Implication of Plastic Sea Ice Rheology in Air-sea-ice Interactions
Jinro Ukita
International Arctic Research Center
The Frontier Research System for Earth Science
qpee@eorc.nasda.go.jp
Plastic rheology has been used over the last two decades to describe large scale material properties of sea ice. Numerical models based on this parameterization scheme capture basic geophysical features such as ice drift. Which suggests that this formation represents certain aspects of reality. Nevertheless, we lack understanding as to how in general this particular mechanical property of ice affects air-sea-ice interactions. Part of the problem is attributed to the fact that we do not have means to distinguish one rheology from others, except notions based on morphology.
In this talk, I first introduce a general definition for a class of non-Newtonian rheologies covering glacier and sea ice. On the basis of this definition, within the plastic framework distinctive roles of normal stress, shear stress, a principal direction of shear stress are examined. With this, we can interpret an observed deformation map over the Arctic.
In particular, it will be shown that plastic rheology admits to modify an ice velocity field from one under the free drift assumption. This gives rise to a memory effect. That is an interaction between past dynamic and themodynamic activities and present dynamic processes, especially in the area of thicker ice, i.e. off the Canadian Archipelago. It is also recognized that the structure of a horizontal ice boundary layer along with coastline depends upon rheology. This leads to the dependence of ice production and salt flux over the continental shelf region on mechanical property of ice such as viscous vs. plastic and/or linear vs. nonlinear rheology.
