scholarly journals Planetary fertility during the past 400 ka based on the triple isotope composition of O<sub>2</sub> in trapped gases from the Vostok ice core

2012 ◽  
Vol 8 (5) ◽  
pp. 1509-1526 ◽  
Author(s):  
T. Blunier ◽  
M. L. Bender ◽  
B. Barnett ◽  
J. C. von Fischer
Keyword(s):  
Isotope Exchange ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Ice Core ◽  
Fractionation Process ◽  
Factors Affecting ◽  
Mass Independent Fractionation ◽  
Oxygen Cycle ◽  
Steady State Model ◽  
O2 Production

Abstract. The productivity of the biosphere leaves its imprint on the isotopic composition of atmospheric oxygen. Ultimately, atmospheric oxygen, through photosynthesis, originates from seawater. Fractionations during the passage from seawater to atmospheric O2 and during respiration affect δ17O approximately half as much as δ18O. An "anomalous" (also termed mass independent) fractionation process changes δ17O about 1.7 times as much as δ18O during isotope exchange between O2 and CO2 in the stratosphere. The relative rates of biological O2 production and stratospheric processing determine the relationship between δ17O and δ18O of O2 in the atmosphere. Variations of this relationship thus allow us to estimate changes in the rate of O2 production by photosynthesis versus the rate of O2–CO2 isotope exchange in the stratosphere. However, the analysis of the 17O anomaly is complicated because each hydrological and biological process fractionates δ17O and δ18O in slightly different proportions. In this study we present O2 isotope data covering the last 400 ka (thousand years) from the Vostok ice core. We reconstruct oxygen productivities from the triple isotope composition of atmospheric oxygen with a box model. Our steady state model for the oxygen cycle takes into account fractionation during photosynthesis and respiration by the land and ocean biosphere, fractionation during the hydrologic cycle, and fractionation when oxygen passes through the stratosphere. We consider changes of fractionation factors linked to climate variations, taking into account the span of estimates of the main factors affecting our calculations. We find that ocean oxygen productivity was within 20% of the modern value throughout the last 400 ka. Given the presumed reduction in terrestrial oxygen productivity, the total oxygen production during glacials was likely reduced.

scholarly journals Planetary fertility during the past 400 ka based on the triple isotope composition of O<sub>2</sub> in trapped gases from the Vostok ice core

2012 ◽  
Vol 8 (1) ◽  
pp. 435-479
Author(s):  
T. Blunier ◽  
M. L. Bender ◽  
B. Barnett ◽  
J. C. von Fisher
Keyword(s):  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Ice Core ◽  
Co2 Exchange ◽  
Slight Reduction ◽  
Fractionation Process ◽  
Factors Affecting ◽  
Steady State Model ◽  
Mass Dependent ◽  
O2 Production

Abstract. The productivity of the biosphere leaves its imprint on the isotopic composition of atmospheric oxygen. Ultimately atmospheric oxygen, through photosynthesis, originates from seawater. Fractionations during the passage from seawater to atmospheric O2 and during respiration are mass dependent, affecting δ17O about half as much as δ18O. An "anomalous" (also termed mass independent) fractionation process changes δ17O about 1.7 times as much as δ18O during isotope exchange between O2 and CO2 in the stratosphere. The relative rates of biological O2 production and stratospheric processing determine the relationship between δ17O and δ18O of O2 in the atmosphere. Variations of this relationship thus allow us to estimate changes in the rate of mass dependent O2 production by photosynthesis vs. the rate of mass independent O2-CO2 exchange in the stratosphere. However, the analysis of the 17O anomaly is complicated because each hydrological and biological process influencing δ17O and δ18O fractionates 17O and 18O in slightly different proportions. In this study we present oxygen data covering the last 400 kyr from the Vostok ice core. We reconstruct oxygen productivities from the triple isotope composition of atmospheric oxygen with a box model. Our steady state model for the oxygen cycle takes into account fractionation during photosynthesis and respiration of the land and ocean biosphere as well as fractionation when oxygen passes through the stratosphere. We consider changes of fractionation factors linked to climate variations taking into account the span of estimates of the main factors affecting our calculations. We find that ocean oxygen productivity was likely elevated relative to modern during glacials. However, this increase probably did not fully compensate for a reduction in land ocean productivity resulting in a slight reduction in total oxygen production during glacials.

The effect of decationation of hydroxylated HNaY zeolites on their interaction with ethylene and propylene. hydrogen complexes, oligomeration and isotope exchange

1980 ◽  
Vol 45 (11) ◽  
pp. 3101-3115 ◽  
Author(s):  
Ludmila Kubelková ◽  
Jana Nováková ◽  
Zdeněk Dolejšek ◽  
Pavel Jírů
Keyword(s):  
Isotope Exchange ◽  
Decisive Role ◽  
Single Step ◽  
Hydroxyl Groups ◽  
Isotope Exchange Reaction ◽  
Factors Affecting ◽  
Step Mechanism ◽  
Formed Hydrogen ◽  
Lower Basicity ◽  
Multiple Step

The effect of decationation on the interaction of propylene and ethylene with the hydroxylated forms of HNaY zeolites has been studied. The compounds formed in the zeolite cavities were studied using their infrared spectra, the composition of the gaseous phase was followed by mass spectrometry. The results showed that among factors affecting the interaction with propylene properties of hydroxyl groups play the decisive role. With the increasing decationation of the zeolite the strength of the OH bond in the hydrogen complex of the large-cavity hydroxyls with propylene decreased and the rate of propylene oligomeration at 310 K as well as the isotope exchange rate of propylene-d6 with the zeolite hydroxyls at 570 K increased. The propylene isotope exchange reaction proceeded by the multiple-step mechanism. In the case of ethylene only the physical sorption with a non-specific character was observed at 310 K. The adsorbed amount increased with the increasing content of Na+ ions in the zeolite (with the decreasing decationation). A part of the adsorbed molecules formed hydrogen complexes with hydroxyls of large cavities. The observed lower weakening of the OH bond was in agreement with the lower basicity of ethylene if compared with propylene. The isotope exchange of ethylene-d4 with the zeolite hydroxyls proceeded by a single-step mechanism, it had an autocatalytic character and its rate was 70 times lower than that of the isotope exchange of propylene-d6 with OH.

Factors affecting 13C/12C ratios of inland halophytes. I. Controlled studies on growth and isotopic composition of Puccinellia nuttalliana

1986 ◽  
Vol 64 (11) ◽  
pp. 2693-2699 ◽  
Author(s):  
Robert D. Guy ◽  
David M. Reid ◽  
H. Roy Krouse
Keyword(s):  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Isotope Analysis ◽  
Research Problem ◽  
Carbon Isotope Composition ◽  
Stable Carbon ◽  
Factors Affecting ◽  
Plant Parts ◽  
High Level ◽  
Puccinellia Nuttalliana

Studies on various factors affecting the growth and stable carbon isotope composition of the graminaceous C3 halophyte Puccinellia nuttalliana (Schultes) Hitch. were initiated as a step towards interpreting δ13C variations in nature. For isotope analysis, combustion at 900 °C resulted in higher CO2 yield than at 550 °C but did not affect δ13C values. Differences in δ13C between leaves of different insertion level were unimportant, but roots were about 1‰ more positive than shoots. Trends in δ13C with salinity were the same in all plant parts. Depressions of growth by NaCl or Na2SO4 were similar, but plants grown in Na2SO4 displayed a greater shift in δ13C relative to controls. Growth rates were affected more by salinity than were previously reported photosynthetic rates. At typical salinities, δ13C changed linearly with salinity. The supply of nitrate to stressed and unstressed plants had no important influence on δ13C. Growth in polyethylene glycol produced δ13C values consistent with a high level of stress. After a salinity step-up, changes in δ13C were complete within 10 days. During winter, data were found to be heavily influenced by unintentional, human-respired CO2 enrichment. This represents a potentially serious research problem in laboratories of temperate climes.

Triple-isotope composition of atmospheric oxygen as a tracer of biosphere productivity

Nature ◽  
10.1038/22987 ◽  
1999 ◽  
Vol 400 (6744) ◽  
pp. 547-550 ◽  
Author(s):  
Boaz Luz ◽  
Eugeni Barkan ◽  
Michael L. Bender ◽  
Mark H. Thiemens ◽  
Kristie A. Boering
Keyword(s):  
Isotope Composition ◽  
Atmospheric Oxygen

scholarly journals Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation

2002 ◽  
Vol 35 ◽  
pp. 181-186 ◽  
Author(s):  
Alexey A. Ekaykin ◽  
Vladimir Ya. Lipenkov ◽  
Narcisse I. Barkov ◽  
Jean Robert Petit ◽  
Valerie Masson-Delmotte
Keyword(s):  
Isotope Composition ◽  
Ice Core ◽  
Snow Accumulation ◽  
Spatial And Temporal Variability ◽  
Weak Correlation ◽  
Ice Core Record ◽  
Vostok Station ◽  
The Mean ◽  
Mean Annual Air Temperature ◽  
Snow Samples

AbstractContinuous, detailed isotope (δD and δ18O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984– 2000. In addition, snow samples taken along the 1km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. the stacked δD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, ~102 years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.

scholarly journals Seasonal variations in nitrate isotope composition of three rivers draining into the North Sea

2010 ◽  
Vol 7 (4) ◽  
pp. 6051-6088 ◽  
Author(s):  
A. Deek ◽  
K. Emeis ◽  
U. Struck
Keyword(s):  
Isotopic Composition ◽  
North Sea ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Isotope Effects ◽  
Nitrate Sources ◽  
Particulate Nitrogen ◽  
Soil Nitrification ◽  
Mean Values ◽  
Δ 15N

Abstract. Nitrate loading of coastal ecosystems by rivers that drain industrialised catchments continues to be a problem in the South Eastern North Sea, in spite of significant mitigation efforts over the last 2 decades. To identify nitrate sources, sinks, and turnover in three German rivers that discharge into the German Bight, we determined δ 15N-NO3- and δ18O- NO3- in nitrate and δ 15N of particulate nitrogen for the period 2006–2009 (biweekly samples). The nitrate loads of Rhine, Weser and Ems varied seasonally in magnitude and δ 15N-NO3- (6.5–21‰), whereas the δ 18O-NO3- (-0.3–5.9‰) and δ 15N-PN (4–14‰) were less variable. Overall temporal patterns in nitrate mass fluxes and isotopic composition suggest that a combination of nitrate delivery from nitrification of soil ammonia in the catchment and assimilation of nitrate in the rivers control the isotopic composition of nitrate. Nitrification in soils as a source is indicated by low δ 18O-NO3- in winter, which traces the δ 18O of river water. Mean values of δ 18O-H2O were between –9.4‰ and –7.3‰; combined in a ratio of 2:1 with the atmospheric oxygen δ 18O of 23.5‰ agrees with the found δ 18O of nitrate in the rivers. Parallel variations of δ 15N-NO3- and δ 18O-NO3- within each individual river are caused by isotope effects associated with nitrate assimilation in the water column, the extent of which is determined by residence time in the river. Assimilation is furthermore to some extent mirrored both by the δ 15N of nitrate and particulate N. Although δ 15-NO3- observed in Rhine, Weser and Ems are reflected in high average δ 15N-PN (between 6‰ and 9‰, both are uncorrelated in the time series due to lateral and temporal mixing of PN. That a larger enrichment was consistently seen in δ 15N-NO3- relative to δ 18O-NO3- is attributed to constant additional diffuse nitrate inputs deriving from soil nitrification in the catchment area. A statistically significant inverse correlation exists between increasing δ 15N-NO3- values and decreasing NO3- concentrations. This inverse relationship – observed in each seasonal cycle – together with a robust relationship between human dominated land use and δ 15N-NO3- values demonstrates a strong influence of human activities and riverine nitrate consumption efficiency on the isotopic composition of riverine nitrate.

Global biosphere primary productivity over the last 800,000 years reconstructed from the triple-isotope composition of dioxygen trapped in polar ice cores

2021 ◽  
Author(s):  
Ji-Woong Yang ◽  
Amaëlle Landais ◽  
Margaux Brandon ◽  
Thomas Blunier ◽  
Frédéric Prié ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Ice Cores ◽  
Oxygenic Photosynthesis ◽  
Time Interval ◽  
Polar Ice ◽  
Future Evolution ◽  
Glacial Stage ◽  
Glacial Periods

&lt;p&gt;The primary production, or oxygenic photosynthesis of the global biosphere, is one of the main source and sink of atmospheric oxygen (O&lt;sub&gt;2&lt;/sub&gt;) and carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;), respectively. There has been a growing number of evidence that global gross primary productivity (GPP) varies in response to climate change. It is therefore important to understand the climate- and/or environment controls of the global biosphere primary productivity for better predicting the future evolution of biosphere carbon uptake. The triple-isotope composition of O&lt;sub&gt;2&lt;/sub&gt; (&amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of O&lt;sub&gt;2&lt;/sub&gt;) trapped in polar ice cores allows us to trace the past changes of global biosphere primary productivity as far back as 800,000 years before present (800 ka). Previously available &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of O&lt;sub&gt;2&lt;/sub&gt; records over the last ca. 450 ka show relatively low and high global biosphere productivity over the last five glacial and interglacial intervals respectively, with a unique pattern over Termination V (TV) - Marine Isotopic Stage (MIS) 11, as biosphere productivity at the end of TV is ~ 20 % higher than the four younger ones (Blunier et al., 2012; Brandon et al., 2020). However, questions remain on (1) whether the concomitant changes of global biosphere productivity and CO&lt;sub&gt;2&lt;/sub&gt; were the pervasive feature of glacial periods over the last 800 ka, and (2) whether the global biosphere productivity during the &amp;#8220;lukewarm&amp;#8221; interglacials before the Mid-Brunhes Event (MBE) were lower than those after the MBE.&lt;br&gt;Here, we present an extended composite record of &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of O&lt;sub&gt;2&lt;/sub&gt; covering the last 800 ka, based on new &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of O&lt;sub&gt;2&lt;/sub&gt; results from the EPICA Dome C and reconstruct the evolution of global biosphere productivity over that time interval using the independent box models of Landais et al. (2007) and Blunier et al. (2012). We find that the glacial productivity minima occurred nearly synchronously with the glacial CO&lt;sub&gt;2&lt;/sub&gt; minima at mid-glacial stage; interestingly millennia before the sea level reaches their minima. Following the mid-glacial minima, we also show slight productivity increases at the full-glacial stages, before deglacial productivity rises. Comparison of reconstructed interglacial productivity demonstrates a slightly higher productivity over the post-MBE (MISs 1, 5, 7, 9, and 11) than pre-MBE ones (MISs 13, 15, 17, and 19). However, the mean difference between post- and pre-MBE interglacials largely depends on the box model used for productivity reconstruction.&lt;/p&gt;

scholarly journals Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem

2018 ◽  
Vol 115 (26) ◽  
pp. 6602-6607 ◽  
Author(s):  
Uri Ryb ◽  
John M. Eiler
Keyword(s):  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Isotope Composition ◽  
Temporal Variations ◽  
Oxygen Isotope Exchange ◽  
Diagenetic Alteration ◽  
Isotope Studies ◽  
Dolomite Problem ◽  
Clumped Isotope

The18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and ‟clumped” isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15–158 °C and parent waters having δ18OVSMOWvalues from −2 to +12‰. These data are consistent with dolomitization through sediment/rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen–isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

Sign in / Sign up

Export Citation Format

Share Document