Calving of a large Greenlandic tidewater glacier has complex links to
meltwater plumes and mélange
Abstract
Calving and solid ice discharge into fjords account for approximately
half of the annual net ice loss from the Greenland Ice Sheet, but these
processes are rarely observed. To gain insights into the spatio-temporal
nature of calving, we use a terrestrial radar interferometer to derive a
three-week record of 8,026 calving events from Store Glacier, including
the transition between a mélange-filled and ice-free fjord. We show that
calving rates double across this transition and that the interferometer
record is in good agreement with volumetric estimates of calving losses
from contemporaneous UAV surveys. We report significant variations in
calving activity over time, which obfuscate any simple power-law
relationship. While there is a statistically significant relationship
between surface melt and the number of calving events, no such
relationship exists between surface melt and the volume of these events.
Similarly, we find a 70% increase in the number of calving events in
the presence of visible meltwater plumes, but only a 3% increase in
calving volumes. While calving losses appear to have no clear single
control, we find a bimodal distribution of iceberg sizes due to small
sections of ice breaking off the subaerial part of the front and large
capsizing icebergs forming by full-thickness failure. Whereas previous
work has hypothesised that tidewater glaciers can be grouped according
to whether they calve predominantly by the former or latter mechanism,
our observations indicate that calving here inherently comprises both,
and that the dominant process can change over relatively short periods.