Helheim 2006 An investigation of glacial earthquakes

Updates (latest: 2006/08/23):

• Satellite tracker data:
  Motion of sites through 2006/08/12 from satellite trackers
  
  
  
• Trip 2 (maintenance and data download):
  All of the stations on the ice and two of the rock sites were visited July 22-24, 2006. One ice station (IS03) was found in a precarious position and was removed, leaving 15 ice sites and 3 rock sites in the network. The geometry of the ice surface had changed substantially since our installation visit, and the calving front appeared to be retreating. Our visit coincided with the peak of the melt season, and running and standing water were conspicuous features of the glacier surface.
  
  
  • Map showing station locations at time of maintenance visit, compared with at time of deployment
    
    
    
  • Photos from the trip
    
  
  

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• Trip 1 (instrument deployment):
  Sixteen Global Positioning System (GPS) systems were deployed at sites on Helheim Glacier June 27-30, 2006. Three systems were also installed at rock sites nearby.
  
  
  • Map of sites deployed
    
    
    
  • Photos from the trip (more photos added 2006/07/10)
    

Project overview:

The main goal of the Helheim 2006 project is to obtain an understanding of the mechanisms by which glacial earthquakes are generated, and of their relation to glaciological and climatological processes.

A new class of earthquakes occurring at glaciers in Alaska, Antarctica, and Greenland was identified in 2003 by Ekström et al. (2003). Teleseismic analysis indicates that these glacial earthquakes are the result of rapid sliding of the glacial ice over the glacier bed; during each sliding episode, a 10-km³ volume of ice may slide as far as 10 meters during a period of 30-60 s. Little is understood about the mechanism by which glacial earthquakes occur, but recent observations indicate a relationship with the hydrological cycle at glaciers and ice sheets. The number of earthquakes that occur on Greenland is strongly seasonally modulated, with the largest number of events occurring during the late summer months. A rapid increase in the number of earthquakes at outlet glaciers across Greenland since approximately 2000 suggests a link to large-scale climate change.

The Helheim 2006 research project consists of two main parts: (1) a field deployment of Global Positioning System (GPS) stations on Helheim Glacier, East Greenland, to obtain direct measurements of the displacement transients associated with glacial earthquakes; and (2) integrated, interdisciplinary analysis of recorded GPS, seismic, and glaciological data using state-of-the-art techniques from each field to obtain an understanding of the mechanism by which glacial earthquakes occur. Seismic analyses will provide long-wavelength estimates of the earthquake source characteristics, while the geodetic observations will provide detailed information about the timing and pattern of deformation within the glacier. A combined analysis of these datasets will result in geophysically consistent models of the deformation process, which will then be studied in the context of glaciological observations of the background glacier behavior and time-varying melting rates to evaluate the hypothesis that surface melting is linked to the generation of glacial earthquakes.

Participants:

Columbia University/LDEO, USA: Meredith Nettles, Göran Ekström, Morten Langer	Geological Survey of Denmark and Greenland (GEUS), Denmark: Andreas P. Ahlstrøm, Tine B. Larsen, Thomas Møller Jørgensen	Danish National Space Center (Danmarks Rumcenter), Denmark: René Forsberg, Lars Stenseng Shfaqat Abbas Khan
Harvard-Smithsonian Center for Astrophysics, USA: James L. Davis	Institute for Space Sciences, CSIC/IEEC, Spain: Pedro Elósegui	University of Maine, USA: Gordon Hamilton, Leigh Stearns

Project funding and logistical support:

Gary Comer Science and Education Foundation	U.S. National Science Foundation	The Commission for Scientific Research in Greenland (KVUG)
Danish National Space Center	Spanish Ministry of Education and Science (MEC)	LDEO Climate Center
NASA		The Dan and Betty Churchill Exploration Fund

The GPS systems and used for the Helheim 2006 project were provided by UNAVCO. Shipping of the instruments to Greenland was managed by UNAVCO and VECO Polar Resources.

The Helheim 2006 project is supported by the Gary Comer Science and Education Foundation, the U.S. National Science Foundation (OPP-0612609), the Geological Survey of Denmark and Greenland (GEUS), Geocenter Copenhagen, the Danish Commission for Scientific Research in Greenland (KVUG), the Spanish Ministry of Education and Science (CGL2005-25079-E), the Danish National Space Center, NASA (NNG04GL69G, NNG04GK39G), the Lamont-Doherty Climate Center, and the Dan and Betty Churchill Exploration Fund.
[Note: Any opinions, findings and conclusions or recomendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation (NSF) or any other institution or organization providing support.]