Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

10-2013

Journal or Book Title

Geology

Issue

G34760.1

First Page

1

Last Page

31

DOI

10.1130/G34760.1

Abstract

Many of the key processes governing fast glacier flow involve interaction between a glacier and its basal hydrological system, which is hidden from direct observation. Passive seismic monitoring has shown promise as a tool for remotely monitoring basal processes, but lack of glacier-bed access prevents clear understanding of the relationships between subglacial processes and corresponding seismic emissions. Here we describe direct measurements of basal hydrology, sliding, and broadband seismicity made in a unique subglacial facility in Norway during the onset of two summer melt seasons. In the most pronounced of these episodes, rapid delivery of surface meltwater to the bed briefly enhanced basal slip following a period of elevated high-frequency seismic activity related to surface crevassing. Subsequent ground tilt derived from ultralong-period seismic signals was associated with subglacial bedrock deformation during transient pressurization of the basal hydraulic system. These signals are interpreted to represent hydraulic jacking as the supply of water to the bed exceeded the capacity of the hydraulic system. Enhanced slip terminated 2.5 h after it started, when ice-bed decoupling or increased connectivity in the basal cavity network relieved cavity overpressure. The results support theoretical models for hydraulic jacking and illustrate how melt-induced increases in speed can be short lived if cavity growth or ice-bed decoupling allows basal water more efficient drainage.

Comments

This is a manuscript of an article from Geology (2013): art. no. G34760, doi:10.1130/G34760.1. Posted with permission.

Copyright Owner

Peter L. Moore, et al

Language

en

File Format

application/pdf