2. 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

3. Acknowledgements: Data: Katherina Seiter Rick Jahnke 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 IMaRS Web Site: http://imars.usf.edu NASA funded project NNG04GG04G

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

5. 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.

6. SeaWiFS CHL SeaWiFS PAR Photo- period AVHRR SST Bathymetry VGPM Monthly Net Primary Production (Behrenfeld and Falkowski, 1997)

7. NPP and POC flux 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 flux(Z) = 3.523* NPP*Z -0.734

8. Global (flux to bottom) Deep water (flux to bottom) Deep Water (flux to 800 m) Margins (flux to bottom) Margins (flux to 500 m) Net PP [Pg * ] 47.9138.92 8.99 (18%) Flux [Pg]0.930.311.01 0.62 (66%) 0.68 (40%) C buried ** [Pg] 0.150.09 0.06 (40%) Global POC flux analysis Preliminary estimate: Margins account for ~40% C stored annually below thermocline and 40% buried in global ocean sediments from settling POC Pg = 10 15 g ** Assumption: 10% burial efficiency on margins and 30% in deep water

9. New estimates of Burial Efficiency

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

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

12. Organic Carbon AR  Only few stations reported OC AR  AR reported at many depths in sediment  We limited data to upper 0.25m of sediment

13. Estimated Burial Efficiency BE = AR / I

14. Results Average Burial Efficiency (%) RegionNMarginNDeepN Global3912.5135.726 Africa179.51316 Arctic1814.5910.89 South America29.42-- Margin = areas < 2,000 m

15. Results

16. Global (flux to bottom) Deep water (flux to bottom) Deep Water (flux to 800 m) Margins (flux to bottom) Margins (flux to 500 m) Net PP [Pg * ] 47.9138.92 8.99 Flux [Pg]0.930.311.010.620.68 C buried ** [Pg] (0.15) 0.09 (0.09) 0.02 (0.06) 0.06 Global POC flux analysis OC buried in oceans may be much less than previously estimated; Margins account for >70% annual POC flux buried in oceans (prior est. ~40%) Pg = 10 15 g ** Assumption: (10% old) 12% new burial efficiency on margins (30% old) 6% new in deep water

17. 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