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Characteristics of eddies in the Gulf of Alaska are assessed from January 2003 through April 2012. Ensemble statistics for eddy subsurface water properties on isopycnals are computed using temperature and salinity profiles from Argo profiling floats located within eddies, which are identified in sea-surface height using objective techniques. Ninety cyclonic and 154 anticyclonic eddies are identified during this period. The anticyclonic eddies are strongly nonlinear and exhibit significant warm subsurface temperature anomalies and associated salty anomalies on isopycnals while no clear distinguishing subsurface anomalies on isopycnals are detected in association with the cyclonic eddies. Heat and freshwater fluxes for the eddies are estimated from integrations in depth coordinates. The anticyclonic eddies transport heat both westward off the continental shelf into the Subarctic Gyre and westward within the Alaskan Stream. However, they transport salt into the Subarctic Gyre and freshwater within the Alaskan Stream. In both pathways eddy heat and freshwater transport show possible year-to-year fluctuations, varying from 0 to 50.4 × 1018 J a−1 and −16.8 to +7.4 km3 a−1, respectively. The anticyclonic eddies are capped by relatively fresh water year-round.

Temperature and salinity both contribute to ocean density, including its seasonal cycle and spatial patterns in the mixed layer. Temperature and salinity profiles from the Argo Program allow construction and analysis of a global, monthly, mixed layer climatology. Temperature changes dominate the seasonal cycle of mixed layer density in most regions, but salinity changes are dominant in the tropical warm pools, Arctic, and Antarctic. Under the Intertropical Convergence Zone, temperature and salinity work in concert to increase seasonal stratification, but the seasonal density changes there are weak because the temperature and salinity changes are small. In the eastern subtropics, seasonal salinity changes partly compensate those in temperature and reduce seasonal mixed layer density changes. Besides a hemispheric seasonal reversal, the times of maximum and minimum mixed layer density exhibit regional variations. For instance, the equatorial region is more closely aligned with Southern Hemisphere timing, and much of the North Indian Ocean has a minimum density in May and June. Outside of the tropics, the maximum mixed layer density occurs later in the winter toward the poles, and the minimum earlier in the summer. Finally, at the times of maximum mixed layer density, some of the ocean has horizontal temperature and salinity gradients that work against each other to reduce the horizontal density gradient. However, on the equatorial sides of the subtropical salinity maxima, temperature and salinity gradients reinforce each other, increasing the density gradients there. Density gradients are generally stronger where either salinity or temperature gradients are dominant influences.