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Submesoscale NCP and GPP rates from Underway O 2 / Ar and Triple Oxygen Isotope Measurements. Rachel H. R. Stanley Woods Hole Oceanographic Institution. Primer on Biological Production. NCP = Net Community Production = Net amount of C taken up by ecosystem, should equal export production - PowerPoint PPT Presentation
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Submesoscale NCP and GPP rates from Underway O2/Ar and Triple Oxygen Isotope Measurements
Rachel H. R. StanleyRachel H. R. Stanley Woods Hole Oceanographic InstitutionWoods Hole Oceanographic Institution
• NCP = Net Community Production = Net amount of C taken up by ecosystem, should equal export production
• NPP = Net Primary Production = autotrophic component of NCP only• GPP = Gross Primary Production = total photosynthesis
Primer on Biological Production
• ADVANTAGES– In situ techniques– Integrate over one to two weeks – “Easy” to make measurements so high resolution possible– Includes contribution from DOC– Can be done in underway mode but need some depth info
• PROBLEMS– Rely on gas exchange estimate– What exact time/spatial scale are you measuring?– Have to account for mixing, entrainment, etc.– Doesn’t work well in upwelling regions
Gas Tracers for Measuring PP
Method: NCP from O2 and Ar• Oxygen produced by photosynthesis, consumed by
respiration, but also affected by physics
• Ar is abiotic analogue for O2 because similar physiochemical properties
EIMS for Continuous Measurements• Recent advance: continuous at-sea measurements of O2 and
Ar using an Equilibrator Inlet Mass Spectrometer (EIMS) yield thousands of data points of NCP
EIMS for Continuous Measurements• Recent advance: continuous at-sea measurements of O2 and
Ar using an Equilibrator Inlet Mass Spectrometer (EIMS) yield thousands of data points of NCP
OceanMixed Layer
Wet Lab (at-sea)
EquilibratorCartridge
Quadrupole Mass Spectrometer (QMS)
Measure O2 and Ar
gasfrom
headspace
UnderwayWater
EIMS for Continuous Measurements• Recent advance: continuous at-sea measurements of O2 and
Ar using an Equilibrator Inlet Mass Spectrometer (EIMS) yield thousands of data points of NCP
Two Datasets from the Pacific
From Stanley et al, GBC, 2010
WEP
STP
• Not many variables measured at high enough resolution for comparison with NCP
• Temperature is a measure of physical variability and frontal instabilities
• Correlation analysis is not enough – sections with positive and negative correlation, lags, etc.
NCP and Temperature
From Stanley et al, GBC, 2010WEP
• Power spectra for temperature and O2/Ar similar at low frequency, but differ at high frequency
Power Spectra
• PDF=power density function
• Temperature and O2/Ar differ at scales close to 4 km, similar at scales >10 km
Scales of Variability
• PDF=power density function
• Temperature and O2/Ar differ at scales close to 4 km, similar at scales >10 km
Scales of Variability
Similar variability between NCP and physics
• Kurtosis -- at scales ranging from 8 to 50 km -- shows similar variability of temperature and O2/Ar (and thus NCP)
• Suggests that processes are related physics is “priming the pump” for biology
But to examine link, really need Process Studies!
• GPP = Gross Primary Production = total photosynthetic flux• Mass independent fractionation results in atmospheric 17
different than photosynthetic 17.• Sampled discretely while underway or from niskins
GPP from Triple Oyxgen Isotopes
GPP and NPP• “STP” cruise• GPP and NPP
similar pattern• GPP/NPP ratio
equals 3 to 5 • BUT there are
differences autotrophic respiration (RA), Mehler reaction, or photo-respiration
NPP=GPP-RA
GPP, NPP and NCP• Do I want any text?
NCP=GPP-RA-RH
Energy Flow Diagrams• Diagrams drawn
to scale
• Differences in regions: total amount of energy & its distribution between boxes
• Caveats: measurement uncertainty, VGPM NPP
• NCP can be measured continuously from underway system from O2/Ar ratios
• Submesoscale variability in NCP similar to that in physics
• GPP can be measured discretely from underway water or Niskins
• Combination of GPP, NCP and NPP describe energy flow variations in autotrophic respiration may be important
• NEED some CTD cast samples to correct for entrainment (Nicholson et al, submitted)
Conclusions
Collaborators:– Raf Ferrari (MIT), Michael Bender (Princeton), John
Kirkpatrick (UW)– Captain and crew of R/V Kilo Moana and NOAA ship
Kai’imomoana•Funding Sources:
– NSF Chemical Oceanography– WHOI Penzance Fund for Assistant Scientists
Acknowledgements