2</sub>  in firn and ice core air are novel tracers that can be useful to study past changes in atmospheric photochemistry and temperature. We present Δ<sub>35</sub> and Δ<sub>36</sub> values measured in firn and ice core air O<sub>2</sub> from North Greenland (NEEM; 77.45°N 51.06°W). The aim is to reconstruct the preindustrial-industrial, Holocene and glacial-interglacial variation in the tropospheric ozone photochemistry and temperature. Measurements of Δ<sub>35</sub> and Δ<sub>36</sub> are carried out using a high-resolution stable isotope ratio mass spectrometer Thermo Fisher 253 ULTRA[1]. Our measurements of Δ<sub>35</sub> and Δ<sub>36</sub>  across past air, from archive samples, to the modern-day show significant changes in the atmospheric photochemistry via ozone burdening and stratospheric- tropospheric transport processes. We will present the measurement results along with a detailed discussion on the dominant process using explicit dynamic simulations of ∆<sub>36 </sub>in the AC-GCM EMAC model [2,3,4].</p><p> </p>

scholarly journals Impact of precipitation intermittency on NAO-temperature signals in proxy records

2013 ◽  
Vol 9 (2) ◽  
pp. 871-886 ◽  
Author(s):  
M. Casado ◽  
P. Ortega ◽  
V. Masson-Delmotte ◽  
C. Risi ◽  
D. Swingedouw ◽  
...  
Keyword(s):  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ice Cores ◽  
Stable Isotope Ratio ◽  
Global Network ◽  
Temporal Correlations ◽  
The North ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract. In mid and high latitudes, the stable isotope ratio in precipitation is driven by changes in temperature, which control atmospheric distillation. This relationship forms the basis for many continental paleoclimatic reconstructions using direct (e.g. ice cores) or indirect (e.g. tree ring cellulose, speleothem calcite) archives of past precipitation. However, the archiving process is inherently biased by intermittency of precipitation. Here, we use two sets of atmospheric reanalyses (NCEP (National Centers for Environmental Prediction) and ERA-interim) to quantify this precipitation intermittency bias, by comparing seasonal (winter and summer) temperatures estimated with and without precipitation weighting. We show that this bias reaches up to 10 °C and has large interannual variability. We then assess the impact of precipitation intermittency on the strength and stability of temporal correlations between seasonal temperatures and the North Atlantic Oscillation (NAO). Precipitation weighting reduces the correlation between winter NAO and temperature in some areas (e.g. Québec, South-East USA, East Greenland, East Siberia, Mediterranean sector) but does not alter the main patterns of correlation. The correlations between NAO, δ18O in precipitation, temperature and precipitation weighted temperature are investigated using outputs of an atmospheric general circulation model enabled with stable isotopes and nudged using reanalyses (LMDZiso (Laboratoire de Météorologie Dynamique Zoom)). In winter, LMDZiso shows similar correlation values between the NAO and both the precipitation weighted temperature and δ18O in precipitation, thus suggesting limited impacts of moisture origin. Correlations of comparable magnitude are obtained for the available observational evidence (GNIP (Global Network of Isotopes in Precipitation) and Greenland ice core data). Our findings support the use of archives of past δ18O for NAO reconstructions.

Detecting Transition in Flat Plate Flow With Laser Interferometric Vibrometry (LIV)

2016 ◽  
Author(s):  
Pascal Bader ◽  
Wolfgang Sanz ◽  
Johannes Peterleithner ◽  
Jakob Woisetschläger ◽  
Franz Heitmeir ◽  
...  
Keyword(s):  
Flat Plate ◽  
Measurement Techniques ◽  
Transitional Zone ◽  
Transport Processes ◽  
Transitional Region ◽  
Test Cases ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Measurement Results ◽  
Laser Interferometric

Flow in turbomachines is generally highly turbulent. The boundary layers, however, often exhibit laminar-to-turbulent transition. Relaminarization from turbulent to laminar flow may also occur. The state of the boundary layer is important since it strongly influences transport processes like skin friction and heat transfer. It is therefore vitally important for the designer to understand the process of laminar-to-turbulent transition and to determine the position of transition onset and the length of the transitional region. In order to better understand transition and relaminarization it is helpful to study simplified test cases first. Therefore, in this paper the flow along a flat plate is experimentally studied to investigate laminar-to-turbulent transition. Measurements were performed for the different free-stream velocities of 5 m/s and 10 m/s. Several measurement techniques were used in order to reliably detect the transitional zone: the Preston tube, hot wire anemometry, thermography and Laser Interferometric Vibrometry (LIV). The first two measurement techniques are extensively in use at the institute ITTM and by other research groups. They are therefore used as a reference for validating the LIV measurement results. An advantage of the LIV technique is that it does not need any seeding of the fluid and that it is non-intrusive. Therefore this measurement technique does not influence the flow, and it can be used in narrow flow passages since there is no blockage, in contrast to probe-based measurement techniques. Further to the measurements, computational simulations were performed with the Fluent® and CFX® codes from ANSYS®, as well as with the in-house code Linars. The Menter SST k-ω turbulence model with the γ-ReΘ transition model was used in order to test its capability to predict the laminar-to-turbulent transition.

scholarly journals Bidirectional permeability measurements of polar firn

2002 ◽  
Vol 35 ◽  
pp. 63-66 ◽  
Author(s):  
Gina L. Luciano ◽  
Mary R. Albert
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Free Path Length ◽  
Mean Free Path ◽  
Transport Processes ◽  
Climate History ◽  
Chemical Modeling ◽  
Vertical Permeability ◽  
Ice Core Record ◽  
Sphere Radius

AbstractIce cores provide a valuable archive of climate history. for a complete understanding of this archive, it is important to understand air–snow exchange processes through the snow and firn in order to fully decode the ice-core record. Transport processes through the snow and firn are dependent upon their physical properties. In this paper, bidirectional permeabilities from selected sections of a 13 mcore from Summit, Greenland, are presented. Differences between lateral and vertical permeabilities are evident throughout the core in permeameter data and in microstructure statistics. Both lateral and vertical permeabilities are consistent with overall patterns of previous polar permeability data with depth. the differences between lateral and vertical permeability measurements for some samples can be attributed to equivalent sphere radius. Further studies examining mean free-path length may be helpful in chemical modeling and in deriving an equation relating permeability to microstructure.

scholarly journals The influence of layering and barometric pumping on firn air transport in a 2-D model

2018 ◽  
Vol 12 (6) ◽  
pp. 2021-2037 ◽  
Author(s):  
Benjamin Birner ◽  
Christo Buizert ◽  
Till J. W. Wagner ◽  
Jeffrey P. Severinghaus
Keyword(s):  
Dispersion Model ◽  
Noble Gas ◽  
Ice Core ◽  
Transport Processes ◽  
Air Transport ◽  
Atmospheric Composition ◽  
Elemental Ratios ◽  
Barometric Pumping ◽  
Kinetic Fractionation ◽  
D Model

Abstract. Ancient air trapped in ice core bubbles has been paramount to developing our understanding of past climate and atmospheric composition. Before air bubbles become isolated in ice, the atmospheric signal is altered in the firn column by transport processes such as advection and diffusion. However, the influence of low-permeability layers and barometric pumping (driven by surface pressure variability) on firn air transport is not well understood and is not readily captured in conventional one-dimensional (1-D) firn air models. Here we present a two-dimensional (2-D) trace gas advection–diffusion–dispersion model that accounts for discontinuous horizontal layers of reduced permeability. We find that layering or barometric pumping individually yields too small a reduction in gravitational settling to match observations. In contrast, when both effects are active, the model's gravitational fractionation is suppressed as observed. Layering focuses airflows in certain regions in the 2-D model, which acts to amplify the dispersive mixing resulting from barometric pumping. Hence, the representation of both factors is needed to obtain a realistic emergence of the lock-in zone. In contrast to expectations, we find that the addition of barometric pumping in the layered 2-D model does not substantially change the differential kinetic fractionation of fast- and slow-diffusing trace gases. Like 1-D models, the 2-D model substantially underestimates the amount of differential kinetic fractionation seen in actual observations, suggesting that further subgrid-scale processes may be missing in the current generation of firn air transport models. However, we find robust scaling relationships between kinetic isotope fractionation of different noble gas isotope and elemental ratios. These relationships may be used to correct for kinetic fractionation in future high-precision ice core studies and can amount to a bias of up to 0.45 °C in noble-gas-based mean ocean temperature reconstructions at WAIS Divide, Antarctica.

scholarly journals Holocene electrical and chemical measurements from the EPICA–Dome C ice core

2000 ◽  
Vol 30 ◽  
pp. 20-26 ◽  
Author(s):  
R. Udisti ◽  
S. Becagli ◽  
E. Castellano ◽  
R. Mulvaney ◽  
J. Schwander ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Conductivity Measurement ◽  
Progressive Increase ◽  
Snow Accumulation ◽  
Transport Processes ◽  
Ionic Balance ◽  
Volcanic Emissions ◽  
Relative Contribution ◽  
Chloride Profiles

AbstractThe comparison between electric (electric-conductivity measurement (ECM) and dielectric profiling (DEP)) and chemical sulphate and chloride) depth profiles along the first 400 m of the EPICA-Dome C ice core revealed a very good fit, especially for peaks related to volcanic emissions. From the comparison between these profiles, a dominant contribution of sulphuric acid to the ionic balance of Antarctic ice for the Holocene was confirmed. A progressive increase with depth was observed for chloride concentrations, showing a change of relative contribution between sulphate and chloride. A higher increase of chloride was evident between 270 and 360 m depth, probably due to a change in source or transport processes or to an increase of the annual snow-accumulation rate. The DEP, ECM and sulphate ice signatures of Tambora (AD 1816) and El Chichon (?) (AD 1259) eruptions are described in detail. A characteristic peak series, due to HCl deposition, was identified at 103–109 m depth from the ECM, DEP and chloride profiles.

scholarly journals ЗОЛОТО-СУЛЬФИДНО-КВАРЦЕВОЕ РУДОПРОЯВЛЕНИЕ ХААК-САИР (ЗАПАДНАЯ ТУВА): ВОЗРАСТ, PT-ПАРАМЕТРЫ, СОСТАВ ФЛЮИДОВ, ИЗОТОПИЯ S, O И С

2021 ◽  
Vol 332 (12) ◽  
pp. 148-163
Author(s):  
Ренат Васильевич Кужугет ◽  
Наталья Николаевна Анкушева ◽  
Чаяна Олекоевна Кадыр-оол ◽  
Анна Андреевна Редина ◽  
Илья Романович Прокопьев ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Mass Spectrometer ◽  
Isotope Ratio ◽  
Stable Isotope Ratio ◽  
Icp Ms ◽  
Isotope Ratio Mass Spectrometer

Ссылка для цитирования: Золото-сульфидно-кварцевое рудопроявление Хаак-Саир (Западная Тува): возраст, PT-параметры, состав флюидов, изотопия S, O и С / Р.В. Кужугет, Н.Н. Анкушева, Ч.О. Кадыр-оол, А.А. Редина, И.Р. Прокопьев, А.В. Пономарчук // Известия Томского политехнического университета. Инжиниринг георесурсов. – 2021. – Т. 332. – № 12. – С. 148-163. Актуальность исследования обусловлена необходимостью определения возраста и условий образования золото-кварцевого рудопроявления Хаак-Саир в лиственитах, характеризующегося своеобразным минеральным составом руд, выраженным в наличии ртутистого золота, селенидов (фишессерита, науманнита, тиманнита, клаусталита) и теллуридов (гессита, теллуровисмутита и колорадоита). Цель: определение возраста, условий образования, геохимических особенностей рудоносного флюида и его источников, золото-кварцевого рудопроявления Хаак-Саир в Западной Туве. Методы. Оптические исследования руд проведены на микроскопах Olympus BX41 и ПОЛАМ П-213М. Состав минералов определен с помощью сканирующего электронного микроскопа MIRA 3 LMU с ЭДС Oxford Instruments Nanoanalysis Ltd. Температуры, солевой состав, концентрации солей и давление при минералообразовании получены по индивидуальным флюидным включениям с использованием термокамеры Linkam TMS-600 и оптического микроскопа Olympus BX 51; газовый состав флюидных включений определен на рамановском спектрометре Ramanor U-1000 с детектором Horiba DU420E-OE-323, лазер Millennia Pro (Spectra-Physics); валовый газовый состав флюида диагностирован на газовом хроматографе Agilent 6890, содержания анионов в вытяжке проанализированы на жидкостном хроматографе ЦВЕТ-3000, катионы и микроэлементы – методом ICP MS (Elan-6100); соотношения δ34S в галените определены на газовом масс-спектрометре Finnigan™ MAT Delta в режиме двойного напуска (аналитики В.Н. Реутский, М.Н. Колбасова, ИГМ СО РАН); соотношения стабильных изотопов δ18С и δ18О в кварце и карбонатах определены на масс-спектрометрах Stable Isotope Ratio Mass Spectrometer Finnigan™ MAT 253 с пробоотборником Finnigan GasBench II и стандартами IAEA: NBS-18 и NBS-19 (аналитик А.Н. Пыряев, ИГМ СО РАН) и Isoprime с AQS (Akita Quartz Standard, аналитики Х. Каварая, О. Мацубая, Университет г. Акита), соответственно; 40Ar/39Ar датирование проведено методом ступенчатого прогрева. Результаты. Установленный 40Ar/39Ar методом возраст синрудных лиственитов рудопроявления составляет 379,4±4,4 млн лет, что соответствует позднему девону. Термометрическими исследованиями установлено, что вмещающие листвениты рудопроявления образовались при участии водного Na-K-хлоридного флюида с соленостью 3,4–6,5 мас. % NaСl-экв. и температурами не менее 325–200 °C. Золото-сульфидно-кварцевые жилы отлагались при P~0,5–0,75 кбар (~1,5–2,3 км) из углекислотно-водно-хлоридного (Na-K ± Fe) флюида, содержащего CH4 с концентрациями солей 4,5–37,4 мас. % NaСl-экв. при снижении температур от 320 до 120 °C (I рудная стадия – 310–200 °С, II рудная стадия – 320–120 °С) и вариациях f O2, f S2, f Se2 и f Te2, которые обусловили разнообразие минеральных форм Au, Ag и Hg. Величины δ34S галенита изменяются от –0,6 до –0,4 ‰, а вычисленные значения δ34SH2S флюида I рудной стадии находятся в интервале +1,5...+2,1 ‰ (T=280–210 °C), II рудной стадии – +1,6...+2,6 ‰ (T=290–190 °C), что свидетельствует о магматическом происхождении серы. Значения δ18О в кварце рудных жил изменяются от 17,0 до 17,4 ‰, доломите – +17,4...+17,8 ‰, кальците – +16,5 ‰, рассчитанные значения δ18ОH2S флюида I рудной стадии находятся в интервале +8,1...+5,7 ‰ (T=250–210 °C), II рудной стадии – +6,7...–2,2 ‰ (T=230–120 °C) позволили предположить, что на ранних стадиях рудообразующего процесса флюид имел магматическое происхождение, а на поздних смешивался с метеорными водами. Величины δ13C в доломите I рудной стадии варьируют от –0,4 до –0,7 ‰; в кальците II рудной стадии – –0,3 ‰, а рассчитанные значения δ13C во флюиде находятся в интервале –1,2...+0,1 ‰ (T=250–210 °C) и –3,3...+0,5 ‰ (T=230–120 °C), соответственно. Это предполагает поступление углерода из гранитоидных магм и/или заимствование его из вмещающих пород. Состав флюида трансформировался от ранних стадий к поздним от углекислотно-водно-хлоридного до водно-хлоридного с уменьшением концентраций хлоридов щелочных и щелочноземельных металлов (от 37,4 до 4 мас. % NaCl-экв.).

scholarly journals The Effect of Abrasive Particles Movement on Deburring Effectiveness in REMF Process by using Explicit Dynamic Simulations

2021 ◽  
Author(s):  
Jung-Hee Lee ◽  
Se-Yeong Lee ◽  
Jae-Seob Kwak
Keyword(s):  
Rotational Velocity ◽  
Particle Diameter ◽  
Impact Angle ◽  
Dynamic Simulations ◽  
Machined Surface ◽  
Pareto Analysis ◽  
High Productivity ◽  
Process Factors ◽  
Electro Magnetic ◽  
Explicit Dynamic

Abstract The main aim of this study was to suggest rotating electro-magnetic finishing(REMF) which had the capability to yield ultra-fine finished surface in micro-meter level with high productivity in a short time. The performance of the REMF process was primarily dependent upon magnetic and impact energy by the physical properties of a particle, particle velocity, and impact angle. Therefore, in this study, numerical simulations were conducted by explicit dynamic analysis to verify the effect of both single and multiple abrasive media impact characteristics on a deburring area of the machined surface. Based on the observed results and Pareto analysis, it was found that the overall weight of the particles was the most significantly affected for burr reduction, and deburring area was proportional to the increasing impact angle as well. In addition, to estimate the relationship between process factors and output variable and determine the optimum condition for burr reduction, a second-order polynomial model was developed by adopting a response surface methodology. As a result, the predictive model agreed with numerical analyzed results with 84.4% of the accuracy rate. The optimized deburring area was 2.27mm2 at 1,800rpm of rotational velocity, 0.7mm of particle diameter, and 2.0kg of total particle weight. It was founded to be similar to the maximum deburring area, about 2.37mm2, obtained from the simulations at the same condition.

scholarly journals Analysis of conservative tracer measurement results inside a planted horizontal subsurface flow constructed wetland filled with coarse gravel using Frechet distribution

2020 ◽  
Author(s):  
Ernő Dittrich ◽  
Mihály Klincsik ◽  
Dávid Somfai ◽  
Anita Dolgos-Kovács ◽  
Tibor Kiss ◽  
...  
Keyword(s):  
Subsurface Flow ◽  
Distribution Functions ◽  
Transport Processes ◽  
Response Curves ◽  
Fréchet Distribution ◽  
Measurement Results ◽  
Research Outcome ◽  
Horizontal Subsurface Flow ◽  
Frechet Distribution ◽  
Coarse Gravel

Abstract We worked out a method in Maple environment to help understand the difficult transport processes in horizontal subsurface flow constructed wetlands filled with coarse gravel (HSFCW-C). With this process, the measured tracer results of the inner points of a HSFCW-C can be fitted more accurately than with the conventionally used distribution functions (Gaussian, Lognormal, Fick (Inverse Gaussian) and Gamma). This research outcome only applies for planted HSFCW-Cs. The outcome of the analysis shows that conventional solutions completely stirred series tank reactor (CSTR) model and convection-dispersion transport (CDT) model do not describe the internal transport processes with sufficient accuracy. This study may help us develop better process descriptions of very complex transport processes in HSFCW-Cs. Our results also revealed that the tracer response curves of planted HSFCW-C conservative inner points can be fitted well with Frechet distribution only if the response curve has one peak.

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