Controls on Helheim Glacier calving rates from 2001-2014

Tuesday, 16 December 2014
Leigh A Stearns1, Steven C Foga2, Gordon S Hamilton3, Fiammetta Straneo4, Dave Sutherland5, Cornelis J van der Veen2, Marilena Oltmanns4 and Kristin M Schild6, (1)University of Kansas, Department of Geology, Lawrence, KS, United States, (2)University of Kansas, Department of Geography, Lawrence, KS, United States, (3)University of Maine, Orono, ME, United States, (4)WHOI, Woods Hole, MA, United States, (5)University of Oregon, Eugene, OR, United States, (6)Dartmouth College, Hanover, NH, United States
Iceberg calving is an efficient mechanism for ice mass loss. While the physical controls on calving are not well understood, recent field and remote sensing observations from Helheim Glacier, southeast Greenland, suggest calving is dependent on both glacier and fjord conditions. This presentation investigates the sensitivity of calving rates to ice velocity, ocean temperature and mélange composition using a combination of in situ and satellite observations. Ocean properties in Sermilik Fjord for 2009-2014 are reconstructed using mooring data, and an object-based image analysis (OBIA) that inventories icebergs, sea-ice and small icebergs quantifies mélange composition several times a season. Ice velocity from InSAR and optical imagery is used to calculate calving rates and investigate the role of longitudinal gradients on calving.

Ice velocity appears to be the dominant control on calving rates at Helheim Glacier. However, calving rates exhibit a complex pattern of seasonal and interannual variability, which does not simply mimic ice velocity patterns. We explore the relative roles of ocean properties, glacier geometry, and mélange composition on calving rates from 2001–2014 in order to improve physically-based glacier models.