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Research outcomes

Since 2014, the SAFIRE project has been monitoring the dynamics of iceberg calving while also measuring ice flow and properties at the bed.

Subglacial access drilling and borehole investigations

In 2014, the SAFIRE team drilled four boreholes to the bed of Store Glacier with a hot-water drill. The boreholes were more than 600 m deep and all four connected instantly with a basal water system when the drill stem reached the bed. The team is now monitoring changes in water pressure, turbidity and electrical conductivity from sensors installed at the bed in a region where ice flows at a rate of 3 m per day at the surface. The team has shown that deep boreholes can be drilled on crevassed and fast flowing glaciers.

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Hot-water drilling on Store Glacier in July 2014. (Photo by Poul Christoffersen)

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3D diagram of Store Glacier (above) showing ice flow and bed and location where boreholes were drilled in 2014. Photograph (below) shows cable with sensors installed in 600+ m borehole. (Photo by Poul Christoffersen)

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In 2014, the team also inserted cables with thermistors and tilt cells into the boreholes. These sensors inform temperature and deformation of ice.

Surface geophysics

On the surface, the team is recording ice flow with a network of GPS while simultaneously recording atmospheric conditions with an automatic weather station provided by Prof. Jason Box, a collaborator at the Geological Survey of Denmark and Greenland. The team also carried out a seismic survey with help and hardware from Coen Hofstede, a collaborator at the Alfred Wegener Institute. The team is also trialing the use of autonomous phase-sensitive radio-echo sounding (ApRES) as tool to monitor basal melting and ice deformation in high temporal (hourly) resolution.

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Sam Doyle and Tun Jan "TJ" Young setting up ApRES imaging radar on Store Glacier in May 2014. (Photo by Poul Christoffersen)

Glacier surveillance with UAV

In 2014, a second field camp was set up near the calving front of Store Glacier. From early May to late July, team members consisting mainly of PhD students carried out a detailed surveillance programme using unmanned aerial vehicles (UAVs). With 100,000+ images acquired sequentially in 60+ missions, the team has recorded the calving mechanism with data in unprecedented temporal resolution and detail.

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(Above and below) Johnny Ryan and Nick Toberg (PhD students supported by SAFIRE) launch UAV. The team spent three months surveying the calving front of Store in 2014 (Photos by Nick Toberg).

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Image mosaic of Store Glacier from UAV survey on 16 May 2014:

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Close up of Store Glacier from UAV survey on 16 May 2014:

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Numerical modelling

To determine the role of basal processes in governing ice flow and iceberg calving the SAFIRE team uses numerical ice-flow models constrained by data acquired by satellites, UAVs, surface geophysics, automatic weather station data and sensors deployed in boreholes.

The first set of results from numerical modelling was produced from a 2D model of ice flow along the centreline of Store Glacier. This model showed that seasonal variability in ice-front position and calving rate are primarily governed by the support provided by icebergs, bergy bits and sea ice, which forms a rigid melange in front of the glacier in winter months (7). Undercutting of the ice-front by melting of ice in contact with sea water - a potentially powerful mechanism (8) - plays a secondary role in our simulations because the flux of ice into the ocean is extremely high. Our UAV surveys show that Store Glacier puts 33 million cubic metres of ice is put into the ocean every day (9).

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Vertical profiles of Store Glacier from 2D simulation with Elmer/ICE. The profiles show advance of the terminus and formation of a floating tongue in winter when the front is buttressed by rigid proglacial mélange. Dashed lines show extent of downward propagation of surface crevasses and upward propagation of basal crevasses. See (7) for details.

The SAFIRE team is now developing 3D models of Store Glacier using the Community Ice Sheet Model (CISM) and Elmer/ICE.

Animation

3D finite element grid of Store Gletscher used by Joe Todd (PhD student supported by SAFIRE)