TY - JOUR
T1 - Temperature-dependent remineralization in a warming ocean increases surface pCO(2) through changes in marine ecosystem composition
AU - Segschneider, Joachim
AU - Bendtsen, Jørgen
PY - 2013/12/3
Y1 - 2013/12/3
N2 - Temperature-dependent remineralization of organic matter is, in general, not included in marine biogeochemistry models currently used for Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections. Associated feedbacks have therefore not been quantified. In this study we aim at investigating how temperature-dependent remineralization rates (Q10 = 2) in a warming ocean impact on the marine carbon cycle, and if this may weaken the oceanic sink for anthropogenic CO2. We perturb an Earth system model used for CMIP5 with temperature-dependent remineralization rates of organic matter using representative concentration pathway (RCP)8.5-derived temperature anomalies for 2100. The result is a modest change of organic carbon export but also derived effects associated with feedback processes between changed nutrient concentrations and ecosystem structure. As more nutrients are recycled in the euphotic layer, increased primary production causes a depletion of silicate in the surface layer as opal is exported to depth more efficiently than particulate organic carbon. Shifts in the ecosystem occur as diatoms find less favorable conditions. Export production of calcite shells increases causing a decrease in alkalinity and higher surface pCO2. With regard to future climate projections, the results indicate a reduction of oceanic uptake of anthropogenic CO2 of about 0.2 PgC yr-1 toward the end of the 21st century in addition to reductions caused by already identified climate-carbon cycle feedbacks. Similar shifts in the ecosystem as identified here, but driven by external forcing, have been proposed to drive glacial/interglacial changes in atmospheric pCO2. We propose a similar positive feedback between climate perturbations and the global carbon cycle but driven solely by internal biogeochemical processes. Key Points Temperature-dependent remineralization included in an Earth System Model Changes in marine ecosystem cause alkalinity-driven release of carbon Oceanic carbon sink additionally reduced by 0.2 GtC per year by 2100
AB - Temperature-dependent remineralization of organic matter is, in general, not included in marine biogeochemistry models currently used for Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections. Associated feedbacks have therefore not been quantified. In this study we aim at investigating how temperature-dependent remineralization rates (Q10 = 2) in a warming ocean impact on the marine carbon cycle, and if this may weaken the oceanic sink for anthropogenic CO2. We perturb an Earth system model used for CMIP5 with temperature-dependent remineralization rates of organic matter using representative concentration pathway (RCP)8.5-derived temperature anomalies for 2100. The result is a modest change of organic carbon export but also derived effects associated with feedback processes between changed nutrient concentrations and ecosystem structure. As more nutrients are recycled in the euphotic layer, increased primary production causes a depletion of silicate in the surface layer as opal is exported to depth more efficiently than particulate organic carbon. Shifts in the ecosystem occur as diatoms find less favorable conditions. Export production of calcite shells increases causing a decrease in alkalinity and higher surface pCO2. With regard to future climate projections, the results indicate a reduction of oceanic uptake of anthropogenic CO2 of about 0.2 PgC yr-1 toward the end of the 21st century in addition to reductions caused by already identified climate-carbon cycle feedbacks. Similar shifts in the ecosystem as identified here, but driven by external forcing, have been proposed to drive glacial/interglacial changes in atmospheric pCO2. We propose a similar positive feedback between climate perturbations and the global carbon cycle but driven solely by internal biogeochemical processes. Key Points Temperature-dependent remineralization included in an Earth System Model Changes in marine ecosystem cause alkalinity-driven release of carbon Oceanic carbon sink additionally reduced by 0.2 GtC per year by 2100
U2 - 10.1002/2013GB004684
DO - 10.1002/2013GB004684
M3 - Journal article
SN - 0886-6236
VL - 27
SP - 1214
EP - 1225
JO - Global Biogeochemical Cycles
JF - Global Biogeochemical Cycles
IS - 4
ER -
