Capturing the Complexity of Sea Ice and Salt-Water Interactions in Large-Scale Models
Recent years have seen rapid changes in the Arctic, including a rapid decline of summer sea ice. It is crucial for models to be able to capture these changes, including seasonal growth and melting of sea ice. These processes include complex interactions between sea ice and salty ocean water and ocean biogeochemistry. When sea ice first freezes, it incorporates salty ocean water into microscopic brine inclusions. Over time, this brine drains out in a process known as gravity drainage, resulting in a desalination of the sea ice. This drainage, in turn, sets up a circulating flow of brine with the ocean that provides an important nutrient source for organisms living in the brine inclusions. U.S. Department of Energy-funded researchers at Los Alamos National Laboratory (LANL) have developed a new thermodynamic module for the LANL sea-ice model, CICE, which simultaneously determines both the time varying temperature and sea-ice salinity. This new module improves on the previous version of CICE, which had a fixed salinity profile. Observational data from both tank experiments and fieldwork are used to guide and test the development of a simple gravity drainage scheme suitable for inclusion in a global climate model. The researchers have found that gravity drainage consists of two modes: rapid desalination near the base of the ice, and slower desalination throughout the ice. The model results compare well with both the experimental and fieldwork data.
Turner, A. K., E. C. Hunke, and C. M. Bitz. 2013. “Two Modes of Sea-Ice Gravity Drainage: A Parameterization for Large-Scale Modeling,” Journal of Geophysical Research Oceans, doi:10.1002/jgrc.20171.