The "footloose" mechanism: Iceberg decay from hydrostatic stresses

Aerial view of PII-B-1 showing the approximate deployment locations of GPS stations
TitleThe "footloose" mechanism: Iceberg decay from hydrostatic stresses
Publication TypeJournal Article
Year of Publication2014
AuthorsWagner T.JW, Wadhams P., Bates R., Elosegui P., Stern A., Vella D., Abrahamsen E.P, Crawford A., Nicholls K.W
JournalGeophysical Research Letters
Volume41
Pagination5522-5529
Date Published2014/08
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000341725200027
Keywordsdrift; ice; iceberg beam theory; iceberg breakup observations; iceberg modeling; ocean
Abstract

We 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.

DOI10.1002/2014gl060832
Impact: 

We propose 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 over- burden from above an unsupported wavecut at the iceberg waterline created a submerged foot fringing the berg. We suggest that the buoyancy stresses within the berg induced by such a foot may be sufficient to cause moderate-sized bergs to break off from the main berg. A simple mathematical model is developed to test the feasibility of this mechanism. The model suggests that once the foot reaches a critical length, the induced stresses will be sufficient to cause breakup. The theoretically predicted maximum stable foot length is found to compare well to the data on breakup that was collected in situ. Further, the model provides analytical expressions for the ‘rampart-moat’ iceberg surface profiles that had been observed previously.

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