Marine biology and geochemistry in Earth System Models Andrew Watson School of Environmental Science University of East

1. Marine biology and geochemistry in Earth System Models Andrew Watson School of Environmental Science University of East Anglia Norwich NR4 7TJ UK

2. Major effects of marine biology on the Earth system. • “Biological pump” for atmospheric CO2 - sets natural atmospheric CO2 on time scales 102 – 105 years. • Sulphur gas impact on cloud albedo via CCN production. • Production of sediments – carbonate sink and organic carbon sink. • Major influence on atmospheric CO2 and O2 over millions of years.

3. Why do you need biology and geochemistry in earth system models? • Studies of the long-term habitability of the earth: • Faint young sun • major glaciations • Sudden warmings • Response to major impact events

5. Solar output Atmosphericgreenhouse surface temperature The Dim young sun: evolution of atmosphere and solar output time

6. Weathering of rock: CO2 + XSiO3= XCO3+SiO2 Weathering of organics: CH2O+O2 = CO2 + H2O Burial of organics: CO2 + H2O = CH2O+O2 Ocean Oceanic crust Metamorphism of rock; XCO3+SiO2=CO2 +XSiO3 Weathered sediment from continents Long term (>105 year) concentrations of atmospheric CO2, O2, CH4 etc are set by biota-geochemical interactions.

7. Quaternary Permo-Carboniferous Ordovician Neoproterozoic Paleoproterozoic Major glaciations • Some (or all?) may be related to changes in greenhouse gases, driven by biological change.

8. A Neoproterozoic Snowball Earth?

9. Why do you need marine biology and geochemistry in earth system models? • Studies of the long-term habitability of the earth • The Quaternary climate: the classic Earth system problem. • CO2 changes are largely ocean-driven. • Cannot be correctly modelled without representation of • short-term processes (e.g. air-sea exchange • Long-term processes (sedimentary accumulation and dissolution).

10. CO2: controlled by ocean chemistry, biology,circulation? Deuterium in ice: proxy for local temperature Vostok core proxies Methane:sourced from wetlands? Atmospheric dust: signal “leads” other indicators Sea-salt sodium: proxy for wind strength? Atmospheric d18O: proxy for biosphere productivity? The driver? Summertime insolation, N. hemisphere Source: Petit, J.R. et al., 1999. Nature,399: 429-436.

11. Why do you need marine biology and geochemistry in earth system models? • Studies of the long-term habitability of the earth • The Quaternary climate: the classic Earth system problem. • Short term (~100 year) feedbacks on global change…

12. Possible Marine biological effects on carbon uptake, next 100 years. Process Effect on CO2 uptake • Iron fertilisation or change in atmospheric iron supply. • NO3 fertilisation • pH change mediates against calcite-precipitating organisms • Reduction in overturning circulation interaction with nutrient utilisation • Other unforeseen ecosystem changes ?

13. Modelling the marine ecosystem in ESMs • Complex ecosystem – too costly (and not enough knowledge) to model at species level. • Simple models, “NPZD” – single nutrient, primary producer, consumer. • More complex, “functional groups” of phytoplankton, size classes of zooplankton.

14. Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

15. 10m Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need lower Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

16. 10m Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

17. 10m Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

18. 10m Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

19. 10m Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

20. Biogeochemical functional groups • Nutrients • NO3, PO4, Si, Fe • Phytoplankton Fix carbon • Diatoms “large”, need Fe, NO3, Si. • Non-Diatoms “small”, need Fe, NO3 • Coccolithophores produce CaCO3 • Phaeocystis produce DMS • Others • Zooplankton • Mesozooplankton Eat everything, produce large sinking flux • Microzooplankton Eat small phytoplankton, produce small sinking flux • Bacteria • Viruses

21. Nitrate concentrations in surface water – the “HNLC” regions Annual mean surface nitrate, mol kg-1

22. Annual average chlorophyll

23. In all the HNLC regions, iron release experiments have now shown that diatom blooms are stimulated by addition of iron. These depress surface CO2 and nutrients. Why? Large cells such as diatoms have small surface-to-volume ratio. Their growth is limited at low Fe concentrations by rate of diffusive transport of Fe into the cell.

24. Effect of iron on HNLC ecosystems Large-cell system small-cell system -inefficient recycling -efficient recycling -substantial export -little particle export Strongly iron-limited Weakly iron-limited "large" "small" phyto- phyto- plankton plankton nut- rients meso- micro- zoo- zoo- plankton plankton

25. gas exchange remineralization Two-component plankton biogeochemistry – BIOGEM (Ridgwell) aeolian dust deposition e temperature + insolation dissolution atmospher un-off non-diatom diatom r productivity productivity ocean surface continental scavenging ior inter dissolution ocean sedimentation sedimentary diagenesis sediments burial Fe C dust KEY: CaCO PO Si 3 4

26. PISCES model (Bopp et al., 2003).

27. Dust/marine biology/CO2 climate feedback in the earth system.

30. f1 : temperature  dust Data from the Vostok ice core.

31. f2 : dust  atmospheric CO2 • Marine biological effect: results of two different models and a hypothetical response Bopp et al Ridgwell

32. f3 : atmospheric CO2 temperature. • Use climate sensitivities for glacial – interglacial cycle from models, 2ºC antarctic temperature change for 200-280 ppm CO2 change.

33. 

34. Conclusions • Simple marine biology sub-models for earth system models now exist. • First order effects on climate dynamics over periods > 102 years. • Magnitude of effects uncertain. • To do list: