Impact of temperature dependent remineralisation on the global carbon cycle – Niels Bohr Institute - University of Copenhagen

Niels Bohr Institute > Calendar > 2012 > Impact of temperature ...

Impact of temperature dependent remineralisation on the global carbon cycle

Talk by J. Segschneider and J. Bendtsen, Centre for Ice and Climate

The impact of temperature dependent remineralisation of organic matter on the global carbon cycle is investigated by perturbing remineralisation rates in a global carbon cycle model with a Q10 of 2 and temperature anomalies for the late 21st century obtained from a CMIP5 RCP8.5 simulation with the MPI-ESM-LR. The initial response is an increase in remineralisation, that leads initially to a reduction of export production and in response to increased availability of nutrients in the euphotic layer. This leads to an increase in primary production which results, as opal is remineralized at greater depth than particulate organic carbon, to a depletion of silicate in the surface layer. In response, diatoms find less favourable growing conditions, and the export production of calcite forming organisms increases. This causes a decrease in alkalinity, and a resulting increase in pCO2 and thus outgassing of CO2. Over the 100 years of the model experiment, the ocean looses around 30 GtC of carbon, and most of this loss occurs as a secondary effect driven by the alkalinity change. In summary, the results indicate a small additional reduction of the oceanic uptake of anthropogenic CO2 from temperature dependent remineralisation that has not yet been included in future climate projections.