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Glacial isostatic adjustment in response to changing Late Holocene behaviour of ice streams on the Siple Coast, West Antarctica

Citation

Nield, GA and Whitehouse, PL and King, MA and Clarke, PJ, Glacial isostatic adjustment in response to changing Late Holocene behaviour of ice streams on the Siple Coast, West Antarctica, Geophysical Journal International, 205, (1) pp. 1-21. ISSN 0956-540X (2016) [Refereed Article]


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Copyright Statement

Copyright 2016 The Authors Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.1093/gji/ggv532

Abstract

The Siple Coast region of Antarctica contains a number of fast-flowing ice streams, which control the dynamics and mass balance of the region. These ice streams are known to undergo stagnation and reactivation cycles, which lead to ice thickness changes that may be sufficient to excite a viscous solid Earth response (glacial isostatic adjustment; GIA). This study aims to quantify Siple Coast ice thickness changes during the last 2000 yr in order to determine the degree to which they might contribute to GIA and associated present-day bedrock uplift rates. This is important because accurate modelling of GIA is necessary to determine the rate of present-day ice-mass change from satellite gravimetry. Recently-published reconstructions of ice-stream variability were used to create a suite of kinematic models for the stagnation-related thickening of Kamb Ice Stream since ∼1850 AD, and a GIA model was used to predict present-day deformation rates in response to this thickening. A number of longer-term loading scenarios, which include the stagnation and reactivation of ice streams across the Siple Coast over the past 2000 yr, were also constructed, and used to investigate the longer term GIA signal in the region. Uplift rates for each of the ice loading histories, based on a range of earth models, were compared with regional GPS-observed uplift rates and an empirical GIA estimate. We estimate Kamb Ice Stream to have thickened by 70130m since stagnation ∼165 years ago. Modelled present-day vertical motion in response to this load increase peaks at −17mmyr1 (i.e. 17mmyr1 subsidence) for the weakest earth models tested here. Comparison of the solid Earth response to ice load changes throughout the last glacial cycle, including ice stream stagnation and reactivation across the Siple Coast during the last 2000 yr, with an empirical GIA estimate suggests that the upper mantle viscosity of the region is greater than 1 1020 Pa s. When upper mantle viscosity values of 1 1020Pa s or smaller are combined with our suite of ice-load scenarios we predict uplift rates across Siple Coast that are at least 4mmyr1 smaller than those predicted by the empirical GIA estimate. GPS data are unable to further constrain model parameters due to the distance of the GPS sites from the study area. Our results demonstrate that Late Holocene ice load changes related to the stagnation and reactivation of ice streams on the Siple Coast may play a dominant role in defining the present-day uplift signal. However, both the detailed Earth structure and deglacial history of the region need to be better constrained in order to reduce uncertainties associated with the GIA signal of this region.

Item Details

Item Type:Refereed Article
Keywords:glacial isostatic adjustment, Antarctica, Late Holocene, satellite geodesy, transient deformation, glaciology, dynamics of lithosphere and mantle, rheology, mantle
Research Division:Engineering
Research Group:Geomatic Engineering
Research Field:Geodesy
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:King, MA (Professor Matt King)
ID Code:106796
Year Published:2016
Funding Support:Australian Research Council (FT110100207)
Web of Science® Times Cited:1
Deposited By:Geography and Spatial Science
Deposited On:2016-02-22
Last Modified:2017-10-24
Downloads:29 View Download Statistics

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