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Radiocarbon Course Students:

Radiocarbon Course Students: These slides are provided for your reference. If you wish to use any of these slides, please make sure to contact the appropriate lecturer first for permission and attribution. Thank you. UCI AMS Short Course 2011 14 C in the Oceans. Outline

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Radiocarbon Course Students:

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  1. Radiocarbon Course Students: These slides are provided for your reference. If you wish to use any of these slides, please make sure to contact the appropriate lecturer first for permission and attribution. Thank you.

  2. UCI AMS Short Course 2011 14C in the Oceans Outline • Major carbon reservoirs • Why is the surface ocean several hundred years old? • Controls on oceanic 14C • Corals as diaries of ocean mixing and past climate • Mixing time of the deep ocean conveyor • 14C in particles, old dissolved organic carbon and sediment • Compound specific radiocarbon analyses (CSRA)

  3. Definitions • DOC - dissolved organic carbon (<1µm) • POC - particulate organic carbon (>1µm) • Sinking POC - OC caught in a trap • Suspended POC - OC filtered by a pump • DIC - dissolved inorganic carbon (CO2, HCO3-, CO3=)

  4. Masiello, 1999 Rivers Surface DIC: 1020 Gt t = 1-10 y Ocean IC Ocean OC

  5. Why does the ocean contain so much DIC? • CO2 hydrates to H2CO3 CO2(gas) + H2O <---> H2CO3 H2CO3(0.5%) <---> H+ + HCO3- (89%) HCO3- <---> H+ + CO3=(11%)

  6. CO2 ~20 mol/m2/y [CO2(aq)HCO3-CO3=]= 200 mol/m2 Exchange of surface ocean DIC and atmospheric CO2 Air Residence = 200mol/m2 = 10 y Time20mol/m2/y Surface Ocean But 14C age of surface ocean >>10 y … WHY?

  7. FM ∆14C 14C age CO2 20 mol/m2/y [DIC] =200 mol/m2 ‘Reservoir Age’of Non-Polar Surface DIC • Why is the surface ocean so “old” (330-600 14C y)? 1. Mixing of deeper, older waters into the surface [2. Slow turnover time wrt atmospheric exchange of CO2 Previous slide] • Mixing dominates, so 14C is a water mass tracer, not a tracer of sea-air gas exchange 1.0 0‰ 0 14C y Air .928-.96 -72 to -40‰ 600- 330 14C y Surface Ocean >20 mol/m2/y .92-.95 -80 to -50‰ 700- 420 14C y Subsurface Ocean

  8. Controls on 14C in the ocean are…Winds…

  9. and the Coriolis Force - Ekman Transport produces Ekman spiral Force In mid-gyre: Surface ∆ = -40‰ Subsurface ∆ = -50‰ Motion …In Northern Hemisphere, motion of water is to the right of force

  10. -40 to -45‰ -55 to -72‰ -40 to -50‰ -100 to -160‰ Surface currents and surface ∆14C = Mid-ocean gyre

  11. Tales of past surface circulation + climate from corals We assume: ∆14Ccoral = ∆14CDIC in seawater 18Ocoral = f (SST and 18Owater)

  12. Sectioning of Coral Cores Mapped Slab core slab X-ray Sampled using saw or Dremel tool AMS analysis

  13. D (known-age corrected samples ) Corrected for decay of 14C in the sample from the year of growth (x) to 1950 D expresses the radiocarbon signature relative to “Modern” had the sample been measured in 1950. This is useful for studies attempting to show how the radiocarbon signature of air (tree rings) and water (corals) changes with time. It is the basis for creating the calibration curves used to calculate calendar age from radiocarbon age.

  14. Bomb 14C maximum in surface ocean occurs 10 y after that in the air ∆14C ‰ Atmospheric CO2 Mid-ocean gyre surface water DIC (coral)

  15. El Niño/Southern Oscillation Normal - •strong SE trade winds, upwelling •cool in east, warm in west •high rain in west El Niño -•weak SE trade winds or reversal •warm water moves from west to east •high rain in mid- and east Pacific -50‰ -72‰ = ∆14C -65‰ -55‰

  16. Galapagos coral 14C • El Niño ∆14C -55 to -45‰ • Normal periods -70 to -60‰ • Sustained low 14C (early 1600s, early 1800s) coincident with high volcanic aerosol loading in the atmosphere GRL, 2007

  17. Major water Masses in the Atlantic -- AAIW, AABW and NADW ∆14C -80‰ ∆14C -160‰

  18. Collection of DIC and DOC samples using Go-flo bottles

  19. DOC, DIC and suspended POC collection Small Yentsch pumps filter seawater through quartz fiber filters to collect suspended POC Niskin or go-flo bottles used to collect clean seawater, filtered with millipore or GFF

  20. Deep Ocean Conveyor Belt NCP SS 2-4 km deep tongue of NADW

  21. DIC 14C ∆14C Pre-bomb Depth (m) NADW aged 1500 y SS->NCP

  22. Deep DIC ∆14C and 14C ages 670 14C y -80‰ 2200 14C y -240‰ ~1500 14C y difference = transit time of the conveyor

  23. Dissolved Organic C (DOC) in the Oceans • Largest marine OC reservoir, 685 GtC • Mostly marine-derived. How much from land? • Chemically heterogeneous • Bulk ages are very old Hedges, J.I. (2002) DOC (like chicken broth)

  24. UV Hg-arc lamp, Quartz reactor and… The Can

  25. 14 D DOC C (‰) -800 -600 -400 -200 0 Station M In seawater from Stn M - off Pt. Conception, CA Beaupré et al 2007 m [DOC] ( M) 0 20 40 60 80 0 1000 2000 Depth (m) 3000 4000 5000 ~ 7000 14C y old

  26. Pulse 45, 0.2mm filtered 2000m time series Beaupré et al 2007

  27. > 0.001 mm (like chicken pieces in broth) - Includes: organic: e.g., fecal pellets, forams, radiolarians... organic/inorganic: e.g., marine snow minerals: e.g., clay, silt, sand, beer cans .05-5µM C in seawater caught by: sediment traps, or pumps Particulate Organic C (POC)

  28. Suspended POC ∆14C - Sargasso vs N Pacific ∆14C Depth (m) • There shouldn’t be a depth gradient, if all POC originates from surface waters. • Hwang et al (2011) observed a linear correlation between ∆14C and [Al], indicating old resuspended sediment is in POC. Sargasso PO14C is lower

  29. Organic Fractions Radiocarbon Analyses (OFRA) of bulk POC in the NE Pacific (Hwang et al 2003, 2004, 2005) • ∆14C of carbohydrates and proteins are higher than lipids and acid-insoluble OC • Lipids are older than carbohydrates and proteins • Lipids may be precursors of acid-insoluble OC POCsink

  30. Constituents of SedimentsDatable by 14C are:foramscoccolithsfecal pelletsplantsfishmarine snowblack carbonAlysha Coppola

  31. Compound specific radiocarbon analyses (CSRA) Lipids studied by Pearson et al (2001) in sediments and Ingalls et al (2006) in Archaea N-alkane C15:0 fatty acid C30 -alkan-15-one-1-ol Archaeal C40 isoprenoid GDG Tetraethers (archaeal membrane lipids) cholesterol hopanol

  32. CSRA if lipids in Santa Monica Basin sediments (Pearson et al 2001)Postbomb sediment (solid symbols), prebomb sediment (open symbols).

  33. Summary • 14C is a water mass tracer, rather than a tracer of gas exchange • 14C is a tracer of past climate • CSRA is possible, but blanks are very important • 14C is a tracer of land-derived BC in the oceans – Alysha Coppola

  34. Masiello, 1999 Rivers Oceanic DOC: 685 Gt τ=~6000 y Oceanic DIC: 38,000 Gt τ=~2000 y

  35. Masiello, 1999 Rivers Oceanic DOC: 685 Gt τ=~6000 y Why is DOC older? Oceanic DIC: 38,000 Gt τ=~2000 y

  36. What is the Influence of Black Carbon in Marine Dissolved Organic Carbon Pool? Alysha Inez Coppola Druffel Group

  37. Distribution of Radiocarbon in the Environment McNichol and Aluwihare, 2007

  38. Dissolved Organic Carbon is operationally defined • OC passing through a 1 μm filter • 20-25% of DOC is high molecular weight (HMW) • 75-80% is low molecular weight (LMW) Molecular wt 106 105 104 103 102 101 Modified from Hedges, 2002

  39. Dissolved Organic Carbon is operationally defined • OC passing through a 1 μm filter • 20-25% of DOC is high molecular weight (HMW) • 75-80% is low molecular weight (LMW) Molecular wt 106 105 104103 102 101 HMW LMW? Modified from Hedges, 2002

  40. DOC is older than DIC • DOC ~2,400 14C yrs older than DIC • DOC 4,000-6,500 14C yrs • DIC 700-2,400 14C yrs • N. Atlantic • N. Pacific • Southern Ocean (Druffel and Bauer, 2000) (Druffel and Bauer, 2000)

  41. Entire vertical distribution of DO14C can be explained by a mixture of 2 components • 1. labile: 70 μM, Δ14C=-250‰ • 2. Refractory: 35 μM, Δ14C=-550‰ Mortazavi and Chanton, 2004

  42. Entire vertical distribution of DO14C can be explained by a mixture of 2 components DOCsurface=DOCdeep+DOCxs Δ14CsurfaceDOCsurface=Δ14CdeepDOCdeep+Δ14CxsDOCxs -210 ‰ -214‰ -153 ‰ -155 ‰ -398 ‰ -372‰

  43. Use Keeling plots to calculate Δ14Cmodern w/o assuming a value for Δ14Crefractory DOCz=DOCrefractory+DOCmodern Δ14CzDOCz=Δ14CrefDOCref+Δ14CmodDOCmod Δ14Cz=Δ14Cmod+ 1 [DOCrefΔ14Cref-DOCrefΔ14Cmod] Δ14Cz 1/[DOC]z, μM-1 DOCz

  44. What is in the refractory component of DOC? • Black carbon (BC) may contribute to the old age of DOC Black Carbon?

  45. What is in the refractory component of DOC? • Black carbon (BC) may contribute to the old age of DOC Black Carbon? Biomass fossil fuel burning combustion

  46. What is in the refractory component of DOC? • Black carbon (BC) may contribute to the old age of DOC • Evidence: • 1. There is a missing BC sink in the BC cycle • 2. Offset in 14C ages between BC and non-BC in sediments • 3. BC was found in HMW DOC by Ziolkowski and Druffel, 2009 Black Carbon?

  47. 1. Missing sink in BC budget Modified from Kuhlbusch, 1998; Suman et al., 1997; Penner et al., 1993; Masiello 2000

  48. 2. Ziolkowski and Druffel (2010) found BC in HMW DOC • Found 0.5-3.5% of HMW DOC is BC • Oldest is in the ocean • 2 Riverine BC • 2 surface ocean BC • 1 Deep oceanic BC

  49. 2. Ziolkowski and Druffel (2010) found BC in HMW DOC • Found 0.5-3.5% of HMW DOC is BC • Oldest is in ocean • 2 Riverine BC • 2 surface ocean BC • 1 Deep oceanic BC HMW LMW

  50. 3. Age Offset between BC and non-BC SOC • Masiello and Druffel (1998) found age offset • τ= 2,400 ±120 14C y NE Pacific • We also see offset using a different method • τ= 5,900±1000 14C y NE Pacific

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