GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze

1. GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) ChristophHeinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in Global Carbon Cycle Modelling Allegaten 70, N-5007 Bergen, Norway Phone: +47 55 58 98 44 Fax: +47 55 58 98 83 Mobile phone: +47 975 57 119 Email: christoph.heinze@gfi.uib.no DEAR STUDENT AND COLLEAGUE: ”This presentation is for teaching/learning purposes only. Do not useany material ofthispresentation for any purpose outsidecourse GEOF236, ”Chemical Oceanography”, autumn 2012, Universityof Bergen. Thankyou for yourattention.”

2. Sarmiento&Gruber 2006 Chapter 5: Organic matter export and remineralisation, part 2

3. Primary production and export production estimated from satellite and sediment trap measurements: Satellite derived estimate (following Carr, 2002) Source: Henson, S., et al., 2012, Global patterns in efficiency of particulate organic carbon export and transfer to the deep ocean, Global Biogeochemical Cycles, 26, GB1028

4. Top sediment distribution of organic carbon Source: Jahnke, R., The global ocean flux of particulate organic carbon: Areal distribution and magnitude, Global Biogeochemical Cycles, 10(1), 71-88.

5. Primary and export production reflected in sediment coverage? The Open University/Pergamon: Ocean Chemistry and Deep-Sea Sediments, 1989

6. Example for a sediment trap for measuring particle fluxes in the water column: After: Asper, SCOOPE 57(Ittekkot et al.), 1996)

7. Simplified view on organic matter flux from the euphotic zone to deeper layers: Source: Sarmiento&Gruber 2006

8. The longer the time after the last contact with the atmosphere – the more dissolved nutrients are found in water as a result of particle rain and organic matter degradation – very roughly “oldest water = highest nutrient concentration”: Source: Sarmiento&Gruber 2006

9. Redfield ratio – why is the correlation between oxygen and phosphate worse than that between nitrate and phosphate? Source: Sarmiento&Gruber 2006

10. N cycling and the denitrification reaction: Denitrification: Source: Sarmiento&Gruber 2006

11. Concentrations of biogeochemical tracers can be structure into observed, preformed, and remineralised ones BLACK BOARD Source: Sarmiento&Gruber 2006

12. Apparent oxygen utilisation AOU and oxygen utilisation rate OUR BLACK BOARD

13. The “older” the water gets the lower is the dissolved oxygen concentration – deep water averages below 2000m depth: Δ(Δ14C)decayed= (Δ14C)observed -(Δ14C)preformed Δ[O2]remin= Δ[O2]observed -Δ[O2]preformed Δ14C= δ14C – 2 ∙(δ13C + 25)∙(1 + {δ14C/1000}), the δ-values are deviations of the isotopic ratios from standards, the 2nd term on the right side is to make the radiocarbon in seawater comparable to those in terrestrial wood due to fractionation effects Source: Sarmiento&Gruber 2006

14. Apparent oxygen utilisation AOU on isopycnic surfaces in the North Atlantic: Source: Sarmiento&Gruber 2006

15. OUR – oxygen utilisation rates - estimates in the upper kilometre of the water column using different methods: Large uncertainties a.o. because of the degree of mixing of water masses which severely can influence the apparent age. Source: Sarmiento&Gruber 2006

16. What happens to the nutrients PO43- and NO3- and other compounds due to the remineralisation process (i.e. due to the degradation of organic matter)? We can look at the observed values and use stoichiometry considerations (“Redfield ratios”) to reconstruct the preformed and remineralised fractions. Consider n “end-members” which contribute fractions fi, i=1,…,n to a certain water parcel: Source: Sarmiento&Gruber 2006

17. Element ratios of remineralised fractions (or originally organic matter) in the water column as a function of depth (from end-member model fit to obs.): We show here directly the diagrams of Anderson and Sarmiento, 1994, Global Biogeochemical Cycles, 8(1), p. 65-80, and not Fig. 5.3.1 and 5.3.2 from the Sarmiento&Gruber textbook. 1000-3000m minimum due to denitrification? (also in sediments)

18. Element ratios of remineralised fractions (or originally organic matter) in the water column as a function of depth (from end-member model fit to obs.): Summary for deep Pacific following Anderson & Sarmiento (1994)

19. Element ratios of remineralised fractions (or originally organic matter) in the water column as a function of depth (from end-member model fit to obs.) – Arabian Sea: . Hupe, A., and J. Karstensen, 2000, Redfield stoichiometry in Arabian Sea subsurface waters, Global Biogeochemical Cycles, 14(1), 357-372. Possibly faster mobilisation of nutrients than carbon in upper waters

20. The phosphate (PO43-) cycle is relatively simple – one can split into preformed and remineralised fractions through stoichiometry considerations: Δ[PO43-]remin = -rP:O2 ∙ AOU; [PO43-]preformed = [PO43-]observed - Δ[PO43-]remin Source: Sarmiento&Gruber 2006

21. N*: The nitrogen cycle is more complicated. In order to take into account denitrification (NO3- degradation under oxygen poor conditions) and nitrification (N2 fixation at the surface) one can define and plot the useful tracer N*. BLACK BOARD

22. Global N* section: Vertical N* profiles: Source: Sarmiento&Gruber 2006

23. Denitrification and N2 fixation in the N/P Redfield diagram: Source: Sarmiento&Gruber 2006