Spatial and temporal variations in surface velocity and basal drag across the tongue of the polythermal glacier midre Lovenbreen, Svalbard

TY - JOUR

T1 - Spatial and temporal variations in surface velocity and basal drag across the tongue of the polythermal glacier midre Lovenbreen, Svalbard

AU - Rippin, D. M.

AU - Willis, I. C.

AU - Arnold, N. S.

AU - Hodson, A. J.

AU - Brinkhaus, M.

PY - 2005

Y1 - 2005

N2 - We present results of a detailed investigation of surface motion across the tongue of a polythermal glacier, midre Lovenbreen, Svalbard, during the 1999 summer. Surface velocities in the warm-based upper tongue increased during periods of enhanced surface melting and rainfall events, and force-balance analysis indicates that these velocity variations were locally forced, probably by fluctuations in subglacial water pressure. Surface speed-ups were also observed on the cold-based lower tongue (which acted as a sticky spot, through which there was minimal subglacial drainage for most of the summer), but these were largely non-locally forced by longitudinal coupling to the faster-moving ice up-glacier. On one occasion, however, a large, rapid input of surface water to the glacier reduced the basal drag beneath the cold-based lower tongue, presumably due to hydraulic jacking. This resulted in locally forced enhanced surface velocities across the entire tongue, accompanied by a breaching of the lower tongue and an outburst of subglacially stored water.

AB - We present results of a detailed investigation of surface motion across the tongue of a polythermal glacier, midre Lovenbreen, Svalbard, during the 1999 summer. Surface velocities in the warm-based upper tongue increased during periods of enhanced surface melting and rainfall events, and force-balance analysis indicates that these velocity variations were locally forced, probably by fluctuations in subglacial water pressure. Surface speed-ups were also observed on the cold-based lower tongue (which acted as a sticky spot, through which there was minimal subglacial drainage for most of the summer), but these were largely non-locally forced by longitudinal coupling to the faster-moving ice up-glacier. On one occasion, however, a large, rapid input of surface water to the glacier reduced the basal drag beneath the cold-based lower tongue, presumably due to hydraulic jacking. This resulted in locally forced enhanced surface velocities across the entire tongue, accompanied by a breaching of the lower tongue and an outburst of subglacially stored water.

KW - SUBGLACIAL WATER-PRESSURE

KW - DRAINAGE SYSTEM

KW - FORCE BUDGET

KW - MASS-BALANCE

KW - ICE SHEETS

KW - SURGE-TYPE

KW - MOTION

KW - COLD

KW - FLOW

KW - SWITZERLAND

M3 - Article

SN - 0022-1430

VL - 51

SP - 588

EP - 600

JO - Journal of Glaciology

JF - Journal of Glaciology

IS - 175

ER -