Atmospheric inversion of co2 sources and sinks Northern Hemisphere sink Jay S. Gregg

Atmospheric inversion of CO2 sources and sinks Northern Hemisphere sink

• Jay S. Gregg

Goal

• Inverse modeling identifies carbon sources and sinks, and coupled with a planetary transport model, generates predicted CO2 concentrations.

• Ideally, the model is adjusted so that the predicted flux measurements best match those measured at various locations around the globe.

Components

• Observed Atmospheric Concentrations of CO2

• Spatiotemporal concentrations (ppm) of CO2

• Observed Sea Surface Concentrations of CO2

• Partial Pressure of CO2

• General Circulation Model

Sources and Sinks Involved

• Fossil-Fuel-Based Emissions (Confidence: High)

• Land Use Change (Confidence: Low)

• Terrestrial Ecosystem Response to Elevated CO2 (Confidence: Low)

• Terrestrial Sink (Confidence: Low)

• Ocean Sink (Confidence: Low)

• *Confidence refers to amount, temporal pattern, and spatial location

Atmospheric CO2 Observations

• Geophysical Monitoring for Climate Change (GMCC) Network

• Based on flask measurements

• 20 cites since 1980

Atmospheric CO2 Sampling Sites

Atmospheric CO2 Concentration

Oceanic Observations

• Observed pCO2 difference between surface ocean and atmosphere

• Transect Sampling, some data gaps in Indian and Southern Ocean- extrapolation based on Sea Surface Temperatures

• Oceans divided into 2o x 2o grids, and mean pCO2 is calculated for the periods (January through April) and (July through October)

Oceanic CO2 Calculations

• Working Formula for F (CO2 flux across air-sea interface):

Oceanic CO2 Calculations

Oceanic CO2 Fluxes

Oceanic CO2 Fluxes

Transport Model

• 3-D General Circulation Model (GCM) from Goddard Space Flight Center, NASA

• Seasonal, diurnal

Transport Model (vs. Observed)

Modeled Atmospheric CO2 Concentrations

Modeled Fluxes

Modeled Fluxes

Modeled NPP

Modeled CO2 Sources and Sinks

• Atmospheric CO2 increases about 3 Gt C/yr

• Sinks are larger in northern hemisphere than southern

• ocean sink is largest at equator
• must be a larger northern terrestrial sink

• El Nino and La Nina cycles changes fluxes

• Still a lot of uncertainty in global carbon cycle

Which Transport Model to Use?

• Many different transport models can give different results

• Underscores uncertainty in inverse model results

• Transcom 3 Project (Gurney, 2002) seeks to compare the outcome from various models

Which Transport Model to Use?

Which Transport Model to Use?

Factors in CO2 Flux Variability

• El Nino and La Nina (increased biomass burning), changes in NPP

• Volcanic Eruptions (e.g., Pinatubo- changes in NPP from sunlight limitations)

• Temperature and humidity affect microbial respiration (soil respiration increases at higher temperatures)

References

• I.G. Enting, C.M. Trudinger, R..J.A. Francey (1995) A synthesis inversion of the concentration of 13C of atmospheric CO2. Tellus B 47, 35-52.

• S. Fan, et al., (1998) A large terrestrial carbon sink in North America implied by atmospheric and oceanic carbon dioxide data and models. Science 282, 442-446.

• K. R. Gurney et al., Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models, Nature 415, 626 (2002).

• C. Roedenbeck, S. Houweling, M. Gloor, and M. Heimann (2003) CO2 flux history 1982–2001 inferred from atmospheric data using a global inversion of atmospheric transport, Atmos. Chem. Phys., 3, 1919–1964.

• P. P. Tans, I. Y. Fung, T. Takahashi, (1990) Observational Constraints on the Global Atmospheric CO2 Budget, Science 247, 1431-1438.