The "footloose" mechanism: Iceberg decay from hydrostatic stresses

Abstract

8 pages, 4 figures, supporting information supplemental figures S1–S3 http://onlinelibrary.wiley.com/doi/10.1002/2014GL060832/suppinfoWe study a mechanism of iceberg breakup that may act together with the recognized melt and wave-induced decay processes. Our proposal is based on observations from a recent field experiment on a large ice island in Baffin Bay, East Canada. We observed that successive collapses of the overburden from above an unsupported wavecut at the iceberg waterline created a submerged foot fringing the berg. The buoyancy stresses induced by such a foot may be sufficient to cause moderate-sized bergs to break off from the main berg. A mathematical model is developed to test the feasibility of this mechanism. The results suggest that once the foot reaches a critical length, the induced stresses are sufficient to cause calving. The theoretically predicted maximum stable foot length compares well to the data collected in situ. Further, the model provides analytical expressions for the previously observed >rampart-moat> iceberg surface profiles. Key Points Observational iceberg data from 2012 Baffin Bay field experiment Mathematical model of iceberg decay due to hydrostatic stresses Analytic expressions for iceberg profiles and breakup conditions developed © 2014. American Geophysical Union. All Rights ReservedWe are grateful to the Office of Naval Research High Latitude Program for supporting the University of Cambridge participation through the MIZ-DRI project, grant N00014-12-1-0130. T.J.W.W. further acknowledges ONR grant N00014-13-1-0469Peer Reviewe