This research project, conducted in close collaboration with scientists at the Polish Polar Station in Hornsund, is helping fill a significant gap in knowledge by using caving techniques to make detailed, three-dimensional maps of glacier hydrological systems and simultaneously conducting Ground Penetrating Radar (GPR) surveys over the mapped conduit systems. The speleological maps provide key information about passage morphology that helps interpret the geophysical data. By ‘calibrating’ the GPR reflectors to known conduit morphologies, this study will help interpret GPR data from glaciers where conduit systems are not directly accessible (such as deep portions of the Greenland Ice Sheet).

Fieldwork was conducted between September 1st and October 12th on Hansbreen and Werenskioldbreen in Hornsund and between Oct 13th and November 5th at Rieperbreen (in Bolterdalen, near Longyearbyen). During fieldwork at Hornsund ~9 englacial conduits were investigated. Most englacial conduits were simple moulins that became too constricted to continue after reaching depths of about 30 meters. Two englacial conduits led to extensive englacial and subglacial conduit systems. Both conduit entrances were located in ice marginal lake basins at glacier confluences. The englacial conduits are interpreted to have formed by hydrofracture in zones of longitudinal extension.

The first conduit system the group investigated formed at the confluence of Fuglebreen and Hansbreen. The conduit descended as a vertical crack through 43 meters of glacier ice before connecting to an extensive, anastomotic system of subglacial conduits ~400 meters long. The subglacial conduit leading away from the hydrofracture followed the bed slope for 54 m before splitting into 5 separate conduits. Preliminary investigation of GPR and conduit survey data indicate that the downstream conduits flowed along the strike of the ice-bed interface rather than down the bedslope as would be predicted by glacier hydrological theory. Conduit cross-sections varied from low, wide crawlways to half-circular passages incised upwards into the ice. In addition to the conduit and GPR surveys, bed roughness surveys were conducted and creep closure rates were measured over a period of one month in each of the conduit sections.

The second conduit system that was mapped was Crystal Cave. The conduit is located in an ice marginal lake at the confluence of Tuvbreen and Hansbreen. A short cut-and-closure conduit led from the lake basin to a hydrofracture formed by longitudinal extension. A system of relict conduits was also accessed from this entrance. Conduit cross-sections in Crystal Cave had been significantly reduced by creep closure since the last mapping project was conducted in 2007. 200 meters of conduit were mapped in Crystal Cave to a maximum ice depth of 60 meters. The bed was not reached during mapping of Crystal Cave because a week of rain at the end of September filled the deeper portions of englacial conduits with water making them inaccessible without diving equipment. GPR surveys were conducted over Crystal Cave as well as in a Moulin field near the front of the glacier. Repeat visits to deepest point of Crystal Cave showed that the water levels were not dropping and that continued exploration of deep cave systems was unlikely to be possible during the 2009 field season.

Following a short reconnaissance trip to two conduits on Werenskioldbreen, fieldwork was shifted to study an extensive conduit system beneath Rieperbreen in mid-October.
Nine potential conduit entrances were investigated on Riperbreen. Most entrances led to areas of the glacier bed that were too small to explore with caving techniques. One entrance, however, led to a relatively short, narrow englacial canyon that connected to an extensive subglacial conduit. The conduit system is interpreted to have formed as a cut-and-closure canyon that has migrated up the glacier. More than 500 meters of englacial and subglacial conduit were mapped and the conduits continued at the furthest point of exploration. It is hoped to finish surveying the conduit system and conduct GPR surveys in April, 2010. Because Rieperbreen has the only subglacial conduit system that has been mapped entirely from recharge point to discharge point, it is an ideal location to groundtruth the interpretation of dye trace breakthrough curves, geophysical imaging techniques and to validate models of the subglacial hydrology.

In future fieldwork, Jason Gulley will conduct dye traces in the conduit system at Rieperbreen in the summer of 2010 to determine if changes in the rate of recharge to a known conduit can generate the same type of dye break through curves that are typically interpreted to indicate a change from distributed subglacial drainage to a conduit system. Additionally, Alison Banwell (an external PhD student at UNIS) will use conduit maps to parameterize and test a model of subglacial hydrology.
Detailed analysis of data collected from this project will begin in January, 2010.

Source & contact: Jason Gulley, University of Florida and UNIS (gulley.jason@gmail.com), Arctic Field Grant Report (AFG2009-472)

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The hydrofracture entrance to JPM at the confluence of Hansbreen and Fuglebreen.

Looking out the hydrofracture entrance to JPM.

Nye channel incised in frozen till beneath Rieperbreen (all photos: Jason Gulley)