Effect of High-Frequency Deformation on Sea-Ice Thickness

Abstract

To fully describe sea ice as part of the climate system, it is necessary to account for processes on all temporal scales that contribute to changes to the ice thickness. Sea-ice thickness is determined both by thermodynamic and dynamic processes: the latter change the ice-thickness distribution and hence impact the ice-growth rate. Buoy data taken during winter show that a significant amount of sea-ice deformation occurs on a sub-daily scale generally associated with inertial motion. Here a thermodynamic model is forced with in situ measurements of sea-ice deformation to determine the importance of short-term dynamic processes on the ice-growth rate and annual ice production. The results of the thermodynamic model are verified with in situ ice-thickness observations; structural data from ice cores confirm the magnitude of dynamical enhancement of sea-ice thickness. Sensitivity tests show that from all input variables sea-ice growth strongly depends on air temperature. A single deformation event during the growth season can increase the thickness at the end of the model simulation by about 3 – 5%, with the initial increase (about 5 to 8 %) in ice thickness largely determined by the air temperature at the time of deformation. In a seasonal model run, with six deformation events, the resulting final ice thickness had increased by 12.5%. Due to the self-insulating effect of thick sea ice, ice growth caused by recurrent deformations does not scale linearly.