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Submesoscale NCP and GPP rates from Underway O 2 / Ar and Triple Oxygen Isotope Measurements

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

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Submesoscale NCP and GPP rates from Underway O 2 / Ar and Triple Oxygen Isotope Measurements

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  1. Submesoscale NCP and GPP rates from Underway O2/Ar and Triple Oxygen Isotope Measurements Rachel H. R. StanleyWoods Hole Oceanographic Institution

  2. Primer on Biological Production • 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

  3. Gas Tracers for Measuring PP • 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

  4. 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

  5. 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

  6. 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 Wet Lab (at-sea) Quadrupole Mass Spectrometer (QMS) Measure O2 and Ar gas from headspace Equilibrator Cartridge Underway Water Ocean Mixed Layer

  7. 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

  8. STP Two Datasets from the Pacific WEP From Stanley et al, GBC, 2010

  9. NCP and Temperature • 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. WEP From Stanley et al, GBC, 2010

  10. Power Spectra • Power spectra for temperature and O2/Ar similar at low frequency, but differ at high frequency

  11. Scales of Variability • PDF=power density function • Temperature and O2/Ar differ at scales close to 4 km, similar at scales >10 km

  12. Scales of Variability • PDF=power density function • Temperature and O2/Ar differ at scales close to 4 km, similar at scales >10 km

  13. 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!

  14. GPP from Triple Oyxgen Isotopes • GPP = Gross Primary Production = total photosynthetic flux • Mass independent fractionation results in atmospheric 17D different than photosynthetic 17D. • Sampled discretely while underway or from niskins

  15. GPP and NPP NPP=GPP-RA • “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

  16. GPP, NPP and NCP NCP=GPP-RA-RH • Do I want any text?

  17. Energy Flow Diagrams • Diagrams drawn to scale • Differences in regions: total amount of energy & its distribution between boxes • Caveats: measurement uncertainty, VGPM  NPP

  18. Conclusions • 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)

  19. Acknowledgements 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

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