Rothera Point, Adelaide Island

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Rothera Point, Adelaide Island

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IMG_2889
IMG_2889

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Rothera Point, Adelaide Island

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UK ANTARCTIC GNSS & SEISMIC NETWORK

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The West Antarctic Ice Sheet

The West Antarctic Ice Sheet

Ice loss from the West Antarctic Ice Sheet (WAIS) currently accounts for around 10% of global sea-level rise. Moreover, this region is undergoing accelerated ice loss. Accurate projections for the evolution of the WAIS are currently hindered by uncertainties in measurements of present-day ice mass change and incomplete understanding of the feedbacks between ice sheet dynamics and deformation of the land beneath the ice sheet.

 

Two key methods are used to determine contemporary ice sheet change: satellite gravimetry, which determines changes in Earth's gravity field due to mass redistribution, and altimetry, which measures modifications to the height of the ice surface. However, isolating the part of the gravity and altimetry measurements that is just due to ice mass change is challenging because both also contain a signal due to Glacial Isostatic Adjustment (GIA).

 

During GIA, the surface of the Earth deforms as mass within Earth’s mantle slowly flows back toward equilibrium following the growth and retreat of the ice sheet. The extreme viscosity of Earth’s mantle means that this process can lag the actual ice sheet advance or retreat by thousands of years, but in regions of weak mantle viscosity the process can take place over centuries or decades, rapidly altering the boundary conditions controlling ice flow. This project seeks to quantify the rheological properties of the mantle beneath Antarctica.

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UKANET: project structure

The first UKANET project (2014-2018) was led by Graham Stuart (University of Leeds). The focus of this project was the deployment of 10 broadband seismometers across the southern Antarctic Peninsula and Ellsworth Land. The instruments recorded seismic energy from earthquakes occurring worldwide over a two-year period. Seismic data had not previously been collected in this region, and hence very little was known about the local Earth structure. Analysis of seismic wave propagation was used to infer spatial variations in the thermal properties, and hence the viscosity, of the mantle. In addition to providing constraints on mantle viscosity, the UKANET seismic network was used to probe lithospheric structure and shed light on the tectonic evolution of the region. Preliminary modelling of the impact of spatial variations Earth structure on the GIA process was carried out.

 

The second UKANET project (2018-) is led by Pippa Whitehouse (Durham University). The focus of this project is the UK Antarctic GPS network, which extends from the tip of the Antarctic Peninsula to the Shackleton Mountains in East Antarctica. Time series analysis and geodynamic modelling will be carried out to infer the rheological properties of the Earth beneath Antarctica, drawing on data-constrained reconstructions of recent and contemporary ice sheet change.