Presented at the Global Ocean Salinity and the Water Cycle WorkshopA major goal as part of the SPURS-2 field campaign is to understand the characteristics and variability of the upper ocean salinity stratification in the vicinity of the ITCZ and identify the main mechanisms that are responsible for this variability. Our contribution focused on the âmesoscaleâ box (10-300 km) spatial scale, undertaking upper ocean stratification and velocity measurements that will help provide some regional context for the nested small-scale and single-point moored measurements. In all, we completed 50 CTD-O2/LADCP stations and 260 uCTD stations during the SPURS-2 cruise in August-September 2016. Salt-stratified barrier layers were observed during the cruise where the warm layer extends deeper than the fresh surface layer. Their formation mechanism in the eastern Pacific is not as yet clear but likely candidates include rainfall and advective processes (current shear and S-gradients). Other stratification profiles were characterized by very thick (>20 m) temperature inversions occurring at the base of the isohaline layer. These temperature-inversions appeared to be ubiquitous at the base of the fresh pools in the halocline, especially in the vicinity of strong fronts. It is as yet unknown if these are transient features or indeed what their time scales might be. Numerous mechanisms might be responsible for their formation including wind forced advection of cold water over warm water; net heat loss at the sea surface; advection of cold less saline water over warm saline water; fronts; and water mass interleaving.