Calving and rifting on the McMurdo Ice Shelf, Antarctica

• Published in: Annals of Glaciology
• Main Authors: Alison F. Banwell, Ian C. Willis, Grant J. Macdonald, Becky Goodsell, David P. Mayer, Anthony Powell, Douglas R. Macayeal
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2017
• Subjects: Antarctic glaciology; iceberg calving; ice-shelf break-up; ice shelves; Meteorology. Climatology; QC851-999; Antarctic; McMurdo Ice Shelf; McMurdo Sound; Scott Base; Annals of Glaciology; Antarc*; Antarctica; Ice Shelf; Ice Shelves; Iceberg*; Sea ice
• Online Access: https://doi.org/10.1017/aog.2017.12; https://doaj.org/article/504432a5c88943a8ac32d826d6bbcf9a

On 2 March 2016, several small en échelon tabular icebergs calved from the seaward front of the McMurdo Ice Shelf, and a previously inactive rift widened and propagated by ~3 km, ~25% of its previous length, setting the stage for the future calving of a ~14 km2 iceberg. Within 24 h of these events, all remaining land-fast sea ice that had been stabilizing the ice shelf broke-up. The events were witnessed by time-lapse cameras at nearby Scott Base, and put into context using nearby seismic and automatic weather station data, satellite imagery and subsequent ground observation. Although the exact trigger of calving and rifting cannot be identified definitively, seismic records reveal superimposed sets of both long-period (>10 s) sea swell propagating into McMurdo Sound from storm sources beyond Antarctica, and high-energy, locally-sourced, short-period (<10 s) sea swell, in the 4 days before the fast ice break-up and associated ice-shelf calving and rifting. This suggests that sea swell should be studied further as a proximal cause of ice-shelf calving and rifting; if proven, it suggests that ice-shelf stability is tele-connected with far-field storm conditions at lower latitudes, adding a global dimension to the physics of ice-shelf break-up.