These hypotheses will be demonstrated below. In the Southern Ocean, CM5_piStart PLX4032 research buy is generally too cold around 50°S and too warm south of 60°S in the surface as compared to observations (Fig. 8 top left). The warm surface anomalies do not extend at depth though, where CM5_piStart is generally too cold over

the whole water column (Fig. 9 top left). This surface warm bias remains relatively unchanged in CM5_RETRO. Yet it extends down to almost 1000 m as well as along the oceanic floor (except for weak anomalies of the opposite sign between 50 m and 100 m, suggesting a modification of the thermocline). This is consistent with the forced simulations (compare F5_CMIP5 and F1_CMIP3, Fig. 2). The suite of sensitivity experiments in forced mode suggests that this effect is due to the implementation of the partial steps (F2). Bottom waters along the Antarctic continental shelf are colder in CM5_piStart as compared to CM5_RETRO. This is indicative of an intensified AABW formation, in agreement with forced

simulations, and confirmed by deeper mixed layers (not shown) and meridional streamfunctions (below). Furthermore, along the Antarctic continent, surface water masses are saltier Pexidartinib solubility dmso in CM5_piStart, while they are fresher north of 50°S (Fig. 9 bottom right). Fig 10 shows that these salinity anomalies in the Southern Hemisphere are responsible for an increase of the density gradient across Low-density-lipoprotein receptor kinase the Southern Ocean (80°S–50°S) in CM5_piStart by roughly 15% as compared to CM5_RETRO. This consistent with intensified ACC in CM5_piStart, as described below. Regarding the tropical regions, Fig. 8 (bottom) shows that surface waters are colder by up to 1 °C and saltier by more than 1.5 psu in CM5_piStart as compared to CM5_RETRO in the southern part of the Indonesian Archipelago

(IA). This results from the implementation of tidal mixing, consistent with coupled simulations from Koch-Larrouy et al. (2009). Further north, offshore of southeastern Asia, CM5_piStart displays a strong fresh anomaly compared to observations while this anomaly was much weaker in CM5_RETRO. This difference between the two simulations can be partly tracked down to changes in atmospheric freshwater flux, as shown in Fig. 12, with larger precipitation into the ocean (blue colour) in CM5_piStart along 5°N and weaker along the Equator and 5°S in the Indian Ocean. These changes are the signature of a northward shift of the ITCZ, and induce the SSS anomalies seen in Fig. 8 (bottom right). Note that from Fig. 12, atmospheric freshwater changes are also very strong in the tropical Atlantic, similarly characterised by a northward shift of the mean ITCZ position (around 10°N). Stronger precipitation are also found along 10°S.