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Subglacial Access and Fast Ice Research Experiment (SAFIRE)

Subglacial Access and Fast Ice Research Experiment (SAFIRE)

The Greenland ice sheet contains 3 million cubic kilometres of ice and has been losing mass at an accelerating rate since 1990 (1). Due to increased surface melting (2) and discharge of ice into the ocean (3), and with more precipitation falling as rain (4), there is a net loss of ice, which has intensified from -50 km3/year per year in 1990s to -200 km3/year in the 2000s to -300 km3/year since 2010 (2, 3, 5). Today, the Greenland ice sheet is raising sea level by 1 mm per year (2), which makes it the most significant contributor in the global Cryosphere.

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Cumulative ice mass loss and sea level equivalent (SLE) due to surface melting and discharge of ice (From Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change Climate Change, 2013)

Fast flowing glaciers

Glaciers terminating in fjords and coastal seas drain 88% of the Greenland Ice Sheet. These glaciers amongst the fastest in the world and they are responsible for up to two-thirds of the ice sheet's contribution to sea level rise (6). Understanding the processes that drive the fast flow of these glaciers is crucial because a growing body of scientific evidence points to a strong, but spatially varied, and often complex response to changes in the ocean as well as the atmosphere. So far, no observations have ever been made from beneath a marine-terminating glacier in Greenland, a potential and likely cause of significant error in current predictions of future sea levels. The SAFIRE project addresses this problem by gaining access to the basal zone and bed of Store Gletscher, a major outlet glacier in West Greenland.

"With no previous observation ever made in a subglacial environment of this type of glacier, this project breaks new ground."

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Flow of the Greenland Ice Sheet. Dashed line and 'Store' show catchment of glacier studied in the SAFIRE project (background image showing MEaSUREs velocity data was produced by NASA)

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The 5-km-wide front of Store Glacier in West Greenland. The glacier terminus extends to a depth of 500 m and flows at a rate of 20 m per day (photo by Poul Christoffersen)

The SAFIRE project

The rationale of this project is to investigate mechanical and hydrological conditions at the bed of a large marine-terminating glacier in Greenland in order to understand the sensitive response of these glaciers to changes in environmental stimuli, whether atmospheric or oceanographic. Underpinning the rationale further is the fact that very little is known about subglacial environments in Greenland. It is commonly assumed that all glaciers in Greenland slide over hard and impermeable bedrock, but this is simply a practical assumption based on lack of better constraints. The fast glacier flow could also be a result of lubrication of weak sediment at the bed. This project will resolve this fundamental unknown by drilling to the bed of Store Glacier in West Greenland. With instruments deployed at the bed and within boreholes, the team of investigators will fully resolve the basal control on fast glacier flow in Greenland.

The SAFIRE project has two specific goals. The first is to identify and characterise the mechanical and hydrological conditions at the base of a large outlet glacier in Greenland, using instruments installed in boreholes drilled to the bed. With no previous observation ever made in a subglacial environment of this type of glacier, this project breaks new ground. The chosen glacier is Store Gletscher (meaning 'Big Glacier' in Danish and henceforth referred to as 'Store'), which drains 35,000 km2 and flows at a rate of 20 m per day where it reaches the sea.

The second goal of SAFIRE is to determine the role of basal processes in governing ice flow and iceberg calving. To achieve this goal the investigators will use data acquired from instruments deployed in boreholes and on the glacier's surface as a means to constrain numerical ice-flow models.

The SAFIRE project is a joint project between the University of Cambridge and Aberystwyth University in Wales.

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Scientists onboard 'Gambo' measure salinity and temperature of seawater near the front of Store Glacier (photo by Alun Hubbard)

References

  1. IPCC, Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. T.F. Stocker et al., Eds., (Cambridge University Press, Cambridge, UK, and New York, USA, 2013), pp. 1535.
  2. E. M. Enderlin et al., Geophysical Research Letters 41, 866 (2014).
  3. E. Rignot, P. Kanagaratnam, Science 311, 986 (2006).
  4. S. H. Doyle, A. Hubbard, R. S. W. van de Wal, e. al., Nature Geoscience 8, 647 (2015).
  5. A. Shepherd et al., Science 338, 1183 (2012).
  6. M. van den Broeke et al., Science 326, 984 (2009).
  7. J. Todd, P. Christoffersen, Cryosphere 8, 2353 (2014).
  8. M. O'Leary, P. Christoffersen, Cryosphere 7, 119 (2013).
  9. J. C. Ryan et al., Cryosphere 9, 1 (2015).
  10. M. Bougamont et al., Nature Communications 5, (2014).
  11. S. H. Doyle et al., Geophysical Research Letters 41, 899 (2014).