1. OCN520 Fall 2009 Mid-Term #2 Review Since Mid-Term #1 Ocean Carbonate Distributions Ocean Acidification Stable Isotopes Radioactive Isotopes Nutrients and Production POC Export and Respiration O2: Ventilation versus Respiration

2. Sarmiento and Gruber (2002) Sinks for Anthropogenic Carbon Physics Today August 2002 30-36

3. Ocean Distributions – versus depth, versus ocean Atlantic Pacific Points: 1. Uniform surface concentrations 2. Surface depletion - Deep enrichment 3. DIC < Alk  DIC >  Alk See Key et al (2004) GBC Q?

4. The main features are: 1. uniform surface values 2. increase with depth 3. Deep ocean values increase from the Atlantic to the Pacific 4. DIC < Alk  DIC >  Alk 5. Profile of pH is similar in shape to O 2. 6. Profile of P CO2 (not shown) mirrors O 2. Ocean Distributions of, DIC, Alk, O 2 and PO 4 versus Depth and Ocean

5. Paleo Nutrient Distributions Boyle and Keigwin (1982) Science Data in benthic forams – North Atlantic

6. Controls on Ocean Distributions A) Photosynthesis/Respiration Organic matter (approximated as CH 2 O for this example) is produced and consumed as follows: CH 2 O + O 2  CO 2 + H 2 O Then: CO 2 + H 2 O  H 2 CO 3 * H 2 CO 3 *  H + + HCO 3 - HCO 3 -  H + + CO 3 2- As CO 2 is produced during respiration we should observe: pH  DIC  Alk  P CO2  The trends will be the opposite for photosynthesis. B) CaCO 3 dissolution/precipitation CaCO 3 (s)  Ca 2+ + CO 3 2- Also written as: CaCO 3 (s) + CO 2 + H 2 O  Ca 2+ + 2 HCO 3 - As CaCO 3 (s) dissolves, CO 3 2- is added to solution. We should observe: pH  DIC  Alk  P CO2 

7. Emerson and Hedges Color Plate  DIC/  Alk ≈ 1.5/1 Work Backwards  Alk /  DIC ≈ 0.66 = 2/3 = 2 mol Org C / 1 mol CaCO 3

8.  18 O of planktonic and benthic foraminifera from piston core V28-238 (160ºE 1ºN) Planktonic and Benthic differ due to differences in water temperature where they grow. Planktonic forams measure sea surface T Benthic forams measure benthic T Example: Estimation of temperature in ancient ocean environments CaCO 3 (s) + H 2 18 O  CaC 18 OO 2 + H 2 O The exchange of 18 O between CaCO 3 and H 2 O The distribution is Temperature dependent Assumptions: 1. Organism ppted CaCO 3 in isotopic equilibrium with dissolved CO 3 2- 2. The δ 18 O of the original water is known 3. The δ 18 O of the shell has remained unchanged last glacialHolocene last interglacial

9. δ 13 C in different reservoirs E & H Fig. 5.6

10. Distillation of meteoric water – large kinetic fractionation occurs between ocean and vapor. Then rain forming in clouds is in equilibrium with vapor and is heavier that the vapor. Vapor becomes progressively lighter.  D and  18 O get lower with distance from source. Water evaporation is a kinetic effect. Vapor is lighter than liquid. At 20ºC the difference is 9‰ (see Raleigh plot). The BP of H 2 18 O is higher than for H 2 16 O Air masses transported to higher latitudes where it is cooler. water lost due to rain raindrops are rich in 18 O relative to cloud. Cloud gets lighter

12. Secular equilibrium  1/2 daughter = 0.8 hr  1/2 parent =  time (hr) Activity (log scale) daughter  1/2 parent ! Daughter grows in with half life of the daughter!

13. 222 Rn Example Profile from North Atlantic 226 Ra 222 Rn Does Secular Equilibrium Apply? t 1/2 222Rn << t 1/2 226Ra (3.8 d) (1600 yrs) YES! A 226Ra = A 222Rn Why is 222 Rn activity less than 226 Ra?

14. Coale & Bruland 1987 Particle and 234 Th Export Vertical zonation of 234 Th removal

15. Annual Mean Surface Nitrate

16. The Redfield or "RKR" Equation (A Model) The mean elemental ratio of marine organic particles is given as: P : N : C = 1 : 16 : 106 The average ocean photosynthesis (forward) and aerobic ( O 2 ) respiration (reverse) is written as: 106 CO 2 + 16 HNO 3 + H 3 PO 4 + 122 H 2 O + trace elements (e.g. Fe) light (h )  ( C 106 H 263 O 110 N 16 P ) + 138 O 2 or (CH 2 O) 106 (NH 3 ) 16 (H 3 PO 4 ) Algal Protoplasm The actual chemical species assimilated during this reaction are: HCO 3 - NO 3 - PO 4 3- NO 2 - NH 4 +

17. Food Web Cartoon PON DON Euphotic Zone (~100m) At steady state: New NO 3 = O 2 flux to atm = PON (and DON) export Follow the N! Follow the C! Follow the O 2 ! Fe plays a role!

18. Surface fingerprints: ventilation thermocline Mixed layer Atm. thermocline Mixed layer Atm. Decrease ventilation Air-sea O 2 flux ΔAOU subtropics time outcrop An increase in AOU due to decreased ventilation will cause changes in air-sea fluxes of both O 2 and CO 2 coincident with the ventilation change…

19. Surface fingerprints: export thermocline Mixed layer Atm. thermocline Mixed layer Atm. Increase export flux Export flux Air-sea O 2 flux ΔAOU outcrop time subtropics Similar AOU anomalies may be caused by increased export flux, with very different signatures of O 2 /CO 2 gas exchange.