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

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