MELT REGIMES, INTERNAL STRATIGRAPHY, AND FLOW DYNAMICS OF THREE GLACIERS IN THE ALASKA RANGE

MELT REGIMES, INTERNAL STRATIGRAPHY, AND FLOW DYNAMICS OF THREE GLACIERS IN THE ALASKA RANGE

By Seth William Campbell

Thesis Advisor: Dr. Karl Kreutz

A Lay Abstract of the Thesis Presented

in Partial Fulfillment of the Requirements for the

Degree of Master of Science

(in Earth Sciences)

August, 2010

Mountain and alpine valley glaciers are often described by their thermal characteristics which are heavily influenced by environmental factors such as elevation, amongst others.  For example, low elevation glaciers that experience melting throughout the snow pack are in the wet snow zone. Conversely, higher elevation glaciers that experience some melting and refreezing, or no melting, are in the percolation and dry zones, respectively.  Defining boundary elevations between these melt regimes is a fundamental step to determine where melting occurs, locally (glacier scale) and regionally (mountain range scale).  Secondly, ice cores, a major source of past climate information, require glacier ice which have experienced minimal melting and deformation.  Herein, I use geophysical, geodetic, and geochemical evidence collected from three glaciers in the Alaska Range, to estimate melt regime boundary elevations, regionally.  I then compare features of the three glaciers using the same evidence to make recommendations for potential ice core drill sites based on pre-determined drilling criteria. 

Results from the Yentna Glacier, Mount Russell (2770 masl), suggest significant melt throughout the snow pack implying that this elevation is within the wet snow zone and hence, an inappropriate ice core site.  A ground penetrating radar profile collected along the centerline of the Kahiltna Glacier, Mount McKinley between 3350-2340 masl show a transition between significant melt (wet zone) and minimal melt (percolation zone) near 2800 masl.  This suggests that the site on Mount Russell may be located just below the percolation-wet zone transition.  Data from Kahiltna Pass Basin on Mount McKinley (3100 masl) show minor melt and refreezing, suggesting this elevation is toward the upper region of the percolation zone.  Minor melting is not a major ice coring deterrent however, evidence of structural complexities associated with significant deformation preclude the basin as an appropriate site to obtain a multi-century core.  Lastly, an ice divide on Mount Hunter (3907 masl) shows no signs of melt which is indicative of the dry snow zone. Thick ice (~270 m) and few signs of deformation suggest that the divide may contain a useful multi-century climate record.