Iceberg Calving and Meltwater Drainage Observed in High Spatial and Temporal Resolution at Helheim Glacier, Greenland

Marine-terminating glaciers lose mass through calving and melting, and we find that meltwater drainage systems influence calving style and behavior at Helheim Glacier. We use high-resolution satellite and time-lapse imagery to observe variability in calving behavior, terminus position, supraglacial meltwater pooling, and surface expression of a buoyant meltwater plume at Helheims terminus from 2011-2019. Helheim, a tidewater glacier in East Greenland, maintained a relatively constant terminus position from 2011 through 2016 except for seasonal changes, but in 2017 and 2019 the terminus retreated ~1.5 km beyond previous positions. A supraglacial lake filled and drained in most summers, typically followed by down-glacier crevasse filling and buoyant plume appearance in a consistent location. All full-thickness calving events occurred either when this plume was not visible at the surface or were spatially removed from the surfacing plume. This is consistent with the hypothesis that the plume discharged from a well-established channelized drainage system, indicating a grounded glacial front. As the terminus became ungrounded, calving resumed and the plume disappeared. This relationship between meltwater drainage and calving behavior driven by subglacial hydrology likely exists at other lightly grounded outlet glaciers.