Our current understanding of the dynamics governing Arctic upper ocean stratification and circulation largely derives from a period when extensive ice cover greatly modulated the oceanic response to atmospheric forcing and resulted in weak seasonality, at least within the deep basins. However, recent years have witnessed significant Arctic warming, accompanied by changes in the extent, thickness distribution and properties of the Arctic sea ice cover. Sea ice has become younger and thinner alongside the decreases in extent, pointing to a persistent loss of sea ice volume. Thinner, younger ice tends to be weaker, more subject to deformation and fracturing, and thus more mobile and more likely to provide efficient coupling between the atmosphere and upper ocean. Furthermore, the growing summertime expanses of open water provide periods when the dynamics might more closely resemble those that govern the upper ocean at lower latitudes. The need to understand these changes and their impact on Arctic stratification and circulation, sea ice evolution and the acoustic environment motivate the Office of Naval Research (ONR) Stratified Ocean Dynamics of the Arctic Departmental Research Initiative (SODA DRI).
The SODA team focused on understanding the processes that govern the exchange of heat, freshwater and momentum within the ocean-ice-atmosphere system, and how these vary over an annual cycle as a function of ice condition, atmospheric forcing and proximity to open water. The observational program included an intensive, summertime process study conducted from R/V Sikuliaq, glider-based sections, and year-long time series measurements collected from a mooring array with a 500-km latitudinal span, ice-based instrument clusters and profiling floats. The SODA field program also featured interagency participation, with contributions from the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), the National Science Foundation (NSF) and the Bureau of Ocean Energy Management (BOEM). This presentation will provide an overview of the SODA program and present early results from the measurement program, which concluded in autumn 2019.