36-Year Surge Behaviors of the Sortebræ Glacier Complex in East Greenland, Revealed by Multisource Satellite Images

Abstract

Monitoring the behavior of surge-type glaciers is important for our understanding of glacier dynamics. However, in central East Greenland, one of the two clusters of surge-type glaciers in Greenland, only a few studies recorded the detailed surge characteristics, resulting in limited knowledge about the glacier's inherent surge cycle and the impact of climate change. In this study, we conducted a comparative study to explore the 36-year surge behavior of Sortebræ Glacier Complex (Sortebræ and Sortebræ West glaciers) in central East Greenland. Long-time-series ice velocity maps were produced by an image template matching method. For the first time, we revealed the surge dynamics of Sortebræ West in detail, which dominated three surges in 1986–1987, 1990–1991, and 2015–2016, reaching maximum ice velocities of 4307, 3135, and 8651 m a-1, respectively. During Sortebræ’s major surge in 1992–1995, we measured an ice velocity of 16 654 m a-1, which was twice the previous study's highest velocity. Combined with historical topographic maps and photographs, Sortebræ dominated two surge events, and its surge cycle was estimated at ∼40 years, whereas Sortebræ West experienced more frequent surge events (five times) in 1933–2021. Finally, we deduced that the surge characteristics of the Sortebræ Glacier Complex were consistent with the surge controlled by the subglacial drainage system. The surge system, however, may have changed because of the disengagement of two glaciers since 2015, caused by the uninterrupted retreat of the glacier terminus and the increased air temperature in recent years.