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Hydrography of Chromophoric Hydrography of Chromophoric Dissolved Organic Matter (CDOM) Dissolved Organic Matter (CDOM)
in the Pacific Oceanin the Pacific Ocean
Chantal SwanChantal Swan, David Siegel, Norm Nelson, Craig Carlson, David Siegel, Norm Nelson, Craig CarlsonInstitute for Computational Earth System ScienceInstitute for Computational Earth System Science
University of California Santa BarbaraUniversity of California Santa Barbara
ASLO Aquatic Sciences, Santa Fe, NM 2007ASLO Aquatic Sciences, Santa Fe, NM 2007
Open-ocean CDOM: quick factsOpen-ocean CDOM: quick facts
• CDOM (mCDOM (m-1-1) = light-absorbing fraction ) = light-absorbing fraction of DOM (of DOM (≤≤0.2µm)0.2µm)
• Open-ocean CDOM Open-ocean CDOM ≠≠ DOC 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 processes Modulated by transport processes
• Dominates UVR absorption in oceanDominates UVR absorption in ocean
• CDOM causes measurable bias in satellite Chl estimates CDOM causes measurable bias in satellite Chl estimates Siegel et al. [2005] GRLSiegel et al. [2005] GRL
300 350 400 450 5000
0.05
0.1
0.15
0.2
0.25
Wavelength (nm)
a cdom
(m-1
)
CDOM absorption spectrum
m-1 at 325nm
Global surface distribution of CDOMGlobal surface distribution of CDOM
7-yr. mean CDOM (440nm) from GSM algorithm (SeaWiFS-derived) 7-yr. mean CDOM (440nm) from GSM algorithm (SeaWiFS-derived) Siegel et al. [2005] GRLSiegel et al. [2005] GRL
UCSB Global CDOM Distribution and Dynamics SurveyUCSB Global CDOM Distribution and Dynamics Surveyhttp://www.icess.ucsb.edu/GlobalCDOM/http://www.icess.ucsb.edu/GlobalCDOM/
9 cruises 2003-present: 9 cruises 2003-present: NSFNSF CO CO22/CLIVAR Repeat Hydrography Program/CLIVAR Repeat Hydrography Program
& & NASANASA (D. Siegel, N. Nelson, C. Carlson) (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
A
A F
ront
AAIWNPIW
AA
Front
AAIWNPIW
Pacific CDOM along 150Pacific CDOM along 150°°WW
• Meridional gradient in CDOM upper 3000m• Subtropical S. Pac. CDOM ‘low’ extends to 1000m• Characteristic features of water masses & equatorial upwelling
P16
Pacific CDOM vs. AOU (150°W)Pacific CDOM vs. AOU (150°W)
r2 = 0.88, n=863
(z > 700m)
AOU (μmol/kg)
CD
OM
(m
-1)
P2
Pacific CDOM (zonal 30°N)Pacific CDOM (zonal 30°N)
NPIW
STMW
NPIWCDOM vs. AOU at 30°N
z > 0mr2 = 0.59, n=636
North Atlantic CDOM North Atlantic CDOM 66°W66°WA22
(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
DeepCaribbean
DeepCaribbean
NADW
STMW
STMW
North Atlantic CDOM vs. AOUNorth Atlantic CDOM vs. AOU
r2 = 0.01, n=613
(Pooled data: A16N, A20 & A22)
(z > 700m)
AOU (μmol/kg)
CD
OM
(m
-1)
SummarySummary
• 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.
Thank You: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)