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. The biological C pump Controls importance of global ocean & sediments as C sink (or source) temporal sequestration of C in deep ocean (very fast response) CH 2 O burial (fast response) weathering-CaCO 3 burial (slow response) Controls atmospheric O 2 Controls nutrient and O 2 distribution in the ocean Controls size of hydrocarbon reservoirs

3. Sandra Arndt (s.arndt@bristol.ac.uk) Efficiency of the biological C pump Euphotic/ Epipelagic zone (0-200m) F export =10-20% NPP 10 -1 yrs 10 3 yrs Deposition flux Sediment (0-10 3 -10 4 m) Mesopelagic zone (200-1000m) Bathypelagic zone (1000-4000m) Abyssopelagic zone (4000-6000m) 0 yrs 10 8 yrs 0.28-30% F export <1-5% F export <0.3% F export CH 2 O F export =100% NPP Burial flux 70% F export 50% F export 13% F export CaCO 3 Export flux

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

5. Sandra Arndt (s.arndt@bristol.ac.uk) Spatial variability- Global scale Henson et al., 2012 Seiter et al., 2004 Primary Production (gC m-2 yr-1)Export Efficiency P eff =F export /PP Transfer Efficiency T eff =F 2000m /F export Sediment TOC (wt%)

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

7. Sandra Arndt (s.arndt@bristol.ac.uk) Spatial variability- Global scale Seiter et al., 2005 Hensen et al., 1998 PO 4 flux (mmol m-2 yr-1) NO 3 flux (mmol m-2 yr-1)

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

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

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

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 Sandra Arndt (s.arndt@bristol.ac.uk) Continental Margins-Spatial Variability unpublished data

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

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

14. Sandra Arndt (s.arndt@bristol.ac.uk) Temporal variability-Seasonal variability Soetaert et al., 1996 Seasonal variability in CH 2 O input results in a complex benthic response

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

16. Sandra Arndt (s.arndt@bristol.ac.uk) Temporal variability-Lessons from the past Wehrmann et al., 2013 Inverse diagenetic modeling of sediment porwater profiles… …indicates peak in CH 2 O deposition flux & quality across transition and thus important changes in the functioning of the BCP

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

18. Sandra Arndt (s.arndt@bristol.ac.uk) 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

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

20. Sandra Arndt (s.arndt@bristol.ac.uk) What causes the spatial-temporal variability? 1.Ballasting Model that partitions sinking CH 2 O in two fractions: 1)ballast associated 2)unassociated Sarmiento and Gruber, 2006

21. Sandra Arndt (s.arndt@bristol.ac.uk) What causes the spatial-temporal variability? 1.Ballasting Spatial variability of CaCO3 carrying coefficients Wilson et al., 2012

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

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

24. Sandra Arndt (s.arndt@bristol.ac.uk) Representation of the pump in Earth System Models Arndt et al., in press (adapted from lutz et al., 2002) 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

25. Sandra Arndt (s.arndt@bristol.ac.uk) Conclusions 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

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