Analyzing the causes and spatial pattern of the European 2003 carbon flux anomaly in Europe using seven models

Abstract

Abstract. Globally, the year 2003 is associated with one of the largest atmospheric CO2 rises on record. In the same year, Europe experienced an anomalously strong flux of CO2 from the land to the atmosphere associated with an exceptionally dry and hot summer in Western and Central Europe. In this study we analyze the magnitude of this carbon flux anomaly and key driving ecosystem processes using simulations of seven terrestrial ecosystem models of different complexity and types (process-oriented and diagnostic). We address the following questions: (1) how large were deviations in the net European carbon flux in 2003 relative to a short-term baseline (1998–2002) and to longer-term variations in annual fluxes (1980 to 2005), (2) which regions exhibited the largest shift in carbon fluxes during the growing season 2003, and (3) which processes controlled the carbon balance anomaly . In Western and Central Europe, the anomaly in net ecosystem productivity (NEP) over growing season 2003 was outside the 1σ bound of the carbon flux anomalies for 1980–2005. The estimated growing season anomaly ranged between –29 and –196 Tg C for Western Europe and between 13 and –94 Tg C for Central Europe depending on the model used. All models responded to a dipole pattern of the climate anomaly in 2003. In Western and Central Europe NEP was reduced due to heat and drought. Over Western Russia NEP was decreased in response to lower than normal temperatures and high precipitation. While models agree on changes in simulated NEP and gross primary productivity anomalies in 2003 over Western and Central Europe, models diverge in the estimates of anomalies in ecosystem respiration. Except for two process models which simulate respiration increase, most models simulated a decrease in ecosystem respiration in 2003. The diagnostic models showed a weaker decrease in ecosystem respiration than the process-oriented models. Based on the multi-model simulations we estimated the total carbon flux anomaly over the 2003 growing season in Europe to range between –0.02 and –0.27 Pg C relative to the net flux in 1998–2002.

Uncertainties of modeling gross primary productivity over Europe: A systematic study on the effects of using different drivers and terrestrial biosphere models

“…The REMO simulations have a substantially higher spatial resolution (50 by 50 km) than the original T62 NCEP data (approximately 2°) and can be regarded as improved NCEP reanalysis. The REMO data set was chosen to drive all models because it extents until 2005; a prerequisite for a concomitant study on the 2003 heat wave [Vetter et al, 2007].…”

“…Investigating the model's sensitivity to 50% changes of WHC across 12 sites in Europe is the scope of active research. A detailed modeling protocol that contains information on regulations of model spin-up and transient runs as well as other input data which are kept fixed for all runs such as atmospheric CO 2 concentration, soil and elevation data sets is available in the work of Vetter et al [2007], and from the Web page (http://www.bgcjena.mpg.de/bgc-systems/projects/ce_i/index.shtml).…”

Competing roles of rising CO<sub>2</sub> and climate change in the contemporary European carbon balance

“…Here we build on the European biosphere simulations of Vetter et al (2007) and present results from simulations where we separate and quantify the competing effects of CO 2 and climate on contemporary European carbon balance.…”

Regional Meteorological–Marine Reanalyses and Climate Change Projections

“…For example, terrestrial biosphere models were driven with atmospheric input from coastDat to analyze gross primary productivity over Europe (Jung et al 2007) or to examine and assess the European 2003 carbon flux anomaly (Vetter et al 2008). …”