According to this 2015 paper, we could predict the next calving event just by watching for melange movement on Sentinel, Modis, and Landsat pairs. Counter-intuitively, melange movement precedes
calving. Less glamorously, we could look backwards a few weeks and see if the current one could have been anticipated.
Seasonal and interannual variations in ice melange and its impact on terminus stability, Jakobshavn Isbræ, Greenland
R CASSOTTO, M FAHNESTOCK, JM AMUNDSON, M TRUFFER, I JOUGHINhttp://www.igsoc.org:8080/journal/61/225/j13j235.pdf
We used satellite-derived surface temperatures and time-lapse photography to infer temporal variations in the proglacial ice melange at Jakobshavn Isbræ, a large and rapidly retreating outlet glacier in Greenland.
Freezing of the melange-covered fjord surface during winter is indicated by a decrease in fjord surface temperatures and is associated with a decrease in ice melange mobility and a drastic reduction in iceberg production.
Vigorous calving resumes abruptly in spring following the steady up-fjord retreat of the sea-ice/ice-melange margin. An analysis of pixel displacement from time-lapse imagery demonstrates that melange motion increases prior to calving and subsequently decreases following several events.
... In the late 1990s the lower glacier began to thin due to intense submarine melting of a 10km long floating tongue . The resultant loss of buttressing forces caused the glacier to accelerate and stretch, causing the floating tongue to disintegrate and initiating a sustained retreat.
... There is a pattern of seasonal variation in terminus position superimposed on the long-term retreat that can be attributed to variations in the strength of the proglacial ice melange, a dense pack of icebergs that persists year-round, extends >15km down-fjord of the calving front, contains distinct shear bands and is densest near the terminus. Thus the ice melange may act like a weak, granular ice shelf that inhibits calving by transmitting stresses from the fjord walls to the glacier terminus.
... Seasonal variations in calving are important because they influence a glacier’s long-term rate of retreat
through nonlinear processes; longer warm periods that extend the calving season could lead to greater rates of retreat.
... We used MODIS sea surface temperatures (thermal infrared emission) to generate a 12-year proxy record of daily fjord ice conditions in Ilulissat Icefjord
... the 11 April 2009 calving event was the first event of that year; the onset of the break-up of the seasonal floating tongue show an increase in melange mobility in the days leading up to calving. A profile of speed shows the floating
tongue advected into the field of view on 22 March. The tongue progressed steadily down-fjord over the next 20 days. By 8 April, the melange in front of the tongue started to speed up, and on 11 April a large calving event caused the floating tongue to disintegrate and disappear from the profile.
... The speed of the melange increased >40% over mean winter values in the days leading up to calving. Following the event, speeds were much slower as the advancing glacier terminus pushed the post-calving melange down-fjord and compacted it.
... The ability of the melange to prevent ice at the terminus from overturning decreases as the mobility of the melange increases, leading to more frequent calving during periods of enhanced mobility.
... Our record of melange conditions demonstrates that winters with persistently low surface temperatures, taken to indicate rigid and immobile ice melange, had few calving events which permitted the glacier terminus to advance several
kilometers and form a floating tongue.
... Though an ice melange may not have sufficient strength to directly impact the glacier force balance, it can impact glacier velocities indirectly by regulating calving.
...The ability of melange to influence calving seems to have diminished in recent years as conditions warmed and the glacier has retreated into deeper water.