UK ANTARCTIC SEISMIC & GNSS NETWORK

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 WAIS are currently hindered by uncertainties in measurements of present-day ice mass change. Two key methods for deriving this change are 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 meaurements caused just by ice mass change is challenging: both measurements reflect a combination of Earth structures and processes, the most problematic of which is Glacial Isostatic Adjustment (GIA).

 

During GIA, mass within the Earth’s mantle slowly flows back toward equilibrium following the addition (advance) or subtraction (retreat) of a significant surface ice load. The extreme viscosity of the Earth’s mantle means that this internal mass re-distribution can lag the actual ice sheet advance or retreat by thousands of years. Therefore, we can only isolate the gravity and altimetry signals caused by present ice mass change by removing the GIA signal caused by the past behaviour of the ice sheet. To do this, we must know both the ice sheet history and the viscosity of the mantle.

The West Antarctic Ice Sheet

How viscous is the upper mantle?

Temperature is considered the dominant control on mantle viscosity. Since seismic wave propagation in the Earth is particularly sensitive to thermal variations, seismology is an ideal tool to probe mantle viscosity. The UKANET seismic network consists of 10 broadband stations located across the southern Antarctic Peninsula and Ellsworth Land in West Antarctica that will record seismic energy from earthquakes occurring worldwide over a two-year period. Analysis of the data will ultimately recover the thermal signature (and hence viscosity) of the underlying mantle encoded in the recorded waveforms. Combined knowledge of mantle viscosity, ice sheet history and current uplift rates determined by the UKANET sister Global Navigation Satellite System (GNSS) network and satellite radar interferometry data (InSAR) will permit WAIS evolution to be more accurately predicted.

 

Seismic data have never been collected in the southern Antarctic Peninsula region of West Antarctica, and hence very little is known about its Earth structure. In addition to determining mantle viscosity, the UKANET seismic network will probe lithospheric structure and shed light on the tectonic evolution of the region.

​UKANET is funded by the Natural Environment Research Council 

Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.

British Antarctic Survey, High Cross, Madingley Rd, Cambridge CB3 0ET, UK.

Department of Geography, Durham University, Lower Mountjoy South Road, Durham, DH1 3LE, UK 

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