Trends in Terrestrial Trends in Terrestrial Carbon Sinks Driven by Carbon Sinks Driven by Hydroclimatic Change Hydroclimatic Change since 1948: Data-Driven since 1948: Data-Driven Analysis using FLUXNET Analysis using FLUXNET Christopher Schwalm, Christopher Williams, Kevin Schaefer, Kusum Naithani, Jingfeng Xiao Ameriflux Science Meeting & 3rd NACP All-Investigators Meeting 2011 January 31 – February 4, New Orleans, LA
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Trends in Terrestrial Carbon Sinks Trends in Terrestrial Carbon Sinks Driven by Hydroclimatic Change Driven by Hydroclimatic Change since 1948: Data-Driven Analysis since 1948: Data-Driven Analysis
using FLUXNETusing FLUXNET
Christopher Schwalm, Christopher Williams, Kevin Schaefer, Kusum Naithani, Jingfeng Xiao
• We ask– What are the carbon consequences of hydrologic
change?• We merge
– Global monitoring network (FLUXNET)– LUH time-varying land cover (IPCC AR5)– NCEP/NCAR Reanalysis
• We derive– Monthly time series (1948 – 2009)– 1° latitude/longitude resolution– Observationally-based estimates of carbon flux solely
attributable to hydrologic change
Outline
Global monitoring network
FLUXNET: Network of regional networksEddy covariance method: temporally dense in situ CO2 exchange including gross primary production and ecosystem respirationAncillary data: soil moisture, temperature, latent heat flux, LAI, etc.
Mapping points to pixels
Evaporative Fraction
Carb
on F
lux
Extract relationship between hydrologic change and carbon flux
Aggregate FLUXNET sites by IGBP land cover class
Calculate sensitivity: change in carbon flux to a unit forcing in evaporative fraction (z-score)
Sensitivity: g C m-2 month-1 σ-1
Map sensitivities to globe using
1) LUH [gridded land cover class]
2) NCEP/NCAR Reanalysis [gridded EF]
Schwalm et al. (2010) Global Change Biology
22 monm
Cg
monm
Cg
Spatial scaling: LUH land cover
1948
2009
62 annual snapshots of land cover from Land Use Harmonization (LUH)
Crosswalk: LUH → IGBP
http://luh.unh.edu/
IGBP maps18 IGBP land cover classes by pixel
FLUXNET sensitivitiesVegetated classes – observedNon-vegetated classes – set to zero