Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

Abstract

Abstract. Calving is a crucial process for the recently observed dynamic mass loss changes of the Greenland ice sheet. Despite its importance for global sea level change, major limitations in understanding the process of calving remain. This study presents high-resolution calving event data and statistics recorded with a terrestrial radar interferometer at the front of Eqip Sermia, a marine-terminating outlet glacier in Greenland. The derived digital elevation models with a spatial resolution of several metres recorded at 1 min intervals were processed to provide source areas and volumes of 906 individual calving events during a 6 d period. The calving front can be divided into sectors ending in shallow and deep water with different calving statistics and styles. For the shallow sector, characterized by an inclined and very high front, calving events are more frequent and larger than for the vertical ice cliff of the deep sector. We suggest that the calving volume deficiency of 90 % relative to the estimated ice flux in our observations of the deep sector is removed by oceanic melt, subaquatic calving, and small aerial calving events. Assuming a similar ice thickness for both sectors implies that subaqueous mass loss must be substantial for this sector with a contribution of up to 65 % to the frontal mass loss. The size distribution of the shallow sector is represented by a log-normal model, while for the deep sector the log-normal and power-law model fit well, but none of them are significantly better. Variations in calving activity and style between the sectors seem to be controlled by the bed topography and the front geometry. Within the short observation period no simple relationship between environmental forcings and calving frequency or event volume could be detected.

Automated detection and analysis of surface calving waves with a terrestrial radar interferometer at the front of Eqip Sermia, Greenland

“…Due to the distinctly different characteristics in ice cliff geometry and water depth, the calving front can be divided into sectors with shallow and deep water which exhibit different calving behaviour and event size statistics ( Fig. 1; Walter et al, 2020). The results in Figure 5d clearly show the difference between the deep and the shallow sectors in terms of number of waves and temporally cumulated WPI.…”

“…presented a novel method (TeRACWA) for the detection and the quantitative assessment of calving activity by analysis of calving waves recorded with a TRI. This method is complementary to other methods such as calving volume estimates by subtraction of Digital Elevation Models (DEMs) derived from drone imagery or from TRI interferometry(Walter et al, 2020; Temporally cumulated wave power index (orange bars; identical toFig. 5d) and fraction of meltwater plume occurrence (black line) along the calving front.…”

Thinning leads to calving-style changes at Bowdoin Glacier, Greenland

“…Observations show that for some tidewater glaciers, largescale infrequent calving events dominate the ice mass loss 486 E. C. H. van Dongen et al: Calving-style change Bowdoin Glacier over small frequent events (Walter et al, 2010;James et al, 2014;Åström et al, 2014;Medrzycka et al, 2016). We use the term "large-scale" relative to each individual glacier's annual mass loss through calving.…”

“…At Eqip Sermia (Greenland), inhomogeneous geometry causes different calving processes to occur; calving events are more frequent and larger where the fjord is shallow than for the deep part, which has a smaller ice cliff above sea level (Walter et al, 2020). When Columbia Glacier (Alaska) became ungrounded in 2007, a calving-style transition occurred from a steady release of low-volume icebergs to episodic flow-perpendicular rifting and release of very large icebergs (Walter et al, 2010).…”

Thinning leads to calving-style changes at Bowdoin Glacier, Greenland

“…Observations show that calving events can involve several processes both in time and space for a single glacier. At Eqip Sermia (Greenland), inhomogeneous geometry causes different calving processes to occur; calving events are more frequent and larger where the fjord is shallow than for the deep part which has a smaller ice cliff above sea level (Walter et al, 2020).…”