Quantifying West Antarctic mantle viscosity via precise GPS measurement of Earth's response to surface mass balance anomalies

Satellite measurements of ice sheet change are necessary to understand and help predict sea level rise, but are contaminated by a phenomenon known as Glacial Isostatic Adjustment (GIA). GIA is a form of ongoing solid Earth deformation in response to previous ice sheet mass changes. It can in principle be measured wherever we have access to bedrock, but this is not the case for much of Antarctica and therefore (and also for reasons of practicability) we require physically-based mathematical models of GIA. These models must be calibrated and validated, which can be done with the aid of precise measurements of Earth deformation made using continuous GPS receivers sited on bedrock.

Continuous GPS data are therefore crucial to the determination of past and present ice mass change across Antarctica and the quantification of feedbacks between ice dynamics and solid Earth deformation. A fundamental property that must be quantified in such studies is the rheology of the solid Earth (its deformational response to forces acting on it). The Earth's mantle shows viscous behaviour over longer timescales but behaves elastically in the short term (as observed e.g. by the passage of seismic waves), a phenomenon known as viscoelasticity. Recent studies have demonstrated that there are large spatial variations in mantle viscosity across Antarctica, but at present the magnitude of such variations is not known. We propose to pioneer a new approach to determining spatially-variable mantle viscosity that involves analysing the viscoelastic response of the solid Earth to episodic surface mass balance (SMB) anomalies across Antarctica. Our approach makes use of the fact that in regions where the magnitude of surface mass change is well known, observations of the accompanying solid Earth response allow the quantification of the rheological properties of the Earth.

In order to achieve our goal we require access to high-precision, long-duration GPS records. Fortunately there is already an extensive GPS network in West Antarctica, which although erected piecemeal via a series of NERC-funded projects (and equivalent overseas grants), now has the potential to deliver such records over the next few years. We therefore propose to overhaul the existing GPS network that lies within the remit of UK logistical support in Antarctica; we will extend the time series at a strategic subset of the existing sites, and transmit all data to open access servers via satellite. The resulting step change in precision and data accessibility will enable us to achieve our scientific goals and at the same time will benefit the international scientific community: the provision of open access GPS time series for West Antarctica will contribute to emerging data inversion activities and make it possible to ground-truth ice mass balance estimates delivered by the multi-million-dollar Gravity Recovery and Climate Experiment (GRACE) Follow-on mission, which is due for launch in 2017.

The main component of our pathways to impact plan is motivated by our use of cutting-edge satellite technology to collect and transmit data from remote locations around Antarctica. Building on our previous experience of working with an experienced science communicator, we will develop a series of novel cross-curricular STEM-related activities that will address curriculum learning targets, while at the same time providing secondary school pupils with the opportunity to engage first-hand with the technological solutions that are used to deliver modern polar research.

Who? These activities will benefit secondary school teachers and pupils

How? The activities will be designed to boost teacher confidence and provide pupils with real-world examples of applying STEM-related skills. Teacher confidence will be enhanced via CPD events, where the motivation behind the different activities will be explained, and tips will be given on how to deliver them.
How? Pupils will benefit from being exposed to real-world uses for skills associated with engineering, mathematics, geography and computing. By designing activities that call for pupils to use their problem-solving skills, these sessions should be more memorable than activities based purely around the delivery of information. Also, by designing tasks that are achievable, it is hoped that the experience will provide positive feedback to pupils with regard to their STEM-based capabilities. The fun nature of the tasks should also help to challenge common assumptions that STEM subjects are boring or difficult.

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Who? A number of activities associated with our project will also benefit the scientific community.

How? We will provide access to freely-available, near real-time GPS data from 22 locations across Antarctica. This resource will enhance the research capabilities of scientists working in the fields of cryosphere, sea-level change, geodesy, and geophysics. Access to the GPS data will lead to better quantification of the solid Earth response to surface loading, and hence an improved understanding of the processes governing contemporary ice sheet change.

How? We will also promote the rapid dissemination of knowledge gained during our project via the PI's co-directorship of the SCAR Scientific Research Program "Solid Earth Response and influence on Cryosphere Evolution" (SERCE). The SERCE program facilitates collaboration between Antarctic scientists around the world, and it sponsors the delivery of workshops and training schools relating to solid Earth - cryosphere interactions. Particular beneficiaries of this program (via targeted travel support) are early career researchers and researchers from countries that do not have their own polar programs.

No additional funds are needed to deliver these activities associated with academic impact.