1. Remote input of nutrients in a changing climate
J. Segschneider
Max-Planck-Institut für Meteorologie KlimaCampus, Hamburg
WP 16
CarboOcean final meeting, 5-9 October 2009, Os, Norway

2. Main nutrients addressed
Iron from dust input
Nitrogen from agriculture and fossil fuel burning
Nutrients from rivers
+ nutrients from volcanic eruptions
some cooperation with N. Mahowald, M. Gehlen, H. Feichter, C. Timmreck
involves all compartments of the ESM

3. The dust/iron cycle and climate
Iron is supplied to the ocean from atmospheric dust, which in turn is mobilized from arid land surfaces. Solubility of iron in ocean water differs with distance from dust source - atmospheric chemistry-
Iron is thought to be the limiting nutrient in large areas of the ocean (the Southern Ocean, equatorial Pacific, North-West Pacific)
A model study shows a reduction of dust supply in a 2xCO2 climate by 30% (Mahowald et al., 2006) – does this impact on the carbon cycle?
some cooperation with N. Mahowald, M. Gehlen, H. Feichter, C. Timmreck
involves all compartments of the ESM

4. A simplified view of the marine carbon cycle
Atmosphere 31 42 90
solubility
pump 11
103 92
biological
pump
Plankton
Ocean
dissolved
carbon
Thermocline
dissolved
carbon
Fluxes in
GtC/ Year
Sediment

5. The biological pump NO3 PO4 CO2 DEPTH PO4 NO3 CO2 Fe pump is driven
by nutrients and
solar radiance
Redfield ratio
1 P : 16 N
NO3
CO2
What about iron?
PO4
PO4 NO3
CO2
Bacterial remineralisation

6. The iron cycle
some cooperation with N. Mahowald, M. Gehlen, C. Timmreck(?)
involves all compartments of the ESM
Jickells et al

7. Model test: difference in dust deposition
(2xCO2 climate - present climate)
kg/m2/year*1.e-4
annual mean. dust from mahowald et al 2006 for present climate and 2xCO2 climate (~-30% dust input)
Mahowald et al, 2006 on GR30 grid

8. Difference in oceanic iron concentration (surface)
(2xCO2 dust - present dust )
kmol/m3*1.e-10
annual mean. dust from mahowald et al 2006 for present climate and 2xCO2 climate (~-30% dust input)
after 90 years
ocean only experiment:

9. Change in photosynthesis
Change in photosynthesis 2xCO2 minus preindustrial dust deposition as annual average [units: kmol P /day /m3]

10. Effect on export production
Total change?
2xCO2 minus preindustrial climate dust deposition
[annual average, units 10-6 gC/m2/day]

11. CO2-Flux Difference in atmosphere to ocean net CO2 flux
2xCO2 – preindustrial dust deposition
[annual average, units: 10-7 kmol/m2/day]

12. Impact on Cant uptake Decrease in export production by ~0.4 GtC/a
Around 20% of current oceanic uptake of anthropogenic carbon
Not first order process but not negligible either
some cooperation with N. Mahowald, M. Gehlen, H. Feichter, C. Timmreck
involves all compartments of the ESM
Ongoing Research • oceanic uptake of CO2 • biological feedbacks

13. Further processes Nitrogen from agriculture and fossil fuel burning
Nutrients from rivers
+ nutrients from volcanic eruptions
some cooperation with N. Mahowald, M. Gehlen, H. Feichter, C. Timmreck
involves all compartments of the ESM
Ongoing Research • oceanic uptake of CO2 • biological feedbacks

14. Volcanoes: Pinatubo Carbon Anomaly
ENSO: normally increase in atmospheric accumulation rate (1965, 1972, 1987, 1997)
But when preceeded by volcanic eruption (like major El Nino 1982/83) reduced effect,
For Pinatubo strong decrease in accumultion rate (1992). d13C points to terrestrial biosphere, change in atmospheric oxygen to ocean
J. Sarmiento 1993, Atmospheric CO2 stalled, Nature 365
~1.6 x 1015 g C (Sarmiento, 1993; Watson, 1997)
Future Plans • Volcanic eruptions

15. Do volcanic eruptions have an impact on the marine carbon cycle and a feedback on climate?
can the additional ash/nutrients trigger algae blooms and additional CO2 uptake of the ocean?
does reduced radiation significantly reduce biological production and hence carbon uptake, how does this impact on atmospheric pCO2?
(potential for stabilizing temperature)
is the physical pump affected (colder water?)
status: HAMOCC ready for testing, model code ready to read in additional dust field with different iron content
Future Plans • Volcanic eruptions •

16. N-cycle and climate change
Gruber & Galloway, Nature, 2008
Future Plans • N-cycle and climate change