Science Advances

Supplementary Materials

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  • Fig. S1. Air sampling sites for measurements of atmospheric CO2 mole fractions and δ13CO2 under NOAA’s Global Greenhouse Gas Reference Network between 2007 and 2015.
  • Fig. S2. Monthly and annual NEE used as prior fluxes in this study.
  • Fig. S3. Estimates of the North American land sink for 2000 to 2015 from published studies Butler et al. (19), Gourdji et al. (20), and Peylin et al. (18), and King et al. (17), recent releases of global inverse models (CAMS, Jena CarboScope, CT2016, and CTE2016), and from this study (CT-L).
  • Fig. S4. Multiyear average annual NEE (blue bars) and differences of NEE anomalies between El Niño and La Niña periods (red bars) between 2007 and 2015 for different ecoregions defined in fig. S1.
  • Fig. S5. IAV and ENSO response of North American NEE simulated by TBMs and atmosphere inverse models.
  • Fig. S6. Residuals between simulated and observed CO2 mole fractions.
  • Fig. S7. Vertical profiles indicating seasonally averaged residuals (differences) between simulated and observed CO2 mole fractions.
  • Fig. S8. Comparison of inversion results from OSSEs based on different model designs.
  • Fig. S9. Differences between posterior and true fluxes derived from observing system simulation experiments.
  • Fig. S10. Anomalies of NEE for North America derived from CarbonTracker (CT2016: black; CT2017: red).
  • Fig. S11. Correlation coefficients between NEE anomalies and anomalies of air temperature, precipitation, VPD, RH, and SM for spring (March to May), summer (June to August), fall (September to November), and winter (December to February) for major biome types over North America that have larger carbon uptake (indicated in fig. S4).
  • Fig. S12. Correlations between monthly NEE anomalies and monthly anomalies of hydrological variables (precipitation, relative humidity, vapor pressure deficit, and soil moisture) and the sensitivity of NEE anomalies to hydrological conditions.
  • Fig. S13. Correlations between NEE anomalies and anomalies of air temperature in spring and summer, and the sensitivity of NEE anomalies to air temperature.
  • Fig. S14. Difference of anomalies of air temperature, precipitation, relative humidity, vapor pressure deficit, and soil moisture between El Niño and non El Niño (neutral and La Niña) periods.
  • Fig. S15. Correlations between the ONI and 3-month average anomalies of area-weighted average precipitation, RH, SM, and VPD over boreal (blue symbols) and temperate (red symbols) North America with ±10-month time lags.
  • Fig. S16. Correlations between the ONI and 3-month average anomalies of area-weighted average precipitation, RH, SM, and VPD over temperate North America for every 20 years between 1950 and 2016.
  • Fig. S17. Atmospheric CO2 observations between 2007 and 2015 with different colors indicating their total sensitivity sumH, ppm (μmol m−2 s−1)−1 to North American land fluxes.
  • Fig. S18. Observed CO2 mole fractions for observations used in this analysis and their associated background estimates.
  • Table S1. Site information for CO2 mole fraction and δ13CO2 measurements made from NOAA flask air samples.
  • Table S2. Prior NEE, error covariance parameters, and background CO2 mole fractions used in the 18 inversion ensemble members in this study.
  • Table S3. Correlations between prior and posterior NEE anomalies over North America and anomalies of area-weighted average precipitation, RH, VPD, and SM over temperate North America.
  • Table S4. Correlations between the ONI and 3-month average anomalies of area-weighted average air temperature, precipitation, RH, VPD, and SM over boreal and temperate North America.

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