Response of interdecadal tropical Atlantic SST variability to climate forcing during the last 21,000 years

The sea surface temperature (SST) anomalies over Northern and Southern subtropical Atlantic oceans are simultaneously fluctuating with opposite sign, which is called as the Atlantic meridional mode (hereafter, AMM). Since AMM can be amplified through the wind-evaporation-SST (WES) feedback, tropical Atlantic trade wind system including ITCZ and adjacent African and southern American monsoons are important factors to control AMM variation. In particular, the climate forcing change occurred during the last 21,000 years is expected to modify AMM. Here, we investigate the sensitivity of AMM to various climate forcing during the last 21,000 years using the transient simulations of CCSM3, so-called 'TraCE'. By analyzing not only a control simulation with all climate forcing but also the single-forcing simulations (e.g., Continental ice sheet topographic forcing, Melt Water flux forcing, and Orbital forcing), we found that the variability of AMM is strongly influenced by change in climate forcing, yet each climate forcing influences AMM differently. For example, the melt water pulse over north Atlantic results in the enhanced AMM variability through the increase of the WES feedback associated with the ITCZ migration. ITCZ migration is resulted from tropical Atlantic SST pattern change due to the weakening of Atlantic meridional overturning circulation. Detailed dynamics will be addressed further.