The O2/N2 Ratio and CO2 Airborne
Southern Ocean Study
(ORCAS)
Principal Investigators:
Britton Stephens and Matthew Long
(National Center for Atmospheric Research)
Ralph Keeling (Scripps), Colm Sweeney (U. Colorado),
Eric Kort (U. Michigan)
Collaborative science team:
Nikki Lovenduski, and David Munro (U. Colorado);
Michelle Gierach (JPL); Heidi Dierssen (U. Connecticut);
Hugh Ducklow (LDEO); Scott Doney (WHOI); Nicolas Cassar (Duke);
Oscar Schofield (Rutgers); Andy Thompson (CalTech);
Jorge Sarmiento (Princeton); Sue Schauffler and Eric Apel (NCAR/ACD);
Elliot Atlas (U. Miami); Jorgen Jensen (NCAR/EOL)
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1
Southern Ocean air-sea fluxes: model uncertainty
CMIP5 modeled air-to-sea CO2 fluxes
Sink
Source
PgC/month
Obs
Anav et al. 2013
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2
CO2 flux is a small residual of opposing terms; O2 flux is not
Sea-to-air fluxes
Obs.
Obs.
CMIP5 CO2 fluxes
Anav et al. 2013
CO2 flux
drivers
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O2fluxes
S. Mikaloff-Fletcher
O2 flux
drivers
3
NSF/NCAR HIAPER Gulfstream V
High-performance Instrumented Airborne Platform for Environmental Research
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4
Hemispheric scale O2 plume
Meridional section: O2 in Austral Summer
courtesy of B. Stephens
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O2 /N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS)
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Research questions
What are the magnitudes and interrelationships of summertime air-sea O2 and
CO2 fluxes over the Southern Ocean at regional to zonal scales?
What are the dominant processes driving the seasonal evolution and spatial
variability in these fluxes?
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7
ORCAS Jan–Feb 2016?
Core measurement objectives
I
Large-scale O2 and CO2 distributions: 50◦ S–70◦ S, 0–14km;
I
Vertical O2 :CO2 ratios across boundary-layer top and through
mid-troposphere;
I
O2 and CO2 fluxes inferred from Lagrangian particle dispersion
back-trajectories: (1) regional scale, using upwind/downwind flights 30-hr
apart, (2) whole campaign.
GV Scientific Payload
Instrument
Airborne Oxygen Instrument (AO2)
Quantum Cascade Laser Spectrometer(QCLS)
Picarro
Medusa Flask Sampler
Portable Remote Imaging Spectrometer (PRISM)
Advanced Whole Air Sampler (AWAS)
HIAPER Trace Organic Gas Analyzer (TOGA)
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Measurement
δ(O2 /N2 ), CO2
CO2 , CH4 , N2 O, CO
CO2 , CH4 , H2 O
δ(O2 /N2 ), CO2 , δ(Ar/N2 ), δ 13 C,
δ 18 O, and ∆14 C of CO2
Hyperspectral water-leaving
radiance
Over 80 trace gases, including
DMS, OCS, halocarbons,
MeONO2 , isoprene
Over 60 VOCs, including nitrate
species, DMS, and VSL
halocarbons
Institution
NCAR EOL
Harvard/Aerodyne/NCAR
NOAA/CU
NCAR/Scripps
JPL
NCAR/U. Miami
NCAR
8
Earth system models used for hypothesis testing
0
6
gazing incr.
d−1]
wind-stress incr.
gazing
reduced
−5
Bioavail.
Fe incr.
−10
CO2 Flux
0
Source
O
A
J
J
Sink
−1
d ]
−2
CO2 flux [mmol m
20
0
−20
J
MM
M
A
M
O
S
0
Source
Source
S
A
J
O
O
S
O
S
AS
MA
A
J
JJJJ
J
M
M
−4
N
NN
−60
−12
J
A
S
O
N
D
J
F
M
A
M
J
D
grazing
increased
D
◦
M
−40
D
F
F
FF
M
MM
A
> 60 S
−60
D
J
J
J
−8
−10
80−90W (S)
Enhanced
winter mixing
AA
control
D
D
N
M
−6
−40
D
N
J
N
N
grazing
reduced
Sink
−2
D
control
Sink
Sink
J
N J JJ
O
Source
grazing
increased
F
F
F
M
A
O A
A
MMM
JJ
J
F
< 60◦ S
2
40
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J
SS
AA
4
O2 Flux
60
J
−2
−4
6
80
O flux [mmol m−2 d−1]
2
No Fe lim.
O
A
2
80−90W (N)
Enhanced
winter mixing
S
4
CO2 flux [mmol m
−2
PI-slope
2
CO flux [mmol m−2 d−1]
8
Vertical mix. param. change
5
A
grazing
reduced
−20
0
20
40
O2 flux [mmol m−2 d−1]
60
9
Synergistic opportunities
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I
Palmer LTER cruise and ∆O2 /Ar sampling aboard the L.M. Gould
I
SOCCOM biogeochemical profiling floats
I
Gliders?
I
others?
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