Ocean Production and CO 2 uptake

1. Ocean Production and CO2 uptake

2. Announcements • MT results: Will be passed out in section, or wed in class for those with Monday sections. • MT “curve”: will be discussed in lecture on Wed.

3. Recall from box models: active carbon “pools” ATM CO2 Dissolved CO2 in ocean Not to scale..

4. Fig. 6.6 Recall: Current ocean is gaining Carbon.. OCEAN Reservoir size: 38000 Flux in: 90 Flux out: 88+0.2=88.2 90 - 88.2 = 1.8 Pg/yr OCEAN is gaining 1.8 Pg/yr

5. Sum of the Sources & Sinks of Anthropogenic carbon BIOTA & SOILS Flux in: 120 Flux out: 4+60+55 = 119 Net SINK: 1 Pg/yr OCEAN Flux in: 90 Flux out: 88+0.2 = 88.2 Net SINK: 1.8 Pg/yr Human SOURCES: 7.4 ± 1.0 Pg/yr Measured Atmospheric increase: 4.0 Pg/yr CALCULTED Carbon SINKS: 3.4 ± 1.0 Pg/yr Measured carbon SINKS: 2.8 Pg/yr Calculated and Measured SINKS are equal within error

6. Bottom line • A very large amount of carbon cycling through the atmosphere goes into the ocean.. But how does it do it?

7. Outline: • Chemistry. How does ocean absorb CO2, and what happens? • Biology: what does it take for plankton to grow? • 3. The two “pumps” for putting C in the deep ocean • a) Abiotic (CO2)pump- • b) Biological pump “Just Face it Brett…. No one cares about the Carbon Cycle.” (overheard)

8. 1. Chemistry

9. Focus on Atm and Ocean CO2 boxes ATM CO2 Dissolved CO2 CO2 dissolved in ocean water Is > 50 x all CO2 in atmosphere! Why? Because chemistry of ocean water can hold so much.. Not to scale..

10. Questions: 1) why can ocean hold so much CO2? 2) what does putting more CO2 into ocean do to water chemistry? `

11. Remember this stuff? Question: what is PH of water?

12. What is the Ph of “natural” water? • Natural water (rain included) is slightly acidic (Ph 5-6) • CO2 + H2O ===> H2CO3 (carbonic acid) • Aside: “Acid rain” is much stronger acid, due to SO2 emissions from coal burning- but reaction is exactly the same! SO2 + H2O ===> H2SO4
(sulfuric acid)

13. But then there is more chemistry: • 1) CO2 dissolves in sea water forming carbonic acid: CO2 + H2O => H2CO3 • 2) Carbonic acids yields bicarbonate and hydrogen ions: H2CO3 => H+ + HCO3- • 3) Bicarbonate dissociates to another Hydrogen react and Carbonate ion: HCO3- =>H+ + CO32-

14. Together this is called the“Carbonate Buffer system” • H2O + CO2 == H2CO3 == H + + HCO3- = 2 H + + CO3-2 • Note each carbon in CO2 that goes into the ocean as one thing, can turn into three separate forms • Each form has its own chemical solubility • Carbonate buffer system is central to maintaining the Ocean’s PH- AND regulating CO2 storage!

15. Overall: The Ocean is major Sink of CO2 …Because increasing levels of Atm CO2 have increased the air-sea gradients.

16. = Passive (chemical) absorption mechanism CO2 • H2O + CO2 == H2CO3 == H + + HCO3- = 2 H + + CO3-2

17. 2. Biology

18. Global Ocean Productivity

19. Recall: Life (biosphere) transforms and recycles carbon from inorganic to organic forms Inorganic matter (oxidized carbon) CO2 Organic matter (reduced carbon) CHO When ocean plankton grow- the surface ocean is taking up carbon from the atmosphere!

20. PLANKTON PHOTOSYNTHESIS: Photosynthesis light CO2 + H2O + PO4 , NO3 , (Biolimiting salts = nutrients) CH2O + O2 organic tissue + oxygen NOTE 1: Biolimiting SALTS are used UP, Oxygen is PRODUCED NOTE 2: can only happen in the SURFACE !

21. Wastes and remains.. Piece 2: PARTICLE SINKING to depth FEEDING by ANIMALS-

22. CO2 + H2O + PO4 , NO3 , (Biolimiting salts = nutrients) Piece 3: Respiration at depth ( Animals & bacteria) CH2O + O2 organic tissue + oxygen NOTE 1: Oxygen is USED UP, Biolimiting SALTS (and CO2) are PRODUCED This PROCESS is called: REMINERALIZATION - because “mineral” nutrients Salts are replaced into the deeper sea

23. Result Nutrient “Profiles” • Recall major nutrients are USED UP in surface by photosynthesis (eg: Phosphate (PO4), Nitrate (NO3), Silicate) • BUT replaced in deep ocean by remineralization of sinking particles!

24. The Plankton’s Catch-22 Where are the nutrients? Where is the Light?

25. Recall: “Stratification”Ocean is layered by density

26. “MIXED LAYER” is upper layer of water totally mixed up by the wind.. the deeper the mixed layer is, more of those deep- nutrients can reach the surface!

27. Result: MOST OF SURFACE OCEAN PRODUCTION IS “NUTRIENT LIMITED” This means, that the main thing which controls overall plankton production* is AVAILABLE NUTRIENTS in surface water (*and therefore the amount of CO2 that can be turned into plankton biomass)

28. Recall “upwelling” ?

29. Effect of Coastal UPWELLING Coastal upwelling photo This explains why upwelling areas are so intensely productive for fisheries- but also entire food chains..

30. At Most Mid-Latitude areas global upwelling patterns = production patterns

31. Higher latitudes: Highly productive during spring and summer- (when enough light)

32. Mid-Lower latitudes: More Constant,Central areas (=no upwelling) are “deserts”

33. Biological Ocean C-fixation: Summary • Plankton “draw down” atm. CO2, fix it into biomass • This is called “plankton production” • Plankton production is limited mostly by available nutrients ATM CO2  Available surface nutrients are main limit on amount of CO2 that can be removed from Atm.

34. 3. The Ocean’s two “pumps” for CO2

35. Question: Why do you need a “pump” where is the ocean pumping it to…

36. Recall those “Ocean Layers” SURFACE OCEAN THERMOCLINE DEEP OCEAN

37. Surface “mixed layer” ~ 100 meters deep (out of 4500m!!) IS ONLY PART WHERE CO2 FROM ATM CAN PENETRATE by mixing.. • ~ Same depth (~100m) is where all the ocean production can happen!

38. So: Why do you need a “pump”

39. The physical pump (“passive” CO2 uptake, no biology involved)

40. Sources/ sinks co2 Oceanic Sources and Sinks of Atmospheric Carbon Dioxide Oceanic concentration of CO2 depends on temperature, salinity and biological productivity. CO2 flux into/out of ocean depends on air-sea CO2 difference. CO2 from A to O CO2 from O to A

41. How do you get surface water down to the deep?

42. Surface Ocean Deep Cold Ocean Upwelling Deep Water Formation Recall:total turnover time of ocean = 1000 years Surface Ocean residence time = 100 years Deep Cold Ocean residence time ~ 1000 years Recall: Residence time is the average amount of time a substance (in this case water) spends in a reservoir

43. Recall: Global Ocean “Conveyor Belt” circulation

44. So, if ocean is taking up CO2 at surface, ~ how long would it take to “fill up”? (reach its capacity)

45. Relative reserv. sizes Ultimately- way more C in fossil fuels vs. what ocean can absorb.. The “passive (physical) CO2 pump is effective- but its slow.

46. b) The “biological pump” (“active” pump, due to biological production and remineralization)

47. Biological uptakeMuch, Much faster than 1000yrs!

48. autotrophs heterotrophs Recall the 2nd piece of basic C cycling: • 1) Autotrophs: Fixation of C into “organic matter” • 2) Heterotrophs: oxidize C - returns to geosphere via breakdown of organic matter Inorganic matter (oxidized carbon) CO2 Organic matter (reduced carbon) CHO

49. CO2 Biological “Pump” Plankton SURFACE OCEAN Sinking Organic matter (reduced carbon) CHO Heterotrophic bacteria CO2 DEEP OCEAN

50. Ocean “Biological Pump” • 1) Surface Plankton fix carbon • 2) Wastes SINK • 3) Deep bacteria remineralize OM