Organic Carbon Flux and Burial Efficiency in the

Organic Carbon Flux and Burial Efficiency in the Global Ocean Remy Luerssen, Frank Müller-Karger, Chuanmin Hu University of South Florida, College of Marine Science

Acknowledgements: Data: Katherina Seiter NASA funded project Rick Jahnke NNG 04 G NASA US Navy NGDC JGOFS PANGAEA ORFOIS WOCE/WOA USGS Atlantic Continental Margins Program Comments and guidance: Rick Jahnke Larry Mayer David Hollander Mike Pace Jon Cole IMa. RS Web Site: http: //imars. usf. edu

PURPOSE OF STUDY ©How much carbon fixed by marine photosynthesis is sequestered in the ocean? ©What is the burial efficiency of ocean sediments?

Average annual POC flux [g C m-2 y-1] to bottom of the ocean (1998 – 2001) Muller-Karger et al. 2005. The importance of continental margins in the global carbon cycle. GRL, Vol. 32.

Sea. Wi. FS CHL AVHRR SST Sea. Wi. FS PAR Bathymetry Photoperiod VGPM Monthly Net Primary Production (Behrenfeld and Falkowski, 1997)

NPP and POC flux(Z) = 3. 523* NPP*Z-0. 734 Pace, M. , G. Knauer, D. Karl and J. Martin. (1987) Primary production, new production and vertical flux in the eastern Pacific Ocean. Nature. 325, 803 -804

Global POC flux analysis Global (flux to bottom) Deep water (flux to bottom) 47. 91 38. 92 Flux [Pg] 0. 93 0. 31 C buried ** [Pg] 0. 15 0. 09 Net [Pg*] PP • Pg = 1015 g Deep Water (flux to 800 m) Margins (flux to bottom) 8. 99 (18%) Margins (flux to 500 m) 1. 01 0. 62 (66%) 0. 68 (40%) 0. 06 (40%) ** Assumption: 10% burial efficiency on margins and 30% in deep water Preliminary estimate: Margins account for ~40% C stored annually below thermocline and 40% buried in global ocean sediments from settling POC

New estimates of Burial Efficiency

©Method: ©Estimates of POC flux (I) from satellite data + model ©Sediment database on accumulation rates (AR) Burial Efficiency (BE) = AR / I

Accumulation Rate Measurements [Database: Origin and fate of biogenic particle fluxes in the ocean (ORFOIS)]

Organic Carbon AR ØOnly few stations reported OC AR ØAR reported at many depths in sediment ØWe limited data to upper 0. 25 m of sediment

Estimated Burial Efficiency BE = AR / I

Results Average Burial Efficiency (%) Region N Margin N Deep N Global 39 12. 5 13 5. 7 26 Africa 17 9. 5 1 3 16 Arctic 18 14. 5 9 10. 8 9 2 9. 4 2 -- -- South America Margin = areas < 2, 000 m

Results

Global POC flux analysis Global (flux to bottom) Deep water (flux to bottom) 47. 91 38. 92 Flux [Pg] 0. 93 0. 31 C buried ** [Pg] (0. 15) (0. 09) Net [Pg*] PP • Pg = 1015 g 0. 09 0. 02 Deep Water (flux to 800 m) Margins (flux to bottom) Margins (flux to 500 m) 8. 99 1. 01 0. 62 0. 68 (0. 06) 0. 06 ** Assumption: (10% old) 12% new burial efficiency on margins (30% old) 6% new in deep water OC buried in oceans may be much less than previously estimated; Margins account for >70% annual POC flux buried in oceans (prior est. ~40%)

Conclusions © BE shows high variability around globe © Only few AR and flux measurements available © Burial efficiency seems greater on continental margins than in deep ocean © Margins may account for >70% annual POC burial © Next steps: © Identify additional flux and sediment data © Look at relationship with other ocean and sediment characteristics