However, during the following decades, the surface cooling progressively intensifies in our simulation to largely overwhelm the summer local warming, thus imprinting the annual mean response on the long BKM120 term. The inclusion of the biogeochemical component thus generally acts to cool the upper ocean up to 300 m depth. This response is rather large and dominates the
hydrographical differences between CM4_piCtrl and CM5_piCtrl. This is due to the specific profile of the chlorophyll in IPSL-CM5A, which translates substantial differences in nutrient distribution, incoming shortwave or ocean circulation as compared to IPSL-CM4. However, further work is needed to single out what prominent drivers are behind this change in the vertical profile of chlorophyll. Finally, two simulations integrated in parallel using rigorously the same atmospheric component and ocean initial conditions but oceanic models corresponding to the control version IPSL-CM5A and IPSL-CM4 respectively (thus differing by all aspects discussed PARP inhibitor above), named CM5_piStart and CM5_RETRO, were analysed. The sign of surface temperature
anomalies between CM5_piStart and CM5_RETRO is consistent with the effects of the biological module. Nevertheless, the amplitude of the differences in SST between CM5_piStart and CM5_RETRO are much larger than between CM5_piCtrl and CM5_piCtrl_noBio. Dynamical adjustments induced by additional parameterisations in the oceanic model indeed led to major improvements in particular in the representation of the Southern Ocean both thermodynamically (meridional density gradient) and dynamically (water mass transport). In particular, these
changes have enabled a strengthening of the barotropic flow of water mass of the Antarctic circumpolar current by about 20% and of the northward flow of Antarctic bottom water by about 17%. Below the surface, the amplitude of the differences between CM5_piCtrl and CM5_piCtrl_noBio is similar to the differences between CM5_piStart and CM5_RETRO, suggesting a leading role of the interactive biogeochemical module. Despite a stronger mass transport, the zonal ocean heat transport not in the Southern Ocean is even more underestimated in CM5_piStart than in CM5_RETRO as compared to a global inverse model based on observations (0.8 PW in Talley, 2003). This could partly come from an unrealistic southward heat transport in the South Atlantic in the former version, as well as from the thermal structure in the Southern Ocean. Indeed, most improvements in this region described above were shown to be dominated by salinity. In general, both heat and freshwater transport changes were found to be consistent with atmospheric fluxes and dynamic adjustments, and helpful in interpreting the latter.