Dissolved Organic Matter distribution reactivity and composition Typical

Dissolved Organic Matter distribution, reactivity, and composition

Typical 1 D 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 2013 CMORE Agouron Repeta Lecture 1 Data from Peltzer and Hayward (1996) DSR 2

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

Atlantic A 16 Pacific P P 16 From Dennis Hansell CLIVAR data set 2013 CMORE Agouron Repeta Lecture 1 4

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

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

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

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

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

Mc. Nichol and Aluwihare 2007 2013 CMORE Agouron Repeta Lecture 1 10

DOC cycling via DO 14 C UV photooxidation Depth 14 C(‰) Age 1880 m -351 ‰ -3470+330 ybp 1920 m -341 ‰ -3350+300 ybp Williams, Oeschger, and Kinney; Nature v 224 (1969) 2013 CMORE Agouron Repeta Lecture 1 11

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

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

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

Radiocarbon in the Atlantic and Pacific Oceans DIC 14 C 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 sinking POC Sargasso suspended POC 15

Radiocarbon in the Atlantic and Pacific Oceans DIC 14 C 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) 14 C of DIC and DOC is about the same in the deep Atlantic and Pacific suspended POC Pacific sinking POC Sargasso suspended POC 16

Radiocarbon in the Atlantic and Pacific Oceans DIC 14 C 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) 14 C 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 Eithere is a source of “old” DOC, or DOC persists for several ocean mixing cycles. 17

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

Cycling of reactive and semi-labile DOC by phytoplankton and bacteria CO 2 Heterotrophic bacteria Autotrophic microbes DOC”reactive” O 2 DOC”semi-labile” Bacterial growth and respiration is thought to be fueled by very reactive DOC that has a residence time in seawater of hour to days. DOC”semi-labile” 2013 CMORE Agouron Repeta Lecture 1 19

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 20

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

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

Could there be a transfer of carbon from the surface water into the deep ocean ? [DOC] Depth [DOC] 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. UV photooxidation Smaller amount of very old DOC, and a larger amount of younger DOC 2013 CMORE Agouron Repeta Lecture 1 23

2013 CMORE Agouron Repeta Lecture 1 24