Assessment of historical changes (1959–2012) and the causes of recent break-ups of the Petersen ice shelf, Nunavut, Canada

Aerial photography and satellite imagery of the Petersen ice shelf, Nunavut, Canada, from 1959 to 2012 show that it was stable until June 2005, after which a series of major calving events in the summers of 2005, 2008, 2011 and 2012 resulted in the loss of 61% of the June 2005 ice-shelf area. This recent series of calving events was initiated by the loss of extensive regions of >50-year-old multiyear landfast sea ice from the front of the ice shelf in summer 2005. Each subsequent calving event has been preceded by open-water conditions and resulting loss of pack-ice pressure across the front of the ice shelf, and most occurred during record warm summers. Ground-penetrating radar (GPR) ice thickness measurements and RADARSAT-2 derived observations of surface motion indicate that tributary glaciers provided total ice input of 1.19–5.65Mt a to the ice shelf from 2011 to 2012, far below the mean surface loss rate of 28.45Mt a. With recent losses due to calving and little evidence for current basal freeze-on, this suggests that the Petersen ice shelf will no longer exist by the 2040s, or sooner if further major calving events occur.