• Energy Research

Based on the model of Paillard and Parrenin (2004), several box models that incorporate simple parameterizations of the oceanic CO2 pump were developed. The models’ parameters are calibrated to the δ18O and CO2 observational time series available for the last 800 kyr BP. The Paillard model performance may be improved if its CO2 sensitivity to insolation is eliminated and different response times are assumed both for absorption/emission of CO2 and for ablation/accumulation of ice. With these changes the correlations between simulated and experimental time series increase from 0.59 and 0.63 (for CO2 and ice volume V) to 0.77 and 0.88 respectively. Oceanic CO2 pulses of 10 to 20 kyr are found to take place at the beginning of the last nine deglaciations according to this model. The timing of the last nine terminations may also be qualitatively reproduced with a primary production model in which export depends on V. The dependence between CO2 export and V that generates the best fit is not exponential, as expected from some evidences, but a square function. The good model-data fitting suggests that the rate of formation of deep water may be an important factor controlling the oceanic pulse that triggers the deglaciations.

25 pages, 26 figures, 1 table, supplementary material https://doi.org/10.1007/s00382-012-1614-7 The model of Paillard and Parrenin (Earth Planet Sci Lett 227:263–271, 2004) was modified to obtain a closer fit to d18O and CO2 time series for the last 800 kyr. The model performance can be improved if its CO2 sensitivity to I65 insolation is eliminated and if different response times are assumed for ablation/accumulation of ice. Correlations between simulated and experimental time series for CO2 and ice volume V increase from 0.59 and 0.63 to 0.79 and 0.88, respectively. According to these models, terminations are produced by I65 amplification through CO2-T and T-CO2 feedbacks, in synergy with an extra CO2 contribution from the deep ocean. This contribution is strongly dependent on ice-sheet extent and ice volume (or alternatively, CO2 concentration, which is a good proxy of Antarctic temperature) but is insensitive to Southern Ocean (SO) insolation on 21 February (I60). Change of deep SO state may be the ‘‘order parameter’’ for nonlinear deglacial changes. According to these models, 100 kyr periodicity of glacial cycles arises from the characteristic time of Antarctic ice sheet advance to the continental slope This is a contribution to the TIC-MOC project funded by the 2008–2011 Spanish R + D Plan. [...] The work of one of the authors (C. Herrero) was supported by a CSIC JAE-Predoc scholarship co-financed by the European Social Fund (FSE) Peer Reviewed

16 pages, 7 figures, 1 table The model of Paillard and Parrenin (Earth Planet Sci Lett 227(3-4):263-271, 2004) has been recently optimized for the last eight glacial cycles, leading to two different relaxation models with model-data correlations between 0.8 and 0.9 (García-Olivares and Herrero (Clim Dyn 1-25, 2012b)). These two models are here used to predict the effect of an anthropogenic CO2 pulse on the evolution of atmospheric CO2, global ice volume and Antarctic ice cover during the next 300 kyr. The initial atmospheric CO2 condition is obtained after a critical data analysis that sets 1300 Gt as the most realistic carbon Ultimate Recoverable Resources (URR), with the help of a global compartmental model to determine the carbon transfer function to the atmosphere. The next 20 kyr will have an abnormally high greenhouse effect which, according to the CO2 values, will lengthen the present interglacial by some 25 to 33 kyr. This is because the perturbation of the current interglacial will lead to a delay in the future advance of the ice sheet on the Antarctic shelf, causing that the relative maximum of boreal insolation found 65 kyr after present (AP) will not affect the developing glaciation. Instead, it will be the following insolation peak, about 110 kyr AP, which will find an appropriate climatic state to trigger the next deglaciation. © 2013 Springer Science+Business Media Dordrecht This study has been carried out in the framework of project TIC-MOC (CTM2011-28867), funded by the 2008-2011 Spanish R+D Plan. C. Herrero acknowledges a CSIC JAE-Predoc scholarship co-financed by the European Social Fund (FSE) Peer Reviewed