Global Biogeochemical Cycles
Supporting Information for
Marine Biological Production from In Situ Oxygen Measurements on a Profiling
Float in the Subarctic Pacific Ocean
S. M. Bushinsky1, S. Emerson1
1School
of Oceanography, University of Washington, Seattle, WA, 98105
Contents of this file
Text S1
Figures S1
Additional Supporting Information (Files uploaded separately)
Data Set S1 Argo float data
Introduction
This supporting information includes details on the air calibration method used to correct
float oxygen data and a figure containing the difference between optode measured
oxygen and expected atmospheric oxygen, which was used for the long-term drift
correction of the oxygen data. The corrected float oxygen data and other necessary
data (temperature, salinity, pressure, latitude, and longitude) are in a separate, ASCII
file.
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Text S1.
In situ air calibration of float optode
After each profile, 30 air measurements are taken. Measured air pO2 is compared
to expected atmospheric oxygen (𝑝𝑂2𝑎𝑡𝑚𝑜𝑠 ) calculated from:
(S1)
𝑅𝐻
𝑝𝑂2𝑎𝑡𝑚𝑜𝑠 = (𝑃𝐴𝑡𝑚 − 𝑝𝐻2 𝑂(100)) 𝑋𝑂2
where atmospheric pressure (PAtm) is derived from National Center for Environmental
Prediction (NCEP) reanalysis data, water vapor pressure (pH2O) is calculated based on
measured temperature and salinity (Zeebe and Wolf-Gladrow 2001), relative humidity
(RH, in %) is calculated from NCEP 10 m data corrected to 0.6 m above sea surface in
the same manner as Bittig and Körtzinger (2015), XO2 is the mole fraction of oxygen in
the atmosphere (Glueckauf 1951).
Air measurements were filtered to remove daytime measurements and periods
where the temperature, atmospheric pressure, or measured pO2 were changing rapidly, all
of which created noise in the data. The percent difference between measured and
expected pO2 was calculated (Fig. S1) and a linear regression was fit to the data. The
intercept of the linear regression at the time of deployment is equal to the initial offset
calibration of the optode (dashed line in Fig. S1). This agreed with ship-based Winkler
measurements (Fig. S1, yellow square) taken at the time of deployment to within 0.3%.
The slope of the linear regression represents an optode drift of -0.5% yr-1 during the
deployment.
References
Bittig, H. C., and A. Körtzinger (2015), Tackling oxygen optode drift: Near-surface and
in-air oxygen optode measurements on a float provide an accurate in-situ reference,
J. Atmos. Ocean. Technol., 32, 1536–1543, doi:10.1175/JTECH-D-14-00162.1.
Glueckauf, E. (1951), The Composition of Atmospheric Air, in Compendium of
Meteorology, pp. 3–10, American Meteorological Society, Boston, Massachusetts.
Zeebe, R. E., and D. A. Wolf-Gladrow (2001), CO2 in Seawater: Equilibrium, Kinetics,
Isotopes, Elsevier Oceanogr. Ser., Amsterdam.
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𝑜𝑝𝑡𝑜𝑑𝑒
Figure S1. Percent difference between air measurements (𝑝𝑂2
) from an Argo
oxygen float near Ocean Station Papa and calculated atmospheric oxygen (𝑝𝑂2𝑎𝑡𝑚𝑜𝑠 ).
Red error bars represent the average and SD of 30 measurements for each air period. Air
periods with rapidly changing atmospheric conditions (temperature, pressure, measured
pO2) are not shown, nor are daytime air measurements, which displayed a larger spread
and a bias. The solid black line is a linear regression to the air measurements, with the
intercept at the time of deployment equaling the initial calibration offset (-4.2 ± 0.1%),
represented by the black dashed line. The slope of the linear regression is the optode
sensitivity drift of -0.5% yr-1. Gray area around the regression line indicates ± 1 SD
uncertainty. Yellow square with error bars represents the mean and SD of Winkler
measurements taken near the float just after deployment. Air calibration and Winkler
samples agreed to 0.3%.
Data Set S1. Comma delimited ASCII file containing relevant float data for the study
year (June 2012-2013). Data columns are: date, lat, lon, pressure, temperature, salinity,
oxygen. Oxygen is corrected according to the method detailed in S1.
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