Basal conditions and glacier motion during the winter/spring transition, Worthington Glacier, Alaska, U.S.A.

• Published in: Journal of Glaciology
• Main Authors: Harper, Joel T., Humphrey, Neil, Greenwood, Mark C.
• Format: Text
• Language: unknown
• Published: ScholarWorks at University of Montana 2002
• Subjects: Earth Sciences; Glaciology; glacier; Alaska
• Online Access: https://scholarworks.umt.edu/geosci_pubs/28; https://doi.org/10.3189/172756502781831629; https://scholarworks.umt.edu/context/geosci_pubs/article/1030/viewcontent/Basal_conditions_and_glacier_motion_during.pdf

Observations of the motion and basal conditions of Worthington Glacier, Alaska, U.S.A., during late-winter and spring melt seasons revealed no evidence of a relationship between water pressure and sliding velocity. Measurements included borehole water levels (used as a proxy for basal water pressure), surface velocity, englacial deformation, sliding velocity, and time-lapse videography of subglacial water flow and bed characteristics. The boreholes were spaced 10-15 m apart; six were instrumented in 1997, and five in 1998. In late winter, the water-pressure field showed spatially synchronous fluctuations with a diurnal cycle. The glacier's motion was relatively slow and non-cyclic. In spring, the motion was characterized by rapid, diurnally varying sliding. The basal water pressure displayed no diurnal signal, but showed high-magnitude fluctuations and often strong gradients between holes. This transition in character of the basal water-pressure field may represent a seasonal evolution of the drainage system from linked cavities to a network of isolated patches and conduits. These changes occurred as the glacier was undergoing a season-velocity peak. The apparent lack of correlation between sliding velocity and water pressure suggests that local-scale water pressure does not directly control sliding during late winter or early in the melt season.