Matanuska Glacier Cave Project, Chugach Mountains, Alaska, USA – October 2007 -Jason Gulley (NSS #49938)

At the turn of the century, glaciologists discovered that glaciers at the edge of the Greenland Ice Sheet were accelerating in response to increased melting at the periphery. This discovery had profound implications for the predicted rate of global sea level rise in response to global climate change. While previously scientists had thought ice sheets would gradually respond to increasing surface temperatures over a period of centuries, this new data indicated that the Greenland was already responding to climate change. Increased glacier velocities are particularly worrisome because faster-moving glaciers can transfer ice from higher elevations with colder temperatures to lower, warmer elevations where it can melt faster or be transferred directly from land to the ocean by calving off icebergs. Meltwater is known to reach the bed of much smaller valley glaciers through englacial conduits (glacier caves) and “lubricate” their motion during the melt season, however, glacier hydrological theory did not allow for englacial conduits to occur on the Greenland Ice Sheet. This discrepancy, coupled with the urgent need to make accurate predictions of cryospheric response to global warming, have focused renewed attention on glacier hydrological processes – especially those associated with conduit formation. The Matanuska Glacier, located in the Chugach Mountains, Alaska, USA, is the largest glacier in Alaska that is accessible by car. At 28 miles long and 4 miles wide at the glacier terminus, the Matanuska provides a logistically simple and cost-effective field site to investigate glacier cave processes. The goal of the October 2007 expedition was to investigate a series of deep caves that were discovered during an expedition in September 2006 at the up-glacier end of the compressive glacier tongue. These caves were suspected to form by hydrofracturing, a process that occurs when high water pressures can force fractures deep into the ice, potentially all the way to the glacier bed, and nucleate glacier caves. Unseasonably warm weather in 2007 caused ice screw rappel anchors to rapidly melt out on the surface and created dangerously wet conditions within the caves which blocked all efforts to map them. The 2008 effort was scheduled later in the year and single digit surface temperatures provided the perfect weather for exploration. Our team, consisting of Matt Reece (NSS #28846 – Oregon) Steve Keene (NSS #29507 - Indiana) and Annelie Bergstrom (Sweden), explored and mapped six caves during the two-week effort. The three caves at the top of the compressive tongue were mapped to depths of 65 m of ice. Named Disto Fever, Disto Inferno and Disto, Disto, Disto, the conduits were collectively referred to as the Dance Party caves and formed by a previously undescribed process of hydrofracturing in a region of compressive stress. Previously, conduits with a hydrofracture origin were only thought to form in zones of extensional stress and this discovery expands the range of structural environments on glaciers that can form englacial conduits and helps establish boundary conditions for where meltwater might reach the bed of the Greenland Ice Sheet. Cave maps generated from the 2007 expedition have been combined with glacier cave maps from two other Matanuska expeditions as well as maps from glaciers cave in the Mt Everest region of Nepal and the high arctic archipelago of Svalbard to formulate the first theory of glacier hydrology based on direct observation. Maps from the Matanuska Glacier Cave Project have thus far been used to inform the following two research publications which are presently under review at the Journal of Glaciology: Gulley JD, Benn DI, Muller D, Luckman A. In Review. A cut and closure origin for englacial conduits in uncrevassed regions of polythermal glaciers. Journal of Glaciology. Benn DI, Gulley JD, Luckman A, Adamek A, Glowacki P. In review. Widespread initiation of glacier drainage by hydrofracturing. Journal of Glaciology.					Annelie Bergstrom near the end of Disto Fever
					Annelie Bergstrom at the end of Disto Fever
					Annelie Bergstom in one of Disto Fever’s many migrating nickpoints
Traversing to a drop in Disto, Disto, Disto	The entrance drop to Disto Inferno	The entrance to Disto Inferno	Steve Keene negotiates a series of breached meander bends in Disto Disto Disto	Steve Keene exits Disto Inferno	Matt Reece at the top of Disto Inferno entrance sequence