1. Hydrography of Chromophoric Dissolved Organic Matter (CDOM) in the Pacific Ocean Chantal Swan, David Siegel, Norm Nelson, Craig Carlson Institute for Computational Earth System Science University of California Santa Barbara ASLO Aquatic Sciences, Santa Fe, NM 2007

2. Open-ocean CDOM: quick facts CDOM (m -1 ) = light-absorbing fractionCDOM (m -1 ) = light-absorbing fraction of DOM (≤0.2µm) of DOM (≤0.2µm) Open-ocean CDOM ≠ DOCOpen-ocean CDOM ≠ DOC Net produced through microbial processing of DOC & POCNet produced through microbial processing of DOC & POC Destroyed by sunlight (photobleaching) in surface oceanDestroyed by sunlight (photobleaching) in surface ocean Modulated by transport processesModulated by transport processes Dominates UVR absorption in oceanDominates UVR absorption in ocean CDOM causes measurable bias in satellite Chl estimatesCDOM causes measurable bias in satellite Chl estimates Siegel et al. [2005] GRL Siegel et al. [2005] GRL CDOM absorption spectrum m -1 at 325nm

3. Global surface distribution of CDOM 7-yr. mean CDOM (440nm) from GSM algorithm (SeaWiFS-derived) Siegel et al. [2005] GRL

4. UCSB Global CDOM Distribution and Dynamics Survey http://www.icess.ucsb.edu/GlobalCDOM/ 9 cruises 2003-present: NSF CO 2 /CLIVAR Repeat Hydrography Program 9 cruises 2003-present: NSF CO 2 /CLIVAR Repeat Hydrography Program & NASA (D. Siegel, N. Nelson, C. Carlson) & NASA (D. Siegel, N. Nelson, C. Carlson) 4 cruises 2005-present: Equatorial BOX Project (M. Behrenfeld et al.) 4 cruises 2005-present: Equatorial BOX Project (M. Behrenfeld et al.) Eq. BOX

5. AA Front AAIW NPIW AA Front AAIW NPIW Pacific CDOM along 150°W Meridional gradient in CDOM upper 3000m Subtropical S. Pac. CDOM ‘low’ extends to 1000m Characteristic features of water masses & equatorial upwelling P16

6. Pacific CDOM vs. AOU (150 ° W) SALINITY [psu]

7. Pacific CDOM vs. AOU (150°W) r 2 = 0.88, n=863 (z > 700m) AOU (μmol/kg) CDOM (m -1 )

8. P2 Pacific CDOM (zonal 30°N) NPIW STMW NPIW CDOM vs. AOU at 30°N z > 0m r 2 = 0.59, n=636

9. North Atlantic CDOM 66°W A22 (Nelson et al. in press DSR-I) Low variability in CDOM in deep waters Relatively rapid advection (NADW) = dominant process in N. Atlantic basin Strong STMW signal – photobleached surface waters entrained NADW STMW AAIW Deep Caribbean Deep Caribbean NADW STMW

10. North Atlantic CDOM vs. AOU r 2 = 0.01, n=613 (Pooled data: A16N, A20 & A22) (z > 700m) AOU (μmol/kg) CDOM (m -1 )

11. Summary The relative importance of net CDOM production vs. ventilation determines the CDOM-AOU relationship. The ratio of CDOM production rate to ventilation rate controls the basin-scale CDOM patterns observed.

12. Thank You: Funding Programs: NSF Chemical Oceanography NASA Ocean Biology and Biogeochemistry NASA Earth System Science Fellowship Program Repeat Hydrography chief scientists & field teams A. Mishonov (TAMU) D. Hansell, S. Brown, W. Chen (RSMAS) D. Menzies, E. Wallner, M. Meyers, S. Goldberg, J. Klamberg, K. Ireson, T. Westberry (UCSB)

13. Global CDOM ≠ DOC CDM DOC Siegel et al. [2002] JGR

14. Surface CDOM & SeaWiFS A16N A20 A22 r 2 = 0.65; N = 111 slope = 1.16 Siegel et al. [2005] JGR