Surface Ventilation and Circulation

Abstract

There has been tremendous progress in the last decade in observing surface circulation and its variability, mainly resulting from the longer records and higher quality of various satellite and surface drifter data sets, along with new analysis methods. Observation of upper ocean subsurface circulation is necessarily lagging behind because in situ sampling cannot match the satellite coverage; progress is being made using Argo (Array for Real-time Geostrophic Oceanography) profiling, subsurface velocities (moorings and floats), and data assimilation. Western and eastern boundary regions have very different spatial and temporal sampling requirements from the interior circulation and from each other; few are fully instrumented for longterm monitoring, but these are producing climateappropriate records of velocity, temperature and transport. Coastal circulation is increasingly monitored by high frequency radars.Ventilation and upwelling processes connect the surface layer and underlying interior. Locally these processes are complex combinations of air-sea fluxes, convection, stratification/restratification, and frontal processes, down to the submesoscale (1 to 10 km). Ongoing research ship observations provide quantitative information on formation rates and residence times, and compelling evidence of decadal ventilation changes. The Argo profiler network is beginning to produce time series that show interannual variations in major water masses.Combination of improving air-sea flux products and surface density distributions is yielding ever-improving quantitative estimates of formation rates and variability. Progress in understanding the many processes involved in ventilation has been made through regional experiments and high-resolution modeling of mixed layer and frontal processes.Recommendations for the next decade include: maintenance of relevant existing observing systems, continued improvement of air-sea flux products, continued improvement of synthesis methods, implementation of the satellite SWOT (Surface Water Ocean Topography) and surface salinity missions, expansion of autonomous subsurface profiling to include oxygen and turbulence profiling, and implementation of local observing systems in strategic locations in boundary currents and dense water formation sites.

Ocean Reference Stations

“…Like global weather maps of wind, barometric pressure, and atmospheric humidity and temperature properties, global maps of the ocean circulation, sea level, and temperature and salinity properties are needed to visualize, quantify, and understand the ocean physical variability (Cazenave et al, 2010;Schmitt et al, 2010;Talley et al, 2010;Wijffels et al, 2010). For understanding and quantifying the ocean and atmosphere interactions, maps of the airsea fluxes of heat, moisture, momentum, and gasses are needed (Fairall et al, 2010;Gulev et al, 2010).…”