Carbon consequences of global hydrologic change, 1948-2009

Eddy covariance data (FLUXNET) provide key insights into how carbon and water fluxes covary with climate and ecosystem states. Here we merge FLUXNET data with reanalyzed evaporative fraction and dynamic land cover to create monthly global carbon flux anomalies attributable to hydrologic change from 1948 to 2009. Changes in land cover had a relative influence of <1% with an absolute effect less than uncertainty. The lack of trend globally in Net Ecosystem Productivity (NEP) attributable to hydroclimatic change masked positive trends in North America and Australia and negative trends in Africa and Asia. This spatial pattern coincided with geographic variation in hydroclimate excluding the temperature-limited high latitudes. Global NEP anomalies due to hydroclimatic variability ranged from -2.1 to +2.3 Pg C yr^-1 relative to a global average sink of +2.8 Pg C yr^-1. Trends in hydroclimate-induced NEP anomalies exceeded the background mean sink in many regions.