Geocheminar spring-2013

Many of Greenland's largest glaciers produce seismic signals equivalent in amplitude to those from earthquakes of M ~ 5. The earthquakes show a strong seasonal signal, with most events occurring in late summer, as well as a secular variation, with 3-6 times as many earthquakes occurring in each recent year as in the early 1990s. Rapid changes in glacier flow speeds, thinning rates, and terminus positions have also been observed during the past decade, but remain poorly understood. These dynamic glacier processes account for approximately half of the ice-mass loss currently occurring in Greenland. We combine globally recorded seismic signals, space-based remote-sensing data, and local geodetic observations at large Greenland outlet glaciers to obtain insight into the glacial-earthquake source process and the response of outlet glaciers to changing environmental conditions, including ice loss at the glacier terminus and varying surface meltwater input. Systematic analysis of glacial earthquakes across Greenland shows that spatio-temporal trends in earthquake occurrence are closely linked to changes in ice dynamics, and allows us to use the earthquakes as a remote-sensing tool.