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Oxygen isotope ratio cycle

January 01, 1970

Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples, measured with the isotope fractionation. The ratio is linked to ancient ocean temperature which in turn reflects ancient climate. Cycles in the ratio mirror climate changes in the geological history of Earth.

O-18 concentration versus time

Isotopes of oxygen edit

Oxygen (chemical symbol O) has three naturally occurring isotopes: 16O, 17O, and 18O, where the 16, 17 and 18 refer to the atomic mass. The most abundant is 16O, with a small percentage of 18O and an even smaller percentage of 17O. Oxygen isotope analysis considers only the ratio of 18O to 16O present in a sample.

The calculated ratio of the masses of each present in the sample is then compared to a standard, which can yield information about the temperature at which the sample was formed - see Proxy (climate) for details.

Connection between isotopes and temperature/weather edit

18O is two neutrons heavier than 16O and causes the water molecule in which it occurs to be heavier by that amount. The additional mass changes the hydrogen bonds so that more energy is required to vaporize H218O than H216O, and H218O liberates more energy when it condenses. In addition, H216O tends to diffuse more rapidly.

Because H216O requires less energy to vaporize, and is more likely to diffuse to the liquid phase, the first water vapor formed during evaporation of liquid water is enriched in H216O, and the residual liquid is enriched in H218O. When water vapor condenses into liquid, H218O preferentially enters the liquid, while H216O is concentrated in the remaining vapor.

As an air mass moves from a warm region to a cold region, water vapor condenses and is removed as precipitation. The precipitation removes H218O, leaving progressively more H216O-rich water vapor. This distillation process causes precipitation to have lower 18O/16O as the temperature decreases. Additional factors can affect the efficiency of the distillation, such as the direct precipitation of ice crystals, rather than liquid water, at low temperatures.

Due to the intense precipitation that occurs in hurricanes, the H218O is exhausted relative to the H216O, resulting in relatively low 18O/16O ratios. The subsequent uptake of hurricane rainfall in trees, creates a record of the passing of hurricanes that can be used to create a historical record in the absence of human records.[1]

In laboratories, the temperature, humidity, ventilation and so on affect the accuracy of oxygen isotope measurements.[2] Solid samples (organic and inorganic) for oxygen isotope measurements are usually stored in silver cups and measured with pyrolysis and mass spectrometry. Researchers need to avoid improper or prolonged storage of the samples for accurate measurements.[2]

Connection between temperature and climate edit

The 18O/16O ratio provides a record of ancient water temperature. Water 10 to 15 °C (18 to 27 °F) cooler than present represents glaciation. As colder temperatures spread toward the equator, water vapor rich in 18O preferentially rains out at lower latitudes. The remaining water vapor that condenses over higher latitudes is subsequently rich in 16O.[3] Precipitation and therefore glacial ice contain water with a low 18O content. Since large amounts of 16O water are being stored as glacial ice, the 18O content of oceanic water is high. Water up to 5 °C (9 °F) warmer than today represents an interglacial, when the 18O content of oceanic water is lower. A plot of ancient water temperature over time indicates that climate has varied cyclically, with large cycles and harmonics, or smaller cycles, superimposed on the large ones. This technique has been especially valuable for identifying glacial maxima and minima in the Pleistocene.

Connection between calcite and water edit

Limestone is deposited from the calcite shells of microorganisms. Calcite, or calcium carbonate, chemical formula CaCO3, is formed from water, H2O, and carbon dioxide, CO2, dissolved in the water. The carbon dioxide provides two of the oxygen atoms in the calcite. The calcium must rob the third from the water. The isotope ratio in the calcite is therefore the same, after compensation, as the ratio in the water from which the microorganisms of a given layer extracted the material of the shell. A higher abundance of 18O in calcite is indicative of colder water temperatures, since the lighter isotopes are all stored in the glacial ice. The microorganism most frequently referenced for identifying marine isotope stages is foraminifera.[4]

Research edit

Earth's dynamic oxygenation evolution is recorded in ancient sediments from the Republic of Gabon from between about 2,150 and 2,080 million years ago. Responsible for these fluctuations in oxygenation were likely driven by the Lomagundi carbon isotope excursion.[5]

See also edit

References edit

  1. ^ Miller, Dana L.; Mora, Claudia I.; Grissino-Mayer, Henri D.; Mock, Cary J.; Uhle, Maria E.; Sharp, Zachary (July 31 – September 19, 2006). "Tree-ring isotope records of tropical cyclone activity". Proceedings of the National Academy of Sciences, 2006 - National Acad Sciences. Vol. 103. National Acad Sciences. pp. 14294–14297. doi:10.1073/pnas.0606549103. PMC 1570183. Retrieved 2009-11-11.
  2. ^ a b Tsang, Man-Yin; Yao, Weiqi; Tse, Kevin (2020). Kim, Il-Nam (ed.). "Oxidized silver cups can skew oxygen isotope results of small samples". Experimental Results. 1: e12. doi:10.1017/exp.2020.15. ISSN 2516-712X.
  3. ^ "Paleoclimatology: The Oxygen Balance". Nasa Earth Observatory. 2005-05-06. Retrieved 2012-02-27.
  4. ^ Zeebe, Richard E. (1999). "An explanation of the effect of seawater carbonate concentration on foraminiferal oxygen isotopes". Geochimica et Cosmochimica Acta. 63 (13–14): 2001–2007. Bibcode:1999GeCoA..63.2001Z. doi:10.1016/S0016-7037(99)00091-5.
  5. ^ Timothy W. Lyons; Christopher T. Reinhard; Noah J. Planavsky (2014). "Atmospheric oxygenation three billion years ago". Nature. 506 (7488): 307–315. Bibcode:2014Natur.506..307L. doi:10.1038/nature13068. PMID 24553238. S2CID 4443958.
    • "The ups and downs of early atmospheric oxygen". ScienceDaily (Press release). February 19, 2014.
  • Encyclopædia Britannica under Climate and Weather, Pleistocene Climatic Change
  • Craig Harmon (1961). "Isotopic variations in meteoric waters". Science. 133 (3465): 1702–1703. Bibcode:1961Sci...133.1702C. doi:10.1126/science.133.3465.1702. PMID 17814749. S2CID 34373069.
  • Epstein S.; Mayeda T. (1953). "Variation of O18 content of waters from natural sources". Geochimica et Cosmochimica Acta. 4 (5): 213–224. Bibcode:1953GeCoA...4..213E. doi:10.1016/0016-7037(53)90051-9.
  • Veizer Ján; Godderis Yves; François Louis M (2000). (PDF). Nature. 408 (6813): 698–701. Bibcode:2000Natur.408..698V. doi:10.1038/35047044. PMID 11130067. S2CID 4372892. Archived from the original (PDF) on 2013-10-06. Retrieved 2014-10-23.

External links edit

  • NASA Earth Observatory: The Oxygen Balance
  • Scripps O2 Global Oxygen Measurements

January 01, 1970
oxygen, isotope, ratio, cycle, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, june, 2008, learn, when, remove, this, message,. This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations June 2008 Learn how and when to remove this message Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances such as polar ice or calcite in ocean core samples measured with the isotope fractionation The ratio is linked to ancient ocean temperature which in turn reflects ancient climate Cycles in the ratio mirror climate changes in the geological history of Earth O 18 concentration versus time Contents 1 Isotopes of oxygen 2 Connection between isotopes and temperature weather 3 Connection between temperature and climate 4 Connection between calcite and water 5 Research 6 See also 7 References 8 External linksIsotopes of oxygen editOxygen chemical symbol O has three naturally occurring isotopes 16O 17O and 18O where the 16 17 and 18 refer to the atomic mass The most abundant is 16O with a small percentage of 18O and an even smaller percentage of 17O Oxygen isotope analysis considers only the ratio of 18O to 16O present in a sample The calculated ratio of the masses of each present in the sample is then compared to a standard which can yield information about the temperature at which the sample was formed see Proxy climate for details Connection between isotopes and temperature weather edit18O is two neutrons heavier than 16O and causes the water molecule in which it occurs to be heavier by that amount The additional mass changes the hydrogen bonds so that more energy is required to vaporize H218O than H216O and H218O liberates more energy when it condenses In addition H216O tends to diffuse more rapidly Because H216O requires less energy to vaporize and is more likely to diffuse to the liquid phase the first water vapor formed during evaporation of liquid water is enriched in H216O and the residual liquid is enriched in H218O When water vapor condenses into liquid H218O preferentially enters the liquid while H216O is concentrated in the remaining vapor As an air mass moves from a warm region to a cold region water vapor condenses and is removed as precipitation The precipitation removes H218O leaving progressively more H216O rich water vapor This distillation process causes precipitation to have lower 18O 16O as the temperature decreases Additional factors can affect the efficiency of the distillation such as the direct precipitation of ice crystals rather than liquid water at low temperatures Due to the intense precipitation that occurs in hurricanes the H218O is exhausted relative to the H216O resulting in relatively low 18O 16O ratios The subsequent uptake of hurricane rainfall in trees creates a record of the passing of hurricanes that can be used to create a historical record in the absence of human records 1 In laboratories the temperature humidity ventilation and so on affect the accuracy of oxygen isotope measurements 2 Solid samples organic and inorganic for oxygen isotope measurements are usually stored in silver cups and measured with pyrolysis and mass spectrometry Researchers need to avoid improper or prolonged storage of the samples for accurate measurements 2 Connection between temperature and climate editThe 18O 16O ratio provides a record of ancient water temperature Water 10 to 15 C 18 to 27 F cooler than present represents glaciation As colder temperatures spread toward the equator water vapor rich in 18O preferentially rains out at lower latitudes The remaining water vapor that condenses over higher latitudes is subsequently rich in 16O 3 Precipitation and therefore glacial ice contain water with a low 18O content Since large amounts of 16O water are being stored as glacial ice the 18O content of oceanic water is high Water up to 5 C 9 F warmer than today represents an interglacial when the 18O content of oceanic water is lower A plot of ancient water temperature over time indicates that climate has varied cyclically with large cycles and harmonics or smaller cycles superimposed on the large ones This technique has been especially valuable for identifying glacial maxima and minima in the Pleistocene Connection between calcite and water editLimestone is deposited from the calcite shells of microorganisms Calcite or calcium carbonate chemical formula CaCO3 is formed from water H2O and carbon dioxide CO2 dissolved in the water The carbon dioxide provides two of the oxygen atoms in the calcite The calcium must rob the third from the water The isotope ratio in the calcite is therefore the same after compensation as the ratio in the water from which the microorganisms of a given layer extracted the material of the shell A higher abundance of 18O in calcite is indicative of colder water temperatures since the lighter isotopes are all stored in the glacial ice The microorganism most frequently referenced for identifying marine isotope stages is foraminifera 4 Research editEarth s dynamic oxygenation evolution is recorded in ancient sediments from the Republic of Gabon from between about 2 150 and 2 080 million years ago Responsible for these fluctuations in oxygenation were likely driven by the Lomagundi carbon isotope excursion 5 See also editd18O Isotope fractionationReferences edit Miller Dana L Mora Claudia I Grissino Mayer Henri D Mock Cary J Uhle Maria E Sharp Zachary July 31 September 19 2006 Tree ring isotope records of tropical cyclone activity Proceedings of the National Academy of Sciences 2006 National Acad Sciences Vol 103 National Acad Sciences pp 14294 14297 doi 10 1073 pnas 0606549103 PMC 1570183 Retrieved 2009 11 11 a b Tsang Man Yin Yao Weiqi Tse Kevin 2020 Kim Il Nam ed Oxidized silver cups can skew oxygen isotope results of small samples Experimental Results 1 e12 doi 10 1017 exp 2020 15 ISSN 2516 712X Paleoclimatology The Oxygen Balance Nasa Earth Observatory 2005 05 06 Retrieved 2012 02 27 Zeebe Richard E 1999 An explanation of the effect of seawater carbonate concentration on foraminiferal oxygen isotopes Geochimica et Cosmochimica Acta 63 13 14 2001 2007 Bibcode 1999GeCoA 63 2001Z doi 10 1016 S0016 7037 99 00091 5 Timothy W Lyons Christopher T Reinhard Noah J Planavsky 2014 Atmospheric oxygenation three billion years ago Nature 506 7488 307 315 Bibcode 2014Natur 506 307L doi 10 1038 nature13068 PMID 24553238 S2CID 4443958 The ups and downs of early atmospheric oxygen ScienceDaily Press release February 19 2014 Encyclopaedia Britannica under Climate and Weather Pleistocene Climatic Change Craig Harmon 1961 Isotopic variations in meteoric waters Science 133 3465 1702 1703 Bibcode 1961Sci 133 1702C doi 10 1126 science 133 3465 1702 PMID 17814749 S2CID 34373069 Epstein S Mayeda T 1953 Variation of O18 content of waters from natural sources Geochimica et Cosmochimica Acta 4 5 213 224 Bibcode 1953GeCoA 4 213E doi 10 1016 0016 7037 53 90051 9 Veizer Jan Godderis Yves Francois Louis M 2000 Evidence for decoupling of atmospheric CO2 and global climate during the Phanerozoic eon PDF Nature 408 6813 698 701 Bibcode 2000Natur 408 698V doi 10 1038 35047044 PMID 11130067 S2CID 4372892 Archived from the original PDF on 2013 10 06 Retrieved 2014 10 23 External links editNASA Earth Observatory The Oxygen Balance Scripps O2 Global Oxygen Measurements Retrieved from https en wikipedia org w index php title Oxygen isotope ratio cycle amp oldid 1165490731, wikipedia, wiki, book, books, library,

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