Project

Discipline

Glacial Earthquakes; Greenland Ice Sheet; Global Warming; Seismology; Glaciology; Greenland

Lead
Lay summary
In this project we will install state-of-the art seismic stations in Greenland as a part of a new international broadband seismic capability for Greenland, the GreenLand Ice Sheet monitoring Network (GLISN)-a real-time sensor array that enhances and upgrades performance of the very-limited existing Greenland seismic infrastructure for detecting and characterizing glacial earthquakes and other phenomena emitting seismic waves. The Greenland Ice Sheet is changing, and seismology has the means to "hear" and measure these changes. Continuous, long-term monitoring of the dynamics of the Greenland Ice Sheet and its relationship to global climate change is a fundamental observational enterprise which requires multi-sensing techniques. The development of GLISN brings the seismology component into focus for monitoring Greenland's Ice Sheet.Glacial earthquakes have been observed along the edges of Greenland with strong seasonality and in-creasing frequency since 2002 by continuously monitoring data from the Global Seismographic Network (GSN). These glacial earthquakes in the magnitude range 4.6-5.1 may be modeled as a large glacial ice mass sliding down-hill several meters (e.g. 10 cubic-km by 10 m) on its basal surface over a duration of 30 to 60 seconds. Although the mechanics of sudden sliding motions at the glacial base are not known, seasonal and temporal patterns are consistent with a dynamic response to climate warming driven by an increase in surface melting and supply of meltwater to the glacial base, and suggest that the glacial earthquakes may serve as a marker of ice-sheet response to external forcing.The Swiss Seismological Service (SED), ETH Zurich, plans to participate in this international project by taking responsibility for 2-3 stations in the network in settlements on the west coast of Greenland

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

This proposal requests funding for a state-of-the art seismic station located on an icesheet in the Arctic. This station will be a component of a new international broadband seismic capability for Greenland, the GreenLand Ice Sheet monitoring Network (GLISN)-a real-time sensor array that enhances and upgrades performance of the very-limited existing Greenland seismic infrastructure for detecting and characterizing glacial earthquakes and other phenomena emitting seismic waves. The Greenland Ice Sheet is changing, and seismology has the means to “hear” and measure these changes. Continuous, long-term monitoring of the dynamics of the Greenland Ice Sheet and its relationship to global climate change is a fundamental observational enterprise which requires multi-sensing techniques. The de-velopment of GLISN brings the seismology component into focus for monitoring Greenland’s Ice Sheet.Glacial earthquakes have been observed along the edges of Greenland with strong seasonality and in-creasing frequency since 2002 by continuously monitoring data from the Global Seismographic Network (GSN). These glacial earthquakes in the magnitude range 4.6-5.1 may be modeled as a large glacial ice mass sliding down-hill several meters (e.g. 10 km3 by 10 m) on its basal surface over a duration of 30 to 60 seconds. Although the me-chanics of sudden sliding motions at the glacial base are not known, seasonal and temporal patterns are consistent with a dynamic response to climate warming driven by an increase in surface melting and supply of meltwater to the glacial base, and suggest that the glacial earthquakes may serve as a marker of ice-sheet response to external forcing.The detection and characterization of smaller glacial earthquakes are limited by the propagation distance to globally distributed seismic stations. However, some glacial earthquakes have been observed at seismic stations within Greenland, but the current station coverage is very sparse. In order to define the fine structure and detailed mechanisms of glacial earthquakes within the Greenland Ice Sheet, a broadband, real-time seismic network needs to be installed throughout the Ice Sheet and perimeter. Because of the long durations of sliding, these glacial earth-quakes do not appear in standard earthquake catalogs, and are best detected by broadband seismometers, which accurately measure both fast (< second) and slow (> 100sec) vibrations. Through denser close-in coverage, the magnitude threshold for detecting glacial earthquakes may be reduced by about one magnitude unit (an order of magnitude in size) with concomitant improvements for locating the event accurately. Such seismic monitoring of the Greenland Ice Sheet via glacial earthquakes will complement both surficial GPS monitoring and remote sensing from satellites, by providing sensitivity to the dynamics of the glaciers at basal depths. In addition, real-time detec-tion of glacial earthquakes permits rapid response and focusing of other sensing techniques to the dynamic region of the Ice Sheet.To achieve good resolution of glacial earthquakes associated with Greenland Ice Sheet dynamics, an internationally coordinated network of 15-25 stations has been proposed to augment existing station coverage within and near Greenland. International participation is essential for success in monitoring Greenland Ice Sheet dynamics, though the IRIS Consortium from the USA will provide the bulk of the instrumentation, development and mainte-nance costs. The planned coastal and interior sites within Greenland incorporate and build upon the framework of existing seismic stations of the Geological Survey of Denmark and Greenland (GEUS), and stations jointly operated with Germany’s GeoForschungsZentrum Network (GEOFON) and GSN. In order to build on this basic foundation, international commitments for equipment, real-time telemetry, operations and maintenance, and logistical resources are necessary to initiate, motivate, and sustain a long-term Greenland Ice Sheet monitoring effort. All the data from the GLISN will be openly available to anyone in real-time, without restriction. The Swiss Seismological Service (SED), ETH Zurich, plans to participate in this international project by taking responsibility for one station in the network. The proposal focuses on the procurement of the equipment needed for this station to be located on the icesheet - 2 triaxial broadband seismometers for surface and borehole, GPS receiver, Iridium communications equipment, Lithium thionyl battery pack, and solar cells. In addition, SED will contribute to the maintenance and operation of the network with its technical personnel and participate in the various research projects that will build upon data collected by this network.