Datensatz

Zusammenfassung

The dynamics of the large outlet glaciers in Greenland is attracting both scientific and political attention due to the possible implications of a rising global sea level. Extensive glaciological and meteorological monitoring programmes have been implemented to quantify and track changes in the ice sheet and local glaciers (Ahlstrøm et al. 2008). The dynamic processes controlling the flow of the outlet glaciers are complex and poorly understood, involving a wealth of parameters such as bed conditions, hydrology and meteoro-logical conditions. It is desirable to obtain as many funda-mentally independent data sets as possible to understand and eventually predict the behaviour of the outlet glaciers. Some processes related to ice dynamics can be detected seismologically and thus completely independently from classical ice-monitoring techniques, such as satellite remote sensing, global positioning system (GPS) geodesy and auto-matic weather stations. Detectable cryo-seismological events include high-frequency ice quakes (Anandakrishnan & Bent-ley 1993; Harrison et al. 1993), calving events (O'Neel et al. 2006; Nettles et al. 2008) and less well understood processes such as low-frequency glacial earthquakes (Ekstrom et al. 2003; Nettles et al. 2008)) and glacial rumblings (Rial et al. 2009). Changes in ice load along the margin of the ice sheet can lead to earthquakes from glacial rebound, and earth-quakes can provide an independent constraint on ice mass redistribution (Johnston 1987; Stewart et al. 2000; Lund & Näslund 2009). The Greenland ice sheet monitoring network (GLISN) project will monitor changes in glacier dynamics using a large broadband seismological network. The network will also improve the detection of tectonic earthquakes in Green-land, thereby establishing a better baseline for local seismi-city. The baseline will allow detection of future changes in seismicity caused by changes in ice load. It is the objective of the project to contribute significantly to understanding the dynamics of the Greenland ice sheet and glaciers by studying cryo-seismological processes. Installing and operating a large real-time seismological network in Greenland is logistically complicated and expen-sive. An international team consisting of researchers from 10 institutions in 8 countries in Europe, North America and Asia are working together to meet this challenge (Fig. 1). Glacial earthquakes and rumblings Cryo-seismological events such as glacial earthquakes and rumblings can be linked to large-scale glacier dynamics. Gla-cial earthquakes are produced at large outlet glaciers and ap-pear to be associated with large calving events (Amundson et al. 2008; Nettles et al. 2008). However, the processes leading the GLISN group Fig. 1. Map of broadband seismographs in Greenland. 1–4: permanent stations operated by GEUS in cooperation with other institutions. 5–7: long-term stations maintained by GEUS. 8–9: new GLISN long-term stations run by ETH (Switzerland). 10: a long-term station run by GEO-FON (Germany). 11: a permanent station at Alert in Canada run by IRIS (USA). 12: a temporary station run by GEUS. 13–18: planned and funded new GLISN stations to be installed by IRIS and ETH.