Dhomse, Sandip

Lamarque, J. F.

Long, M.

Plane, John

Sáiz-Lopez, A.

Tagliabue, Alessandro

Völker, Christoph

English

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cosmic dust and thethe oceanic cycle of ironC. Völker1, J. Plane2, S. Dhomse2, J.F. Lamarque3, M. Long3,A. Sáiz Lopez2, A. Tagliabue21Alfred-Wegener-Institut2University of Leeds3NCAR, Boulder4CSIC, Madrid5University of LeedsFEMIP meeting, February 16, 2020Johnson, 2001: based on a globalestimate of cosmic dust deposition,assuming homogeneous distributionJohnson, 2001: based on a globalestimate of cosmic dust deposition,assuming homogeneous distributionWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.ZODIAKAL LIGHTBrownlee, 2016, Elementssolar system contains many smallerparticles, from meteors to dustmost particles are concentrated nearthe ecliptic planezodiakal light: solar light scattered atthese particlesWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.WHERE DOES THE DUST COME FROM?Mann, 2006, Astron. Astrophys. Rev.sources of dust: collisions of larger objects, comet’s tails, extrasolar matterWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.SIZE DISTRIBUTIONPeucker-Ehrenbrink, 2016, Elementsmass flux to earth is dominated by particles smaller than 1 mm (cosmicdust), and by rare impacts of very large meteorsWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.WHAT HAPPENS TO COSMIC DUST?Brownlee, 1985, Ann. Rev. Earth Plan. Sci.typical particle entry speed> 10 km s−1most smaller particlescompletely evaporatebetween 80 and 40 km heightablated material largelyre-condenses as ’metoricsmoke particles’What is cosmic dust? Effect on the ocean Summary, caveats, etc.SOME SURVIVING MATERIALCosmic spherules from the 1873-1876 Challenger expeditionTaylor 2016, Elementsslightly larger particlessurvive as partially moltenmaterialoften found in deep-seasediments as ’cosmicspherules’What is cosmic dust? Effect on the ocean Summary, caveats, etc.COSMIC DUST DEPOSITIONcosmic dust: calculated from meteor ablation; chemical reactions andtransport through the atmosphere (Dhomse et al. 2013)largest deposition in subtropics; relatively homogeneousWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.TERRESTRIAL DUST DEPOSITIONterrestrial dust: dust deposition from Albani et al., 2016, assuming Fe is3.5% of total, and soluble fraction of dust Fe 2%largest deposition downwind of deserts; variation over five orders ofmagnitudeWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.CONTRIBUTION OF COSMIC DUSTcosmic dust contributes more > 50% to total soluble iron flux in parts ofSouthern OceanWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.HOW DOES IT AFFECT FE?difference in DFe between a model run with/without cosmic dustlargest increases where cosmic dust is large and Fe is not limitingoverall, changes are smallWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.HOW DOES IT AFFECT PRIMARY PRODUCTION?difference in NPP between a model run with/without cosmic dustglobal NPP increases by 2%, export by 0.9%What is cosmic dust? Effect on the ocean Summary, caveats, etc.AND WHY THERE?largest where boundaries between Fe and N-limited regions shiftWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.THIS IS ONE MODEL. HOW ABOUT OTHERS?sources [109 g Fe yr−1]model dust sediment hydro cosmic resid time [yr]REcoM 317 271 50 12 69BEC 1223 4825 988 8.1PISCES 1826 1485 631 11.5/15.7(grey: old numbers from Tagliabue et al. 2016, need to check)effect is small because upwelling contributes most Fe in the SouthernOceanhow much of the upwelled iron derives ultimately from cosmic dustdiffers between modelssimilar results obtained in BEC, with shorter residence times; PISCES tocome soonWhat is cosmic dust? Effect on the ocean Summary, caveats, etc.SUMMARY AND OPEN ENDScosmic dust is a significant contribution to soluble Fe deposition inSouthern Oceansome uncertainty in the relative cosmic dust contribution fromuncertainties in terrestrial dust input (especially solubility)effect on dissolved Fe < 0.1 nMSouthern Ocean effect on NPP rather small, because dust is arelatively minor contribution here to Fe supply, compared to verticalupwelling/mixing, shelves, . . .global effect on NPP in % rangeresidence time importantisotopes?

Cosmic dust and the the oceanic cycle of iron

https://epic.awi.de/id/eprint/51566/1/cosmic_dust_femip_feb20.pdf

Cosmic dust and the the oceanic cycle of iron

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