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Ice and Mud: How Sediment Dynamics Drive Periodicity in Tidewater Glaciers

Douglas Brinkerhoff, Department of Computer Science, University of Montana
Fri, February 23, 2018, 10:30am - 11:30am

Video Broadcast

Host: Ginny Catania

Many tidewater glaciers in Alaska, such as Hubbard, Taku, and Yahtse, are growing despite a warming atmosphere and ocean. At the same time, close neighbors such as Columbia glacier are undergoing dramatic retreats, which cannot be accounted for by climate change. What drives this apparent disparity in glacier behavior? A hypothesized process known as the tidewater glacier cycle provides an explanation: movement of sediment by sub glacial streams produces a shoal at the glacier front, decreasing the amount of iceberg calving and allowing the glacier to advance over several hundred years. Eventually the glacier becomes overextended, floats, and quickly retreats to its initial shape. In this talk, I will show (with the help of computer model) that simple interactions of ice, water, and erosion can produce tidewater glacier cycles like the ones that are observed in coastal Alaska, and that these cycles occur even in a static climate and persist with warming. I argue that these cycles drive natural shifts in marine habitat and the fjord landscape at large and must be accounted for in interpretations of glaciers as climate proxies.