Automated tracking of changes to terminus and mélange position in Greenland's marine outlet glaciers

Mass loss from the Greenland ice Sheet is primarily through the dynamic changes of its marine terminating outlet glaciers. Understanding the behavior of these glaciers is therefore key to understanding how much the ice sheet will contribute to sea level in the next century. Glacier behavior is, however, complex, with wide disparities in behavior even between glaciers that occupy adjacent fjords. Deciphering the multitude of factors that control glacier behavior requires a comprehensive dataset of near daily changes in terminus position for a large set of glaciers over many years. The creation of this dataset has been difficult due to the time required to process the changes manually. Evolution in computational methods allows the creation of an automated algorithm, using a combination of filtering techniques and edge detection, which ingests MODIS imagery and tracks changes to (i) the terminus position and (ii) the areal extent of melange downstream of the terminus. We tested the algorithm on several well-studied glaciers including Jakobshavn, Helheim, and Kangerdlugssuaq. Comparison with manually identified terminus positions proved the algorithm accurate to within +/- 2 pixels (500 m). The validated model was then applied to a larger set of Greenland's marine terminating outlet glaciers. We use this higher temporal resolution dataset to determine statistical patterns to the calving events and ask whether these patterns are linked to mélange extent, fjord geometry, and any seasonal component affecting the regularity of the events.