Justin Burton from Emory University will be visiting to give the Department of Earth Sciences seminar on November 6 (Willamette 110, 4-5 pm). Justin does all kinds of neat research at the interface of granular materials and fluids. He will be talking to us about jamming in icebergs.
Accelerated warming in the past few decades has led to a dramatic increase in glacial activity. This is perhaps most apparent in tidewater glacial fjords, where gravitational flows from ice sheets are focused into narrow channels of thick, fast-flowing ice which terminate into the ocean. The result is a complex system involving both melting and iceberg calving (fracture) which has a direct impact on the Earth’s climate and sea level rise. However, there are numerous inherent difficulties in collecting field data from remote, ice-choked fjords. To address this, we use a laboratory scale model to measure aspects of tidewater glaciers which are not observable in nature. Our model has helped to uncover the source of glacial earthquakes, where floating, cubic kilometer scaled icebergs capsize due to gravitational instability, and temporarily reverse the velocity of the glacier. We have also investigated the granular nature of ice mélange, which is an enormous collection of broken icebergs and sea ice that sits in front of the largest glaciers in Greenland. The forces generated by the glacier slowly pushing the jammed mélange can be large enough to influence the calving of new icebergs, and the flow coherence of ice melange can be used as a predictor of impending calving events. This is perhaps the world’s largest granular material, and we have shown that the understanding of granular materials and rheology developed for laboratory-scale grains can also be applied here.