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Dissolved Organic Matter distribution, reactivity, and composition

Dissolved Organic Matter distribution, reactivity, and composition. Typical 1D profile of dissolved organic carbon in the ocean. TOC (µM). Often measured as TOC Surface values typically 60-80 µM Deep water values @ 40 µM (implies some unknown feedback/ control of DOC values)

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Dissolved Organic Matter distribution, reactivity, and composition

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  1. Dissolved Organic Matter distribution, reactivity, and composition

  2. Typical 1D profile of dissolved organic carbon in the ocean TOC (µM) Often measured as TOC Surface values typically 60-80 µM Deep water values @ 40 µM (implies some unknown feedback/ control of DOC values) Global inventory about 660 GT C Data from Peltzer and Hayward (1996) DSR 2013 CMORE Agouron Repeta Lecture 1

  3. Global Dissolved Organic carbon (< 30 m) Hansell et al., GBC 2012 2013 CMORE Agouron Repeta Lecture 1

  4. Atlantic A16 Pacific P P16 2013 CMORE Agouron Repeta Lecture 1 From Dennis Hansell CLIVAR data set

  5. http://www.global-greenhouse-warming.com/images/thermohaline.jpghttp://www.global-greenhouse-warming.com/images/thermohaline.jpg 2013 CMORE Agouron Repeta Lecture 1

  6. Global circulation and the distribution of DOC Hansell et al. Oceanography 2009 2013 CMORE Agouron Repeta Lecture 1

  7. How do we measure carbon fluxes in DOC ? 2013 CMORE Agouron Repeta Lecture 1

  8. National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) C-14 tracer measurements use >106x more C-14 than natural abundance!!!!! 2013 CMORE Agouron Repeta Lecture 1

  9. History of radiocarbon in the atmosphere and ocean McNichol and Aluwihare, Chem Rev. 2007 2013 CMORE Agouron Repeta Lecture 1

  10. 2013 CMORE Agouron Repeta Lecture 1 McNichol and Aluwihare 2007

  11. DOC cycling via DO14C UV photooxidation Depth 14C(‰) Age 1880m -351 ‰ -3470+330 ybp 1920m -341 ‰ -3350+300 ybp Williams, Oeschger, and Kinney; Nature v224 (1969) 2013 CMORE Agouron Repeta Lecture 1

  12. Radiocarbon in the Atlantic and Pacific Oceans Peter M. Williams and Ellen Druffel; Nature 1987, JGR 1992

  13. Radiocarbon in the Atlantic and Pacific Oceans Pacific suspended POC Pacific sinking POC Sargasso suspended POC

  14. Radiocarbon in the Atlantic and Pacific Oceans DIC 14C in surface waters of the Atlantic and Pacific have similar isotopic values. Pacific suspended POC Pacific sinking POC Sargasso suspended POC

  15. Radiocarbon in the Atlantic and Pacific Oceans DIC 14C in surface waters of the Atlantic and Pacific have similar isotopic values. DOC is always older than DIC (by 2-3 kyrs in surface water) DIC POC DOC Pacific suspended POC Pacific suspended POC Pacific sinking POC Pacific sinking POC Sargasso suspended POC Sargasso suspended POC

  16. Radiocarbon in the Atlantic and Pacific Oceans DIC 14C in surface waters of the Atlantic and Pacific have similar isotopic values. DOC is always older than DIC (by 2-3 kyrs in surface water) 14C of DIC and DOC is about the same in the deep Atlantic and Pacific Pacific suspended POC Pacific suspended POC Pacific sinking POC Pacific sinking POC Sargasso suspended POC Sargasso suspended POC

  17. Radiocarbon in the Atlantic and Pacific Oceans DIC 14C in surface waters of the Atlantic and Pacific have similar isotopic values. DOC is always older than DIC (by 2-3 kyrs in surface water) 14C of DIC and DOC is about the same in the deep Atlantic and Pacific Deep ocean values of DOC are equal to a radiocarbon age of 4-6 kyrs Either there is a source of “old” DOC, or DOC persists for several ocean mixing cycles.

  18. Radiocarbon based models of DOC cycling in the water column Old (low radiocarbon), non-reactive DOC New, semi-reactive DOC Atlantic surface water 14Ccalc = -120 ‰ 14Cobs = -127 ‰ Pacific surface water 14Ccalc = -147 ‰ 14Cobs = -148 ‰ Williams and Druffel, 1987; Beaupre and Druffel 2009 2013 CMORE Agouron Repeta Lecture 1

  19. DOC”semi-labile” DOC”reactive” O2 DOC”semi-labile” Cycling of reactive and semi-labile DOC by phytoplankton and bacteria CO2 Heterotrophic bacteria Autotrophic microbes Bacterial growth and respiration is thought to be fueled by very reactive DOC that has a residence time in seawater of hour to days. 2013 CMORE Agouron Repeta Lecture 1

  20. Under this perspective, DOM is produced and rendered recalcitrant by marine microbes. Combined with the two component model of radiocarbon and deep sea DOC, it suggests no or at best very slow removal of DOM in the deep sea 2013 CMORE Agouron Repeta Lecture 1

  21. Very rapid degradation of DOC in the Mediterranean Sea. If DOC is refractory, why does this happen? LIW Depth (m) 40 mM 34 mM C. Sanitelli et al. 2013 2013 CMORE Agouron Repeta Lecture 1

  22. Southern Ocean DOC-14 data suggests the two component model cannot be correct. 2013 CMORE Agouron Repeta Lecture 1

  23. Could there be a transfer of carbon from the surface water into the deep ocean ? UV photooxidation The two component model only requires a conservation of mass and isotopic abundance, but does not stipulate what the isotopic/mass distribution of DOC is within the old (deep) fraction of DOC. A number of mass/isotope mixes can constitute the old fraction of DOC. [DOC] [DOC] Depth Smaller amount of very old DOC, and a larger amount of younger DOC 2013 CMORE Agouron Repeta Lecture 1

  24. 2013 CMORE Agouron Repeta Lecture 1

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