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Motion of ice sheets at their margins: Modeling studies

  • Author(s): Lindsey, Daniel Seneca
  • Advisor(s): Primeau, Francois
  • et al.
Creative Commons 'BY' version 4.0 license
Abstract

Ice sheets interact dynamically with the ocean, losing mass through ocean-induced melt and the calving of icebergs. At ice sheet margins, ice shelves buttress flow of tributary glaciers making them a critical component of the overall ice sheet stress balance and, consequently, mass budget. With retreat of ice shelves seen in both Antarctica and Greenland, accurate modeling of ice shelf motion is important for forecasting future sea-level rise. Presently, most glacier models leave the calving front fixed in time with the implicit assumption that flow at the calving front is balanced by calving resulting in a stationary front. Numerically evolving a calving front is challenging in two ways, the first is due to the difficulty in applying the correct calving front boundary condition as the front shifts in time and the second lies in utilizing an appropriate numerical treatment for the calving process. Many factors influence calving including ocean-induced melt, surface melt-water hydrofracturing of crevasses, and wave energy triggering calving events. Of importance at some Greenland glaciers, melange, a mixture of icebergs and sea ice, can act to suppress calving rates by either preventing calved bergs from rotating away from the front or directly buttressing front strain rates.

In this dissertation we utilize two mathematical techniques, the level-set method and diffuse-domain method, to develop an ice shelf model that allows for the temporal evolution of a calving front. Our ice-shelf model allows for mesh independent enforcement of the appropriate boundary condition thus allowing for continuous motion of the front within mesh elements. We validate this model in both a 1D domain and 2D idealized domain. We then apply these front-motion methods to the evolution of the Ross ice shelf and examine characteristics of flow through time. Our model captures key features of ice-shelf flow and produces a smooth evolution of the front. Finally, we use our ice shelf model to examine the potential for melange to buttress ice shelf calving front strain rates. We find that melange, if rheologically strong enough, of 100 m thickness shearing over 1 km can initiate a calving front advance of 490 m/a.

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