Sensitivity Analysis and Parameter Tuning Scheme for Global Sea-Ice Modeling

• Main Authors: Jong G. Kim A, Elizabeth C. Hunke B, William H. Lipscomb B
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Key words; sea-ice model; automatic differentiation; parameter sensitivity; ice thickness; thermodynamics; dynamics; Arctic; Antarctic; Weddell Sea; Weddell; Antarc*; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.379.5538; http://info.mcs.anl.gov/pub/tech_reports/reports/P1282.pdf

Automatic differentiation (AD) is used to perform a multiple parameter sensitivity analysis for the Los Alamos sea-ice model CICE. Numerical experiments are run by six-hourly, 1997 forcing data with a two-hour time step, and the AD-based sensitivity scheme is validated by comparison with derivatives calculated using the conventional finite-difference approach. Twenty-two thermodynamic and dynamic parameters are selected for simultaneous analysis. Of these, the most important for controlling the simulated average sea-ice thickness is ice density; albedos and emissivity predominate in summer, while ice thickness is most sensitive to the ice conductivity in winter. The ice-ocean drag parameter and maximum ice salinity significantly affect the simulation year-round. Gradient information computed by the AD-based sea-ice code is then used in an experiment designed to assess the efficacy of this technique for tuning the parameters against observational data. Preliminary results, obtained with a bound-constrained minimization method and with simulated observational data, show that satisfactory convergence is obtained.