Published: April 17, 2014

Numerical experiments of dynamical processes during the 2011-2013 surge of the Bering-Bagley Glacier System, using a full-Stokes  finite element model

Thomas Trantow

Applied MathematicsUniversity of Colorado Boulder

Date and time: 

Thursday, April 17, 2014 - 10:00am

Location: 

ECAE 199

Abstract: 

The Bering-Bagley Glacial System (BBGS) is the largest ice system outside of the Greenland and Antarctic icesheets, and is Earth's largest surge-type glacier. Surging is one of three types of glacial acceleration and the least understood one. Understanding glacial acceleration is paramount when trying to explain ice discharge to the oceans and its glacial contribution to sea-level rise, yet there are currently no numerical glacial models that account for surging.

The recent 2011-2013 surge of the BBGS provides a rare opportunity to study the surge process through observations and the subsequent data analysis and numerical modeling. Using radar, altimeter, and image data collected from airborne and satellite missions, various descriptions of ice geometry are created at different times throughout the surge. Using geostatistical estimation techniques including variography and ordinary kriging, surface and bedrock Digital Elevation Maps (DEMs) are derived. A time series analysis of elevation change during the current surge is then conducted and validated using a complete error analysis along with airborne observations.

The derived DEMs are then used as inputs to a computer simulated model of glacier dynamics in the BBGS. Using the Finite Element software Elmer/Ice, a full-Stokes simulation, using Glen's flow law for temperate ice, is created for numerical experiments. With consideration of free surface evolution, glacial hydrology and surface mass balance, the model is able to predict a variety of field variables including velocity, stress, strain-rate, pressure and surface elevation change at any point forward in time. These outputs are compared and validated using observational data such as CryoSat-2 altimetry, airborne field data, imagery and previous detailed analysis of the BBGS.

Preliminary results reveal that certain surge phenomena such as surface elevation changes, surge progression and areas at which the surge start, can be recreated using the current model. Documentation of the effects that altering glaciological parameters and boundary conditions have on ice rheology in a large complex glacial system comes as secondary result. Simulations have yet to reveal any quasi-cyclic behavior or natural surge initiation.