USAP-DC

The Antarctic Circumpolar Current (ACC) is the strongest ocean current in the world, with a flow rate more than 100 times greater than all the rivers on Earth combined. This project continues a long-term study of ocean properties and variability in the ACC by repeat transects across the Drake Passage from Punta Arenas to Palmer Station using the USAP supply ship RV/AS LMGould. This project will provide information about long term trends and variability in Southern Ocean fronts, surface water mass properties, heat, and salinity budgets. This study will contribute to understanding the response of the ACC to atmospheric forcing on climate relevant time scales, and its role in driving the meridional overturning circulation of the Southern Ocean. These data represent the only year-round shipboard measurements in the Southern Ocean. This project will continue high-resolution, near-repeat XBT/XCTD/ADCP transect sampling in Drake Passage in order to study modes of variability in ocean temperature, salinity, currents and backscatter in the Antarctic Circumpolar Current (ACC). The data will capture variability on time scales from seasonal to interannual and on spatial scales from current cores to eddies. With almost two decades of data now available, the primary science objectives are to analyze the Drake Passage time series and (1) describe and relate the seasonal and long-term ocean energy distribution to wind, buoyancy and topographic forcing and sinks, and (2) describe and relate seasonal and long-term changes in the ACC fronts, water masses and upwelling to biogeochemical variability. The continued data collection, quality control and dissemination of the Drake Passage data sets to the broader oceanographic community are critical components of the project.