A Double Header

Séminaires de Edwin D. Waddington (University of Washington), mercredi 22 mai à 10h, salle Lliboutry, bât de Glaciologie

Analytical Depth-Age and Particle Paths in a Transient Dansgaard-Johnsen Model

Some glaciological questions are best addressed with numerical dynamical flow models that attempt to replicate all the physics, and consequently are expensive to run. Other questions are best addressed with simple kinematic models that can capture essential details and can be run many times at low cost. The steady-state Dansgaard-Johnsen (1969) model has been extended to generate 1-D analytical solutions incorporating transient ice-sheet thickness, surface mass balance, and basal melting.

New Perspectives on Polar Firn Compaction

Traditional firn-compaction models have been empirically calibrated against measured depth-density profiles, which are implicitly assumed to be in steady state. They often work remarkably well for many applications in the areas where they were calibrated. However, new questions related to bubble occlusion and to firn air content can be addressed by a next generation of models that are more directly physics-based, focusing on effective viscosity through evolution of firn micro-structural properties such as grain and bond sizes, coordination numbers, and structural anisotropy, among other properties. Micro-CT scanners are now collecting data that make this transition possible.

Edwin D. Waddington
Professor, Dept of Earth and Space Sciences
Box 351310 University of Washington
Seattle WA 98195-1310 USA

Séminaires animés par Frédéric Parrenin