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Using a new generation of radar satellites to monitor Earth's ice sheets

Dr Malcolm McMillan (SEE), Prof Andrew Shepherd (SEE)

Contact email: m.mcmillan@leeds.ac.uk

This project offers an exciting opportunity to work at the forefront of recent advances in satellite altimetry, with a focus on monitoring Earth’s Ice Sheets and global sea level rise.

The ice sheets of Greenland and Antarctica contribute approximately one third of global sea level rise, through ice melting and discharge into the oceans [Shepherd et al., 2012; McMillan et al., 2014a, 2016]. Projections indicate that, as Earth’s climate warms during the 21st Century, mass loss from the ice sheets will increase. However, determining the rate of acceleration remains extremely challenging, and represents one of the greatest uncertainties facing future sea level projections [Church et al., 2013].

To track the changes currently underway in the Polar regions, and improve confidence in future climate projections, requires detailed and systematic monitoring programmes. Given the vast and inaccessible nature of the ice sheets, this is only feasible from space. One technique that has proved particularly valuable in recent decades is that of satellite radar altimetry, which has been able to resolve the detailed pattern of mass loss across Greenland and Antarctica (Figure 1). This project will utilise recent developments in altimeter technology to develop state-of-the-art estimates of ice sheet change from new satellite missions.

Figure 1. Thinning of the Antarctic Ice Sheet between 2010 and 2013, observed using CryoSat-2 satellite altimetry.

In 2010, the European Space Agency (ESA) launched the CryoSat-2 satellite, marking a fundamental shift in satellite technology, and initiating a new era of high resolution, Synthetic Aperture Radar (SAR) altimetry. These novel data have transformed our ability to monitor Earth’s ice sheets, and to track their response to changes in climate [Helm et al., 2014; McMillan et al., 2014b, 2016]. Building upon these successes a new satellite, Sentinel-3, has recently been launched, which now offers an exciting opportunity to study ice sheet change, and to conduct research at the forefront of this emerging field.

This PhD project will establish the potential of Sentinel-3 SAR altimetry for monitoring current ice sheet change. As such, the successful applicant will have the opportunity to (1) work with state-of-the-art satellite data, (2) develop expertise in the most recent advances in instrument and processing techniques, and (3) address key questions in climate science, which hold global significance.

You will work as part of a team of Polar Earth Observation experts at the University of Leeds, and become a member of the UK national Centre for Polar Observation and Modelling. The project would suit a numerate candidate with a degree in a discipline such as Physics, Mathematics, Engineering, Earth Sciences, Computer Sciences or Geography.

Objectives

The aim of this project is to develop state of the art processing techniques for SAR altimetry, with a focus on observing ice sheet mass loss, and the associated contribution to sea level rise. The precise objectives will depend upon the successful candidate’s specific expertise and interests, but may include:

  1. Novel approaches to ice sheet elevation retrievals from SAR altimeter waveforms.
  2. Improving the certainty of SAR altimetry estimates of ice sheet mass loss.
  3. Mapping water loss from Antarctica’s subglacial lakes using a new era of high resolution SAR altimetry.

Figure 2. SAR altimetry may be used to map Antarctica’s subglacial lakes, such as the one sitting below this 70 m crater, which was recently identified in the ice sheet surface. The crater is thought to have formed when 6 billion tonnes of water drained from the underlying subglacial lake [McMillan et al., 2013]

Potential for high impact outcome

Understanding and monitoring current changes to Earth’s ice sheets is of global significance. Determining whether they are contributing or removing water from the oceans is important because these changes directly affect the global climate system, impacting upon present rates of sea level rise and many coastal communities. Understanding how ice sheets evolve is critical to developing realistic physical models of ice sheet evolution and reliable projections of future sea level rise. The potential of this project to deliver new insights into these processes is significant, given the novel datasets that will be utilized. This project provides the opportunity to be at the forefront of recent advances in SAR altimetry observation of ice sheets, and to deliver some of the first results using the new Sentinel-3 satellite. We therefore anticipate that the work will lead to several publications, with at least one submission to a high impact journal.

Training

The successful candidate will work under the supervision of Dr. Malcolm McMillan and Prof. Andrew Shepherd within the ICAS Polar Earth Observation group. The group, which currently includes 3 PhD students and 2 postdoctoral researchers, offers a supportive and collaborative environment for training as a polar Earth Observation scientist. The project will provide specialist training in geodetic Earth Observation techniques, algorithm development and data processing. The student will also benefit from being a member of the UK Centre for Polar Observation and Modelling (CPOM), a national research centre that brings together researchers from the universities of Leeds, UCL, Bristol and Reading, and has over twenty years of experience of satellite radar altimetry design, development and data processing. CPOM has close links to the European Space Agency (ESA) and the successful candidate will have the opportunity to participate in ESA workshops and meetings. There will also be access to a broad spectrum of training workshops put on by the Faculty, including computer programming, degree management and communication (http://www.emeskillstraining.leeds.ac.uk/).

References

Church, J. A. et al. (2013), Sea Level Change, in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. B. and P. M. M. (eds. ). Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, Cambridge University Press, Cambridge, UK.

Helm, V.,  a. Humbert, and H. Miller (2014), Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2, Cryosph., 8(4), 1539–1559, doi:10.5194/tc-8-1539-2014.

McMillan, M., H. Corr, A. Shepherd, A. Ridout, S. Laxon, and R. Cullen (2013), Three-dimensional mapping by CryoSat-2 of subglacial lake volume changes, Geophys. Res. Lett., 40(16), 4321–4327, doi:10.1002/grl.50689.

McMillan, M., A. Shepherd, A. Sundal, K. Briggs, A. Muir, A. Ridout, A. Hogg, and D. Wingham (2014a), Increased ice losses from Antarctica detected by CryoSat-2, Geophys. Res. Lett., 41, 1–7, doi:10.1002/2014GL060111.

McMillan, M. et al. (2014b), Rapid dynamic activation of a marine-based Arctic ice cap, Geophys. Res. Lett., 41, 8902–8909, doi:10.1002/2014GL062255.

McMillan, M. et al. (2016), A high-resolution record of Greenland mass balance, Geophys. Res. Lett., doi:10.1002/2016GL069666.

Shepherd, A. et al. (2012), A reconciled estimate of ice-sheet mass balance., Science, 338(6111), 1183–9, doi:10.1126/science.1228102.

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