An integrative view of the biological carbon pump

1. An integrative view of the biological carbon pump from the surface ocean to the deep sediment Sandra Arndt (s.arndt@bristol.ac.uk)

2. Controls importance of global ocean & sediments as C sink (or source) • temporal sequestration of C in deep ocean (very fast response) • CH2O burial (fast response) • weathering-CaCO3 burial (slow response) • Controls atmospheric O2 • Controls nutrient and O2 distribution in the ocean • Controls size of hydrocarbon reservoirs The biological C pump Sandra Arndt (s.arndt@bristol.ac.uk)

3. Euphotic/ Epipelagic zone (0-200m) 0 yrs CH2O CaCO3 Efficiency of the biological C pump Mesopelagic zone (200-1000m) Export flux 10-1 yrs Fexport=10-20% NPP Fexport=100% NPP Bathypelagic zone (1000-4000m) 0.28-30% Fexport 70% Fexport Abyssopelagic zone (4000-6000m) 103 yrs Deposition flux Sediment (0-103-104m) 50% Fexport <1-5% Fexport 108 yrs <0.3% Fexport 13% Fexport Burial flux Sandra Arndt (s.arndt@bristol.ac.uk)

4. Spatial variability Sandra Arndt (s.arndt@bristol.ac.uk)

5. Primary Production (gC m-2 yr-1) Export Efficiency Peff=Fexport/PP Spatial variability- Global scale Henson et al., 2012 Henson et al., 2012 Sediment TOC (wt%) Transfer Efficiency Teff=F2000m/Fexport Henson et al., 2012 Seiter et al., 2004 Sandra Arndt (s.arndt@bristol.ac.uk)

6. Regional patterns of organic matter quality in surface sediments Spatial variability- Global scale Arndt et al., ESR, in press Sandra Arndt (s.arndt@bristol.ac.uk)

7. Spatial variability- Global scale NO3 flux (mmol m-2 yr-1) Seiter et al., 2005 PO4 flux (mmol m-2 yr-1) Hensen et al., 1998 Sandra Arndt (s.arndt@bristol.ac.uk)

8. Lateral transport Spatial variability- Continental Margin Arndt et al., in press Mollenhauer and Eglinton, 2007 Sandra Arndt (s.arndt@bristol.ac.uk)

9. Marine-dominated inner shelf Spatial variability- Lateral Transport Terrestrial mud dominated mid-shelf mudbelt Starved outer shelf and continental slope Schmidt et al., 2007 Sandra Arndt (s.arndt@bristol.ac.uk)

10. Sediments are the ultimate sediment trap! Spatial Variability- Continental Margin Zabel and Hensen, 2006 (modified from Jahnke, 1990) Sandra Arndt (s.arndt@bristol.ac.uk)

11. Continental Margins-Spatial Variability unpublished data Sandra Arndt (s.arndt@bristol.ac.uk)

12. Temporal variability Sandra Arndt (s.arndt@bristol.ac.uk)

13. Seasonal variability NPP: Low: Equ. low productivity regions High: high latitudes, monsoonal and temperate high productivity regions Temporal variability-Seasonal variability Balance between seasonality of flux and production reverses with latitude Lutz et al., 2007 Sandra Arndt (s.arndt@bristol.ac.uk)

14. Seasonal variability in CH2O input results in a complex benthic response Temporal variability-Seasonal variability Soetaert et al., 1996 Sandra Arndt (s.arndt@bristol.ac.uk)

15. Example: 1. Pliocene-Pleistocene Transition at Bowers Ridge (Beringsea) Temporal variability-Lessons from the past Sandra Arndt (s.arndt@bristol.ac.uk)

16. Inverse diagenetic modeling of sediment porwater profiles… Temporal variability-Lessons from the past …indicates peak in CH2O deposition flux & quality across transition and thus important changes in the functioning of the BCP Wehrmann et al., 2013 Sandra Arndt (s.arndt@bristol.ac.uk)

17. Example: 2. Cretaceous Oceanic Anoxic Event Greenhouse climate, anoxic/sulfidic ocean Temporal variability-Lessons from the past Sandra Arndt (s.arndt@bristol.ac.uk)

18. Temporal variability-Lessons from the past Arndt et al., 2009 Inverse diagenetic modeling of sediment porwater profiles indicates low reactivity (high preservation efficiency) and thus rapid transfer from surface ocean to deep sediment Sandra Arndt (s.arndt@bristol.ac.uk)

19. What causes the spatial-temporal variability? The efficiency of the biological C pump is mainly driven by the production, transport and alteration of POC Sandra Arndt (s.arndt@bristol.ac.uk)

20. Ballasting • Model that partitions sinking CH2O in two fractions: • ballast associated • unassociated What causes the spatial-temporal variability? Sarmiento and Gruber, 2006 Sandra Arndt (s.arndt@bristol.ac.uk)

21. Ballasting • Spatial variability of CaCO3 carrying coefficients What causes the spatial-temporal variability? Wilson et al., 2012 Sandra Arndt (s.arndt@bristol.ac.uk)

22. 2. Ecosystem Structure Effect on transport Effect on quality What causes the spatial-temporal variability? Mayor et al., 2012 Micklasz and Denny, 2010 Sandra Arndt (s.arndt@bristol.ac.uk)

23. 3. Organic matter source and transport High quality: Young marine material Low quality: Old marine material Mix pre-aged, terrestrial material What causes the spatial-temporal variability? Arndt et al., in press Sandra Arndt (s.arndt@bristol.ac.uk)

24. Flux: • Simple power-law expression with constant scaling factor (Martin curve, Martin, 1987): • Limit ability of models to predict response of the BCP to environmental perturbations and climate change • no sediments Representation of the pump in Earth System Models Arndt et al., in press (adapted from lutz et al., 2002) Sandra Arndt (s.arndt@bristol.ac.uk)

25. Biological carbon pump is a complex set of interlinked processes that act along the surface ocean- deep sediment continuum Its functioning and efficiency is highly variable in time and space with important implications for global climate and biogeochemical cycles Existing Earth system models include empirical, highly simplified and decoupled representations of the biological carbon pump that are not related to factors that control the quantity and quality of the flux Conclusions Sandra Arndt (s.arndt@bristol.ac.uk)

26. Thank you! Sandra Arndt (s.arndt@bristol.ac.uk)