ABRUPT CHANGES IN ICE SHELVES AND ICE STREAMS: MODEL STUDIES

Open Access
Author:
Dupont, Todd K
Graduate Program:
Geosciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
November 24, 2003
Committee Members:
  • Richard B Alley, Committee Chair
  • Derek Elsworth, Committee Member
  • Raymond Gabriel Najjar Jr., Committee Member
  • James Kasting, Committee Member
Keywords:
  • ice shelf
  • ice stream
  • abrupt change
  • sea level
  • theoretical glaciology
Abstract:
Ice sheets are among the most important components of the Earth system because of their ability to force changes in climate and sea level. Ice streams are efficient pathways of mass flux from the interior of ice sheets. Thus an understanding of ice-stream dynamics is integral to an understanding of ice sheets and their interplay with the sea level and climate. Here a non-dimensional, 1-d model of the coupled mass and momentum balance of ice streams and shelves is developed. Longitudinal deviatoric stress is included in the force-balance component model. The mass-balance component model is time-dependent and thus allows simulation of the dynamic consequences of changes in boundary conditions or parameters. The model is applied to two problems. In the first study we address the sensitivity of ice-stream/ice-shelf systems to changes in ice-shelf buttressing. We find that for reasonable parameter values such systems are markedly sensitive to a loss of buttressing. Response include net grounding-line retreat on the order of 10\% of the length scale for the system and a roughly 30\% loss in the volume of ice above flotation. In the second study we examine the conditions under which ice flowing over a sill will tend to create a reversed ice/air surface slope. Here we find that such slope reversals occur within the range of reasonable parameter values, and thus should be expected, hence, ice shelf grounding on a sill can trap water driving subsequent thickening, eventually tending toward outburst flooding.