relationship between SSS and SST in the western Pacific and the barrier layer is instrumental in maintaining heat and momentum in the warm pool within the salinity stratified layer. Later work, including Argo drifters, confirm the relationship between eastward migration of the warm pool during El Nino and BLT heat storage in the western Pacific. The main impact of BLT is to maintain a shallow mixed layer allowing an enhanced air-sea coupled response. In addition, the BLT is the key factor in establishing the mean state that is perturbed during El Nino/La Nina References Oceanography