HR: 0830h
AN: C31C-0411    [PDF]
TI: Can the recent thinning and acceleration of Pine Island Glacier, West Antarctica be explained by changes in its ice shelf?
AU: * Payne, A J
EM: a.j.payne@bristol.ac.uk
AF: Centre for Polar Observation and Modelling, School of Geographical Sciences University of Bristol University Road, Bristol, BS8 1SS United Kingdom
AU: Vieli, A
EM: a.vieli@bristol.ac.uk
AF: Centre for Polar Observation and Modelling, School of Geographical Sciences University of Bristol University Road, Bristol, BS8 1SS United Kingdom
AB: There is a wealth of evidence implying that Pine Island Glacier, West Antarctica (PIG) is presently undergoing rapid change. Much of this evidence is associated with PIG's ice shelf and ice plain. This includes a retreat of the grounding line by 5 km from 1992 to 1994; a contemporaneous acceleration of flow in the same area by 18%; as well as various calving and crevassing events over the last 30 years. One of the most intriguing observations is of widespread thinning over PIG's full extent up to 150 km upstream of the grounding line at rates of approximately 0.5 m/yr. If this thinning has been caused by the ice shelf/plain changes then it implies a far closer linkage between grounded and floating ice than previously thought possible. We investigate this possibility by using a three-dimensional, numerical model of ice flow. The model incorporates the temporal changes in ice thickness generated by changes in ice flow. We investigate coupling between PIG and its ice shelf in a series of perturbation experiments in which the shelf is thinned and shortened, and the grounding of the ice plain is reduced. Results imply a two-stage process in which initial changes in the shelf have an immediate, mechanical effect up to 50 km inland from the grounding line. These changes are sufficient to initiate a kinematic wave of thinning, steepening ice that propagates rapidly (approximately 5 km/yr) upstream and affects the entire ice stream after approximately 20 years. The propagation mechanism of this wave is the increase in gravitation driving stress consequent on local steepening of the ice surface, which feeds directly into the force balance determining the velocity of the ice stream.
DE: 1620 Climate dynamics (3309)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 9310 Antarctica
SC: Cryosphere [C]
MN: 2003 Fall Meeting