Heterogeneity of impacts of high CO2 on the North Western European Shelf

[摘要] The increase in atmospheric CO₂ is a dual threat to the marineenvironment: from one side it drives climate change, leading to modificationsin water temperature, circulation patterns and stratification intensity; onthe other side it causes a decrease in marine pH (ocean acidification, or OA)due to the increase in dissolved CO₂. Assessing the combined impact ofclimate change and OA on marine ecosystems is a challenging task. Theresponse of the ecosystem to a single driver can be highly variable andremains still uncertain; additionally the interaction between these can beeither synergistic or antagonistic. In this work we use the coupledoceanographic–ecosystem model POLCOMS-ERSEM driven by climate forcing tostudy the interaction between climate change and OA. We focus in particularon carbonate chemistry, primary and secondary production. The model has beenrun in three different configurations in order to assess separately theimpacts of climate change on net primary production and of OA on thecarbonate chemistry, which have been strongly supported by scientificliterature, from the impact of biological feedbacks of OA on the ecosystem,whose uncertainty still has to be well constrained. The global mean of theprojected decrease of pH at the end of the century is about 0.27 pH units,but the model shows significant interaction among the drivers and highvariability in the temporal and spatial response. As a result of this highvariability, critical tipping point can be locally and/or temporally reached:e.g. undersaturation with respect to aragonite is projected to occur in thedeeper part of the central North Sea during summer. Impacts of climate changeand of OA on primary and secondary production may have similar magnitude,compensating in some area and exacerbating in others.

[学科分类] 地球化学与岩石