Global trends in air-sea CO 2 fluxes based on in situ and satellite products
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Transcript of Global trends in air-sea CO 2 fluxes based on in situ and satellite products
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Global trends in air-sea CO2 fluxes based on in situ and satellite
products
Rik Wanninkhof, NOAA/AOMLACE Ocean Productivity and Carbon Cycle (OPCC)
Workshop - June 6-8,UC Santa Barbara
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Sea surface temperature(SST) Wind speed
CCMP (Cross-Calibrated Multi-Platform wind product)
[Atlas et al., 2011]
Sea-air CO2 Flux = K0 × k × ΔpCO2
Sea-air CO2 Flux = K0 × k × ΔpCO2
[Takahashi et al., 2009]
OPCCOPCC Global Ocean Sea-Air CO2 FluxesMethods:
ΔpCO2 climatologyk660 = 0.251 <u2>
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Wind
k pCO2
Air-Sea CO2Flux
SST
Transport
BiologyWindWaves
BubblesSurfaceFilm
Near SurfaceTurbulence
Bock et al. (1999)
OPCCOPCC Global Ocean Sea-Air CO2 FluxesFactors influencing CO2 flux estimates
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OPCCOPCC Global Ocean Sea-Air CO2 FluxesData coverage T-09 climatology
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A Multi-national Effort:
EnglandUSAFranceNetherlandsGermanySpainChina JapanTasmaniaNorway
And more…
Complete Data Set: 1968–200810M points
Our contribution: 3M points
OPCCOPCC Global Ocean Sea-Air CO2 FluxesSurface Ocean Carbon Atlas (SOCAT)Surface Ocean Carbon Atlas (SOCAT)
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OPCC OPCC Global Ocean Sea-Air CO2 FluxesRemote sensing
Wind: CCMP 6-hr ¼˚
k660 = 0.251 <u2> based on global 14C constraint
Gas transfer velocity
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OPCC Global Ocean Sea-Air CO2 FluxesGlobal 14C constraint
Broecker and Peng (1994)
Transfer velocitykav = 17.5 cm/hru2 = 69.3 (m/s) 2
umean ≈ 7.4 m/s
Semi-infiniteHalf space
Bomb 14C inventory constraintGlobally: a <u2> = Constant
€
a = kav /∑[P(u)un ]
k = aun (Sc /660)−1 2
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OPCC Global Ocean Sea-Air CO2 FluxesRelationship of k and U10
Good agreement with global bomb 14C constraint and local studies
Ho et al. 2011
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Uncertainty in different components of the flux estimate (adapted from section 6, T-09)
Takahashi et al. (2009) RECCAP (2011)Pg C yr-1 % Pg C yr-1 % Pg C yr-1
Net flux -1.4 -1.2 ∆pCO2 ±0.18 ±13% ±0.18 k ±0.42 ± 30% ±0.2Wind (U) ±0.28 ± 20% ±0.2 <pCO2w/dt>a ±0.5 ± 35% ±0.5 Total ±0.7 ± 53%. ±0.6 Under-sampling bias -0.2 -0.2Pre-industrial sea-air flux 0.4 ± 0.2 0.4 ± 0.2Anthropogenic CO2 flux -2.0 ± 1.0 -1.8 ± 0.8
OPPCOPPC Sea-Air CO2 FluxesClimatological Magnitude and Uncertainty
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dpCO2 =∂pCO2
∂T
⎛
⎝ ⎜
⎞
⎠ ⎟dT +
∂pCO2
∂TCO2
⎛
⎝ ⎜
⎞
⎠ ⎟dTCO2 +
∂pCO2
∂TALK
⎛
⎝ ⎜
⎞
⎠ ⎟dTALK +
∂pCO2
∂S
⎛
⎝ ⎜
⎞
⎠ ⎟dS
Temperature (C) -2 –30 (ln pCO2/T) = 0.0423oC-1 400%
Variable Range Relation Effect
TCO2(mol kg-1) 1900-2200 (ln pCO2/Tln TCO2) = 10 400%
Alkalinity(mol kg-1)* 2150-2350 (ln pCO2/Tln TALK) = -9.4 -200%
Salinity(mol kg-1)* 33.5-37 (ln pCO2/Tln S) = 0.94 ~10%
*Alkalinity and salinity are proportional and can be accounted for
OPCC Global Ocean Sea-Air CO2 FluxesFactors influencing surface water pCO2
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Annual uptake of anthropogenic CO2 since 1960 from models. The absolute uptake (solid line, left axis) has increased over time while the fraction of uptake (=ocean uptake/fossil fuel CO2 release *100) (dashed line, right axis) has decreased. Data are obtained from http://lgmacweb.env.uea.ac.uk/lequere/co2/carbon_budget.htm (Le Quéré et al., 2009).
OPPCOPPC Sea-Air CO2 Fluxes: Model and atm. based estimates of trends
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OPCCOPCC Sea-Air CO2: Flux variabilityTrends
Fym = kym K0 ym {[ΔpCO2 2000m + (δpCO2SW / δSST)2000m × ΔSSTym – 2000m] },
(δpCO2SW / δSST)2000m : Optimal subannual relationships for each 4˚ by 5˚ grid box
Park et al. Tellus B 2010:Variability of global net sea-air CO2 fluxes over the last three decades using empirical relationships
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The linear regressions (solid line) for the flux are 0.009± 0.005 Pg C yr-1, respectively. The 20-years mean values for the flux is -1.12± 0.13 Pg C, respectively.
Decrease in uptake due to winds and SST feedbacks
OPCCOPCC Sea-Air CO2 Fluxes Trends 1980-1999
Sea-air CO2 Flux = K0 × k × ΔpCO2
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OPCC OPCC Global Ocean Sea-Air CO2 FluxesRemote sensing
How can we quantify the impact of [remotely measured] biological processes on ∆pCO2?
Regional approach Multi-sensor Melding in situ and remotely sensed information
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Annual uptake of anthropogenic CO2 since 1960 from models. The absolute uptake (solid line, left axis) has increased over time while the fraction of uptake (=ocean uptake/fossil fuel CO2 release *100) (dashed line, right axis) has decreased. Data are obtained from http://lgmacweb.env.uea.ac.uk/lequere/co2/carbon_budget.htm (Le Quéré et al., 2009).
OPCCOPCC Sea-Air CO2 Fluxes: IPCC estimates
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Figure 4. Zonal wind comparison of several global wind products for the year 2000. The differences of up to 2 m/s are observed but the biases are not always consistent between high and low latitudes. (Figure courtesy of C. Sweeney) .CCMP = Cross Calibrated Multi-Platform winds (Atlas et al., 2011); ECWMF =European Center for Medium Weather Forecasting; NCEP = National Center for Environmental Prediction; QSCAT = QuikSCAT polar orbiting satellite with an 1800 km wide measurement swath on the earth's surface equipped with the microwave scatterometer SeaWinds
OPCCOPCC Sea-Air CO2: Global Winds