Cause of Glacial Earthquakes in Greenland Clarified

ScienceDaily (Jan. 2, 2009) — Satellite observations during the past decade have shown dramatic changes in flow speed on year-to-year timescales at Greenland's outlet glaciers.

Seismic events traced back to glaciers during the same time period have been interpreted to have resulted from calving events at the glacier terminus or surging events lubricated by subglacial meltwater.

To learn more, Nettles et al. conducted geodetic studies at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer 2007. They observed several large and sudden increases in flow speed along the length of the glacier. These accelerations coincided with glacial earthquakes and major iceberg calving events.

No offset in the position of the glacier surface was observed during these events. Instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving as the generator of seismic events, putting to rest the idea that lurching glaciers are responsible for glacial earthquakes at outlet glaciers like Helheim, and demonstrating a link between ice loss and glacier acceleration.

Journal reference:

1. M. Nettles et al. Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland. Geophysical Research Letters, DOI: 10.1029/2008GL036127