Hostname: page-component-8448b6f56d-tj2md Total loading time: 0 Render date: 2024-04-24T16:01:38.468Z Has data issue: false hasContentIssue false
  • English
  • Français

The Mysterious 14C Decline

Published online by Cambridge University Press:  18 July 2016

Wallace Broecker
Wallace Broecker*
Affiliation:
Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, PO Box 1000, Palisades, New York 10964-8000, USA. Email: broecker@ldeo.columbia.edu
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Fundamental to the field of radiocarbon dating is not only the establishment of the temporal record of the calendar age-radiocarbon age offsets but also the development of an understanding of their cause. Although part of the decline in the magnitude of this offset over the past 40,000 can be explained by a drop in 14C production rate associated with a progressive increase in the strength of the Earth's magnetic shielding, it is clear that changes in the distribution of 14C among the Earth's active carbon reservoirs are also required. In particular, the steep 15% decline in the 14C to C ratio in atmospheric CO2 and surface ocean ΣCO2, which occurred in a 3 kyr-duration interval marking the onset of the last deglaciation, appears to require that a very large amount (at least 5000 gigatons) of 14C-deficient carbon was transferred to or within the ocean during this time interval. As no chemical or stable isotope anomaly associated with this injection appears in either the marine sediment or polar ice records, this injection must involve a transfer within the ocean (i.e. a mixing of 2 ocean reservoirs, one depleted in 14C and the other enriched in 14C). Although evidence for the existence of a salt-stabilized glacial-age abyssal ocean reservoir exists, a search based on benthic-planktic age differences and 13C measurements appears to place a limit on its size well below that required to account for the steep 14C decline.

Type
Applications, Developments, and Historical Perspectives
Information
Radiocarbon , Volume 51 , Issue 1 , 2009 , pp. 109 - 119
Copyright
Copyright © 2009 by the Arizona Board of Regents on behalf of the University of Arizona 

References

REFERENCES

Adkins, JF, McIntyre, K, Schrag, DP. 2002. The salinity, temperature, and δ18O of the glacial deep ocean. Science 298(5599):1769–73.CrossRefGoogle ScholarPubMed
Bard, E, Hamelin, B, Fairbanks, RG, Zindler, A. 1990. Calibration of 14C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals. Nature 345(6274):405–10.Google Scholar
Beck, JW, Richards, DA, Edwards, RL, Silverman, BW, Smart, PL, Donahue, DJ, Hererra-Osterheld, S, Burr, GS, Calsoyas, L, Jull, AJT, Biddulph, D. 2001. Extremely large variations of atmospheric 14C concentration during the last glacial period. Science 292(5526):2453–8.Google Scholar
Broecker, WS. 1991. The great ocean conveyor. Oceanography 4(2):79–89.Google Scholar
Broecker, WS. 2003. Does the trigger for abrupt climate change reside in the ocean or in the atmosphere? Science 300(5625):1519–22.CrossRefGoogle ScholarPubMed
Broecker, W, Barker, S. 2007. A 190‰ drop in atmosphere's Δ14C during the “Mystery Interval” (17.5 to 14.5 kyr). Earth and Planetary Science Letters 256(1–2):90–9.Google Scholar
Broecker, WS, Kaufman, A. 1965. Radiocarbon chronology of Lake Lahontan and Lake Bonneville II, Great Basin. Bulletin of the Geological Society of America 76(5):537–66.CrossRefGoogle Scholar
Broecker, WS, Peng, T-H. 1982. Tracers in the Sea. Palisades, New York, USA: Eldigio Press. 690 p.Google Scholar
Broecker, WS, Peng, T-H, Trumbore, S, Bonani, G, Wolfli, W. 1990. The distribution of radiocarbon in the glacial ocean. Global Biogeochemical Cycles 4(1):103–17.Google Scholar
Broecker, W, Barker, S, Clark, E, Hajdas, I, Bonani, G, Stott, L. 2004. Ventilation of the glacial deep Pacific Ocean. Science 306(5699):1169–72.Google ScholarPubMed
Broecker, W, Clark, E, Barker, S, Hajdas, I, Bonani, G, Moreno, E. 2007. Radiocarbon age of late glacial deep water from the equatorial Pacific. Paleoceanography 22, PA2206, doi:10.1029/2006PA001359.CrossRefGoogle Scholar
Broecker, W, Clark, E, Barker, S. 2008. Near constancy of the Pacific Ocean surface to mid-depth radiocarbon-age difference over the last 20 kyr. Earth and Planetary Science Letters 274(3–4):322–6.Google Scholar
Damon, PE, Lerman, JC, Long, A. 1978. Temporal fluctuations of atmospheric 14C: causal factors and implications. Annual Review of Earth and Planetary Science 6:457–94.Google Scholar
Denton, GH, Broecker, WS, Alley, RB. 2006. The mystery interval 17.5 to 14.5 kyrs ago. PAGES News 14(2):14–6.Google Scholar
de Vries, HL. 1958. Variation in concentration of radiocarbon with time and location on Earth. Proceedings Koninlijke Nederlandse Akademie Wetenschappen B 61:94–102.Google Scholar
Edwards, RL, Chen, JH, Wasserburg, GJ. 1987. 238U-234U-230Th-232Th systematics and the precise measurement of time over the past 500,000 yrs. Earth and Planetary Science Letters 81(2–3):175–92.Google Scholar
Fairbanks, RG, Mortlock, RA, Chiu, T-C, Cao, L, Kaplan, A, Guilderson, TP, Fairbanks, TW, Bloom, AL, Grootes, PM, Nadeau, M-J. 2005. Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/234U/238U and 14C dates on pristine corals. Quaternary Science Reviews 24(16–17):1781–96.Google Scholar
Galbraith, ED, Jaccard, SL, Pedersen, TF, Sigman, DM, Haug, GH, Cook, M, Southon, JR, Francois, R. 2007. Carbon dioxide release from the North Pacific abyss during the last deglaciation. Nature 449(7164):890–3.Google Scholar
Hughen, KA, Overpeck, JT, Lehman, SJ, Kashgarian, M, Southon, J, Peterson, LC, Alley, R, Sigman, DM. 1998. Deglacial changes in ocean circulation from an extended radiocarbon calibration. Nature 391(6662):65–8.Google Scholar
Hughen, KA, Southon, JR, Lehman, SJ, Overpeck, JT. 2000. Synchronous radiocarbon and climate shifts during the last deglaciation. Science 290(5498):1951–4.Google Scholar
Hughen, K, Lehman, S, Southon, J, Overpeck, J, Marchal, O, Herring, C, Turnbull, J. 2004. 14C activity and global carbon cycle changes over the past 50,000 years. Science 303(5655):202–7.Google Scholar
Keigwin, LD. 1998. Glacial-age hydrography of the far northwest Pacific Ocean. Paleoceanography 13(4):323–39.Google Scholar
Kromer, B, Becker, B. 1993. German oak and pine 14C calibration, 7200–9439 BC. Radiocarbon 35(1):125–35.Google Scholar
Marchitto, TM, Lehman, SJ, Ortiz, JD, Flückiger, J, van Geen, A. 2007. Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise. Science 316(5830):1456–9.Google Scholar
Muscheler, R, Beer, J, Wagner, G, Laj, C, Kissel, C, Raisbeck, GM, Yiou, F, Kubik, PW. 2004. Changes in the carbon cycle during the last deglaciation as indicated by the comparison of 10Be and 14C records. Earth and Planetary Science Letters 219(3–4):325–40.Google Scholar
Ohkushi, K, Uchida, M, Ahagon, N, Mishima, T, Kanematsu, T. 2004. Glacial intermediate water ventilation in the northwestern Pacific based on AMS radiocarbon dating. Nuclear Instruments and Methods in Physics Research B 223–224:460–5.Google Scholar
Peng, T-H, Broecker, WS. 1984. The impacts of bioturbation on the age difference between benthic and planktonic foraminifera in deep sea sediments. Nuclear Instruments and Methods in Physics Research B 5(2):346–52.Google Scholar
Stott, L, Timmermann, A, Thunell, R. 2007. Southern Hemisphere and deep-sea warming led deglacial atmospheric CO2 rise and tropical warming. Science 318(5849):435–8.CrossRefGoogle ScholarPubMed
Stuiver, M. 1982. A high-precision calibration of the AD radiocarbon time scale. Radiocarbon 24(1):1–26.Google Scholar
Suess, HE. 1965. Secular variations in the cosmic-ray-produced carbon 14 in the atmosphere and their interpretations. Journal of Geophysical Research 70(23):5937–52.Google Scholar