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

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

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

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

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

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

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

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:

Change in photosynthesis Change in photosynthesis 2xCO2 minus preindustrial dust deposition as annual average [units: 10-10 kmol P /day /m3]

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

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

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

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

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

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 •

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