Aug/Sept 2006
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Transcript of Aug/Sept 2006
Aug/Sept 2006
Equator
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Iron, Aluminum and Manganese in the Equatorial Pacific
James W. MurrayLia SlemonsJoe Resing (NOAA/PMEL)Barbara PaulUniversity of Washington
AGU JOINT Assembly 2009
How did I get into this…Always a Voyage to Address the MostImportant Questions.
Fellow Citation: Surface Chemistry of MnO2, FeOOH and Natural Marine Particles (Stumm, Balistrieri, Dillard)
234Th as a Tracer for Ocean Scavengingthen Export Production, sediment traps w/234Thand 15N-New Production (Anderson, Dunne, Wei, Aufdenkampe)
Models of Controls on New/Export ProductionFood Web Structure and Parameterization of Grazing (Frost, Lukos)
Iron as a Control on Export Production ( Johnson, Slemons)
Stay Tuned – Stable Iron Isotopes as a Tracerfor the Source of Iron
Is the Main Flux of Fe from the EUC?
Gordon and Coale (1995)
An EqPac Hypothesis: The Equatorial Pacific HNLC
NO3
Is thereA maximum?
Mackey et al. (2002)Depth profiles of total dissolvable Fe
Stations sampled – R/V Kilo Moana 0625
Aug/Sept 2006Honolulu to Rabaul
Equatorial Undercurrent during Kilo 0625
ADCP From P. Dutrieux(Hawaii)
ө(EUC) =25.0 to 25.5
EUC – 61% NGCUC at 145ENICU – ~10% at 156E
From P. Dutrieux(Hawaii)
Equatorial Zonal SectionsnM
Papua New Guinea (145E) Meridional Section
Fe
Mn
Al
Vitiaz 2N, 145E Currents at 200 m, P. Dutrieux
nM
Fe max : west Pacific
Key Features of Observations
• There are maxima for Fe, Al and Mn with the EUC.
The Al maximum correlates best with the EUC.
The Fe maximum is 50-100m deeper. • Fe and Mn maxima in EUC are mostly
particulate• Al in EUC is dissolved• Concentrations of Fe, Al and Mn in the EUC
increase to the west• High surface values for dissolved Al and Mn in
the west, but not for Fe. Al and Mn concentrations decrease from west to east
AlD and FeD along Section P16 (150W) in the Pacific
Hiscock, Measures and Landing 2009
New Hypothesis: Variability in Iron and ProductivityENSO variability in strength and depth of NGCUC Ryan et al (2006)
Future work – we need to understand
• What controls the details of the distributions 1. Why is the surface maxima for Al and Mn (mostly
dissolved) but not for Fe? Is it river, atm origin? 2. Why is the EUC maximum for Al shallower than for Fe?
Why are EUC maxima for Fe mostly particulate but Al is dissolved? Are these from Sediment sources? 3. How (where) does the NGCUC connect to the EUC?
• Is there seasonal variability of Fe to the NGCUC that corresponds to variable speed and depth of the NGCUC?
• Northern end-member (Marianas to Mindanau to NECC)?• Stable Iron Isotopes to Distinguish Between Riverine Versus Sediment
Resuspension
ToolsTools : : Models
OPA PI SCES
PO43-
Diatoms
MicroZoo
P.O.M
D.O.M
Si
I ronNano-phyto
Meso Zoo
NO3-
NH4+
Small Big
Euphotic Layer (10-200m)
OPA-PISCES Model
0.5˚ meridional * 2˚ zonal31 vertical levels, 12 in upper 120m
Model iron sources in the western equatorial Pacific
Subsurface dissolved iron at 140°W
Surface nitrate concentrations and primary productivity shifts
Surface chlorophyll
Conclusions of Model Study:
There is a Maximum of Iron in the EUC
It is primarily in the Acid Solublele Particulate PhaseA Dissolved Iron Maximum is not Apparent
If the Acid Soluble Iron is Considered to beBioavailable if results in Unrealistic Model Biological Fields(NO3 too low; Chl too high)
Thus, There is a Source of Iron from the EUC but it isMostly not Bioavailable
10L Go-Flo Trace Metal Rosettewith Vectran conducting cable ontrace metal clean winch.
Sample processing in lab “bubble”
Canadian GeotracesTrace Metal Sampling system
Sampling Methods
Analytical Methods
• Flow Injection Analysis– Fe chemiluminesence
• detection limit 0.06 nM (3*rsd ZLT blank, 4 min load)• Precision of 0.5 nM internal standard: 0.09 nM
– Al fluorometric • detection limit 0.15 nM with 1-min load• 3.5% precision
– Mn colorimetric• Detection limit 0.050 nM • 4% precision cruise replicates
• Internal, external Standards– 3 x 2L internal standard– SAFe external standard: 0.12 0.012 nM,
within 1 rsd of consensus value of 0.097 nMLia in lab
Vitiaz to NGCUC (before Sepik)
NGCUC (after Sepik) to 145E ; 0.6N
Fe max: central Pacific
Schematic of PISCES iron cycle
Zonal sections of iron and nitrate along the equator
Meridional structure of primary productivity
Patterns of POC export
Thermocline iron and surface nitrate trends