9531880 Davis In conjunction with a companion project by Dr. Brechner Owens of the Woods Hole Oceanographic Institution, 150 profiling ALACE (Autonomous Lagrangian And Circulation Explorer) floats will measure the absolute velocity and evolution of the temperature and salinity structure of the upper 1500 m in the subpolar gyre as part of the Atlantic Circulation and Climate Experiment (ACCE). Absolute velocities will be mapped at nominal depths of 400 and 1500 meters' depth using float arrays deployed uniformly over the basin. The velocity data will address three major pathways of the meridional overturning circulation (MOC) within the subpolar gyre: the shallow inflow of water into the regions of water mass modification; the convection that forms new dense waters; and the outflow of the resultant intermediate water from this source region. Temperature and salinity profiling will describe time evolution of the upper 1500 m, allowing quantification of the rates of water-mass modification in the warm-water limb of the MOC that supplies water for formation of deep and intermediate water. With 150 profiles observed roughly every ten days over two years, these observations will describe evolution with a combined temporal and spatial resolution greater than can be provided by all the other ACCE observations, especially over the winter-time convection season when other observations are extremely scarce. Analysis of these data will provide time series of three-dimensional maps of the velocity, temperature, and salinity fields within the upper 1500 m of the subpolar gyre over the duration of the ACCE field experiment. Additionally, statistical analyses will provide spatial distributions of mean circulation and quantities like eddy kinetic and potential energies, eddy mixing, and fluxes of heat and freshwater. These gyre-wide estimates will provide strong constraints for the future climate models that must be developed to adequately include the physics of the subpolar gyre, particularly convection. The absolute velocity measurements will also be used to reference large-scale geostrophic shears obtained from hydrography in this region where strong barotropic components are common.
