IAPETUS
doctoral training partnership
Calibrating Glacial Isostatic Adjustment in Antarctica using
precise GPS rates
University of Glasgow, Geographical and Earth Sciences
In partnership with Newcastle University, Civil Engineering and
Geosciences
Supervisory Team
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Key Words
Dr Elizabeth Petrie, University of Glasgow.
http://www.gla.ac.uk/schools/ges/staff/elizabethpetrie/
Prof Peter Clarke, Newcastle University.
http://www.ncl.ac.uk/ceg/staff/profile/peter.clarke
Ingo Sasgen, GFZ German Research Centre for Geosciences,
Potsdam.
http://www.gfz-potsdam.de/en/staff-search/ingo-sasgen/
Precise GPS rates; Antarctica; vertical motion; loading; glacial
isostatic adjustment.
Overview
Accurate models of Antarctic glacial isostatic
adjustment (GIA) are needed when estimating ice
mass change i.e. the Antarctic contribution to sea
level. Using GPS to measure the motion of bedrock in
areas affected by GIA provides vital constraints on
GIA modelling. Antarctica is one of the most
challenging areas in the world to successfully collect
GPS data – the months of winter darkness, sparseness
of human activity, extreme winds and temperatures
and very limited rock exposure mean that data, while
highly useful, is very limited.
CAS1 site, East Antarctica
This project will test innovative strategies for
optimising processing of the sparse GPS data set and
establish a set of state of the art estimates of vertical
land motion in Antarctica. Creating meaningful trends
in Antarctica is particularly complex as the modern
ice loading history also affects rates. The study will
investigate the effects of local loading and
accumulation history in a test area on horizontal and
vertical trends from GPS. Finally, the impact of the
GPS trends on a GIA model will be established.
Methodology
The number of GPS sites being operated in Antarctica
has increased sharply in the last few years, and their
record lengths are becoming potentially viable as
robust indicators of vertical motion. However, the
available Antarctic dataset is highly variable in terms of
operator, equipment, collection purpose, and data
quality.
Unrecognised offsets in the time series are a major
source of error in the rate obtained from the GPS
time series. The project will investigate if
unrecognised antenna changes/types can be
successfully tested for, and also assess the effects of
snow cover on the antenna on the Antarctic GPS time
series. This will be done using Signal to Noise ratio
data (SNR). SNR data consist of measurements of
GPS signal power relative to a receiver-calculated
noise floor and are commonly reported by geodetic
quality GPS receivers and output to GPS format
RINEX files (Larson, 2013). These novel techniques
will be used to derive a cleaned Antarctic GPS
dataset.
GPS processing of the GPS data will be performed
using the GIPSY-OASIS scientific software, based on
state-of-the-art satellite orbit and clock data
processed at Newcastle. Trend and error estimation
methods developed at Glasgow/Newcastle will be
then applied to create a definitive Antarctic dataset of
vertical and horizontal rates.
Recent elastic loading effects in a test area will be
investigated using the SPOTL software. Finally,
forward-modelling of GIA in response to the past
evolution of the Antarctic ice sheet will be undertaken
and validated with the derived Antarctic uplift data
sets. A visit to Dr Sasgen at GFZ Potsdam, Germany,
to accomplish the tasks of GIA modelling is planned
for the third year. The visit is planned as one long trip
of ~2months, but could be adapted for students who
find may travel difficult due to personal commitments.
Timeline
Year 1: Review existing Antarctic GPS literature,
establish methods of testing for metadata errors and
snow deposits on antennas and learn to process data
in scientific GPS software.
Year 2: Write paper on testing results, present
results at conference. Collect and process all available
data using improved methodology. Create appropriate
reference frame for trends.
Year 3 – 3.5: Investigate local loading effects on
trends. Visit Dr Sasgen at GFZ Potsdam and
investigate the effects of updated trends on a GIA
model. Write paper on results, present at conference.
Complete thesis.
The above represents a broad overview of the
project. However, depending on the interests of the
student, there is the potential for the project to lean
more heavily towards the technical GPS/quality
checking side or the loading/GIA modelling side of the
project.
Training & Skills
During the course of the project, the student will gain
an understanding of GPS data and state of the art
precise GPS processing, crustal loading and
deformation, GIA modelling, global reference frames,
and time series/noise analysis. S/he will become
expert in least one scientific GPS processing package,
and develop skills in scripting, Matlab, the use of
version control and a GIA modelling package. There
will be the opportunity for the student to gain a
hands-on familiarity with GPS data collection.
Technical/paper writing skills and presentation skills
will also be developed. Conference attendance is likely
to be AGU or EGU once and a second
national/international conference.
Transferable skill development:
A full and progressive range of transferable skill
training is accessible to the student through IAPETUS
specific provision and the University of Glasgow, and
includes courses to stretch you in other ways e.g. 3D
printing in our Innovation platform; funding
applications.
References & Further Reading
King, M. A., et al. Improved constraints on models of
glacial isostatic adjustment: a review of the
contribution of ground-based geodetic observations.
Surveys in Geophysics, Springer, 2010, 31, 465-507
Herring, T. A. Geodetic applications of GPS.
Proceedings of the IEEE, IEEE, 1999, 87, 92-110.
Larson, K. M. A methodology to eliminate snow- and
ice-contaminated solutions from GPS coordinate time
series. J. Geophys. Res. Solid Earth, 2013, 118, 4503–
4510
Farrell W E and Clark J A 1976 On postglacial sea
level, Geophys. J. Int. 46 647–67.
Background on sea level change, GIA:
http://www.antarcticglaciers.org/2013/01/antarcticascontribution-to-global-sea-level-rise/
http://www.antarcticglaciers.org/glaciers-andclimate/sea-level-rise-2/recovering-from-an-ice-age/
Further Information
Contact details
Elizabeth Petrie: [email protected]