Granular particle dynamics:
Ice sheets and glaciers are usually viewed as continuous materials that behave like fluids over long time-scales and elastic solids over short time-scales. However, in addition to deforming ice also fractures. This is ultimately the reason why icebergs detach. As an alternative to the usual continuum description of glaciers, my group has started to develope models of glaciers in which the ice behaves more like a granular material. Below, you can see a movie in which the ice is imagined to consist of spherical “boulders” of ice that interact elastically and through friction. The ice is advancing into an over deepening trough. Note the isolated boulders that detach from the debris pile as it advances into deeper water. We believe that much of the behavior of rapidly flowing tidewater glaciers is better explained from a granular material point of view than a continuous point of view. For example, one of the most robust predictions of our model is that iceberg detach when the ice starts to approach buoyancy. This “height-above-buoyancy” calving behavior has been so ubiquitously observed that it has often been elavated to the status of “law”.
Bonded particle dynamics:
We can also “glue” particles together to simulate an elastic and allow bonds to fail in tension or shear to simulate fracture of a brittle elastic solid. The two animations shown below illustrate calving events simulated from a Helheim Glacier like glacial geometry. The animation on the left shows an iceberg that capsizes outward, as is often observed. The animation on the right shows an iceberg that is slightly too wide to capsize and instead drifts off where it becomes lodged against a protrusion in the embayment. Read more about this research here and here.