Bergen earth system model (BCM-C): model description and regional climate-carbon cycle feedbacks assessment

TitleBergen earth system model (BCM-C): model description and regional climate-carbon cycle feedbacks assessment
Publication TypeJournal Article
Year of Publication2010
AuthorsTjiputra, JM, Assmann, KM, Bentsen, M, Bethke, I, Otterå, OH, Sturm, C, Heinze, C
JournalGeoscientific Model Development
Start Page123-141
Date Published12/02/2010
PublisherCopernicus Publications on behalf of the European Geosciences Union

We developed a complex Earth system model by coupling terrestrial and oceanic carbon cycle components into the Bergen Climate Model. For this study, we have gene- rated two model simulations (one with climate change inclu- sions and the other without) to study the large scale climate and carbon cycle variability as well as its feedback for the period 1850–2100. The simulations are performed based on historical and future IPCC CO2 emission scenarios. Glob- ally, a pronounced positive climate-carbon cycle feedback is simulated by the terrestrial carbon cycle model, but smaller signals are shown by the oceanic counterpart. Over land, the regional climate-carbon cycle feedback is highlighted by increased soil respiration, which exceeds the enhanced pro- duction due to the atmospheric CO2 fertilization effect, in the equatorial and northern hemisphere mid-latitude regions. For the ocean, our analysis indicates that there are substan- tial temporal and spatial variations in climate impact on the air-sea CO2 fluxes. This implies feedback mechanisms act inhomogeneously in different ocean regions. In the North Atlantic subpolar gyre, the simulated future cooling of SST improves the CO2 gas solubility in seawater and, hence, re- duces the strength of positive climate carbon cycle feedback in this region. In most ocean regions, the changes in the Rev- elle factor is dominated by changes in surface pCO2, and not by the warming of SST. Therefore, the solubility-associated positive feedback is more prominent than the buffer capac- ity feedback. In our climate change simulation, the retreat of Southern Ocean sea ice due to melting allows an additional ∼20 Pg C uptake as compared to the simulation without cli- mate change.
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