Image courtesy of Uwe Kils
Krill feed on algae living within sea ice brine in the Arctic. Researchers are working to improve how climate models represent the desalinization processes associated with such ice.
The Arctic has experienced rapid changes in recent years, including the fast decline of summer sea ice. Researchers at Los Alamos National Laboratory (LANL) have developed a new thermodynamic module for CICE, the LANL sea-ice model. This module simultaneously determines both the time-varying temperature and salinity of sea ice, improving on the previous version of CICE, which had a fixed salinity profile.
Accurate climate model representations of these changes, particularly the seasonal growth and melting of sea ice, are crucial for improving projections of climate effects on Arctic ecosystems.
Arctic freezing and melting processes involve complex interactions among sea ice, salty ocean water, and ocean biogeochemistry. When sea ice first freezes, it incorporates salty water from oceans into microscopic brine inclusions. Over time, this brine empties out in a process known as gravity drainage, resulting in desalination of the sea ice. This drainage in turn sets up a circulating flow of brine in oceans that becomes an important nutrient source for organisms living within the brine inclusions. Observational data from both tank experiments and fieldwork were used to guide and test the development of a simple gravity-drainage scheme suitable for inclusion in a global climate model. The researchers found that gravity drainage consists of two modes: a rapid desalination near the base of the ice and a slower desalination throughout the ice. Model results aligned well with both experimental and fieldwork data.
Adrian K. Turner
Los Alamos National Laboratory, MS B210
Los Alamos, NM 87545
A. Turner and E. Hunke are supported by the Earth System Modeling and Regional and Global Climate Modeling programs of the Office of Biological and Environmental Research within DOE’s Office of Science.
Turner, A.K., Hunke, E.C., and Bitz, C.M. “Two modes of sea-ice gravity drainage: A parameterization for large-scale modeling.” J. Geophys. Res. Oceans 88, 1–16 (2013). [DOI: 10.1002/jgrc.20171]
University, DOE Laboratory