NSIDC CPP Seminar: Iceberg Calving

The influence of granular ice mélange on iceberg calving by Ryan Cassotto, Post-doctoral Researcher at CIRES
Abstract: Ice mélange is an agglomeration of icebergs and sea ice found in many proglacial fjords. Ice mélange variations are hypothesized to trigger rapid tidewater glacier retreat; however, a lack of observations limits our understanding of ice mélange evolution. Deploying instruments on floating ice mélange is inherently dangerous and mélange turnover often exceeds temporal sampling by satellites. Consequently, studies have focused on wintertime conditions of quasi-ice shelf ice mélange and the interstitial sea ice that bolsters it, while few studies have investigated summer mélange conditions. Here, I provide an overview of winter ice mélange studies and then present the first known evidence of a late summer, granular ice mélange affecting iceberg calving in a Greenland fjord. We used high resolution terrestrial radar interferometry to monitor mélange speeds and strain rates before, during, and after calving. We find the granular ice mélange experienced increases in speed, a loss of coherent flow, and a breakdown in iceberg-iceberg contact prior to calving. Our results directly implicate granular ice mélange in the calving dynamics of tidewater glaciers and further demonstrates the potential for real-time detection of failure in geophysical granular materials.