Coastal CO2 fluxes from satellite ocean color, SST and winds
Pete Strutton
CIOSS / College of Oceanic and Atmospheric Sciences
Oregon State University
1. The coastal ocean as a CO2 sink (?)
2. Magnitude and variability of fluxes
3. Quantifying fluxes via satellite
 GOES-R Risk Reduction
Coastal CO2 Fluxes
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pCO2 in the coastal environment (and the equatorial regions for
that matter) is associated with characteristic chlorophyll and SST
signatures.
Using techniques such as multiple linear regression, it should be
possible to determine sea surface pCO2 from space.
Combining this with winds from either scatterometer(s) or
coastal/buoy meteorological stations will facilitate flux
calculations.
Important: In many areas we don’t even know the sign of the flux.
Coastal ocean important for quantifying terrestrial fluxes.
NO3
NO3 gradient
Turbulent eddy-diffusion
NO3 flux
Characteristics of the Oregon upwelling system
What are the important properties that make this region a CO2 sink?
• Strong (but episodic) upwelling throughout summer.
• Extremely rapid depletion of NO3 and CO2.
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NO3 depleted from ~34 M to essentially zero over ~10km
Corresponding drawdown of CO2 from ~600 to 200ppm
Low concentrations offshore persist, despite variability nearshore
Mean along-transect CO2 concentration typically ~300ppm
Implies CO2 ~70ppm (as much as 150ppm on some transects)
Minimal warming of the upwelled waters (cf California?)
What is the magnitude of the sink?
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Assume the conditions off Oregon are characteristic of upwelling
regions along the entire west coast.
Assume an upwelling season from May to August.
Carbon sink is ~0.02 Pg C, approx. 5% of the annual mean North
Pacific sink.
…or ½ of the North Pacific sink for the same time period (ie May
to August).
Coastal CO2: Relationship to temperature and chlorophyll
Productivity &
CO2 uptake
N limitation
offshore
Coastal CO2 Fluxes: Satellite requirements
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Chlorophyll and SST will enable significant progress via
multiple linear regression techniques.
Temporal resolution ~3 hours will enable (primitive) budgets
to be calculated: tracking of processes such as productivity
and subduction. Higher temporal resolution of course better.
This is a dynamic environment – any ability to ‘clear’ or alias
clouds will enhance badly-needed coverage.
Critical spatial scales ~1 to 10km.
Current and proposed observational programs will provide the
necessary in situ data for validation.
Characteristics of the California upwelling system
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In contrast to Oregon, not a strong source or sink.
Possible reasons (ie differences from Oregon)
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Limitation of CO2 drawdown by something other than NO3
Greater warming (works against biological uptake)
Evidence for a significant change, towards a source, circa 1998
Illustrates the level of (lack of) understanding of the spatial and
temporal variability.
Coastal CO2: Relationship to physics and biology
Productivity &
CO2 uptake
N limitation
offshore
Coastal CO2: Relationship to temperature and particulate carbon