Download AUGURY, Reconstructing Earth`s mantle convection

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AUGURY
Groundbreaking
geology
In an effort to accurately reconstruct the evolution of Earth’s mantle, Professor Nicolas
Coltice is collaborating with researchers across the globe, using data assimilation and
tectonic observations in a novel geological approach that will help inform a range of disciplines
Our results will give better constraints on the
paleogeography of the Earth, which is used
in a variety of disciplines from palaeontology
to mineral resource research. Reconstructing
the evolution of the Earth’s mantle and
surface tectonics together will allow sealevel reconstruction, which is fundamental
for water resource research, for instance.
Potentially, our models could provide a
better description of tectonics than plate
tectonics themselves.
Why have previous mantle convection
models been unable to describe how the
internal structure of the mantle impacts
surface tectonics and the dynamic feedback
between tectonics and convection?
Your work will create links between
convection models and tectonic data. Can
you summarise the context from which this
project emerged and its intended impact?
Plate tectonics allows geologists to
reconstruct the position of the continents
and evolution of the seafloor in Earth’s
‘recent’ past; however, it does not explain
the forces that drive this motion. In contrast,
mantle convection theory describes the
forces behind the motions within the rocky
mantle of the Earth, but fails to reproduce
the surface tectonics.
In collaboration with Professor Paul Tackley
at the Swiss Federal Institute of Technology
in Zurich and Tobias Rolf, a PhD student,
we have for the first time produced mantle
convection models that can make tectonic
predictions – thus, linking tectonics and
convection in a consistent manner is possible.
As with the climate sciences, we now have a
methodology to use both information from
observations and models to make predictions.
Instead of predicting what will happen in the
future (forecasting), we can predict what
happened in the past, during periods for which
we are lacking geological data.
Science progresses incrementally over time.
The concepts and much of the understanding
were already there, but the development
of computational power and methods was
fundamental. Most models were limited in
some way – Professor Paul Tackley created
a unique tool to partially resolve these
problems. After years of appreciating our
limitations, we may have given up on the idea
of producing a model of mantle convection
that could replace plate tectonic models.
Although we remain far from achieving
our goal, this new motivation is helping us
develop convection models that can tackle
the problem of connecting surface processes
to the deep Earth in a dynamic manner.
What methodologies will you use to
unfold coinciding theories of tectonic and
mantle evolution?
We will use data assimilation to connect Earth
tectonics and convection models. This method
aims to find the best compromise between
information using physics, a model, and
data that describe the system from another
point of view. Weather forecasting uses
such methodology, as does finance, climate
sciences, geomagnetism and other disciplines.
How important is collaboration to this
field of research? Can you discuss any
partnerships with external researchers
or laboratories in the course of
your investigations?
Collaboration is fundamental; we need
diverse fields of expertise to combine
models and data to make predictions about
the Earth. Geological and geophysical
observations require expertise in tectonics,
petrology, marine geophysics and
palaeomagnetism. Computer science is also
very important: building optimised software
for mantle convection and data assimilation
cannot be made without strong proficiency
in this field. We are working in collaboration
with Professor Tackley, an expert in
convection modelling, Professor Dietmar
Müller, a specialist in global tectonics at the
University of Sydney and Associate Professor
Alexandre Fournier, a pioneer in data
assimilation for geodynamics at the Paris
Institute of Earth Physics.
Can you outline the next steps to achieving
the project’s overall objectives?
I am working with several PhD students;
initially to estimate the time over which
models can be predictive – an issue on
which we have made great progress. We
are also developing a sequential data
assimilation method. Currently, we are
evaluating its ability to reconstruct the
deep structure from surface data. This
proof-of-concept step is important.
Moreover, evaluating the models in more
detail to see how they compare to the
theory of plate tectonics is also significant
to furthering our goals. It is essential to
know where further progress is required,
and where the models are efficient. Later
this year we will begin to develop advanced
data assimilation software, which should
become our ultimate tool when completed
in several years’ time.
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AUGURY
Model prediction of flow inside the Earth’s
mantle. Colours at the surface show
continents in blue and shearzones in red.
Interior colours correspond to temperature:
red represents high, and blue, low. Arrows at
the surface characterise velocities.
Modelling
Earth’s history
Knowledge of Earth’s palaeogeography is fundamental
to a number of sciences, but accurately modelling
the temporal dynamics of the planet has so far eluded
researchers. The Europe-wide AUGURY project is
developing innovative techniques to support this endeavour
MORE THAN 50 years ago the theory of plate
tectonics revolutionised understanding of the
Earth’s surface and its evolution, building on the
concept of continental drift to describe the largescale motion of the outermost shell of the Earth:
the crust and upper mantle. Tectonic motion is
caused by mantle convection, a process identified
30 years prior to plate tectonics, describing
currents that carry heat from deep inside the Earth
to the surface of the planet.
representations of mantle dynamics. Coltice made
a major breakthrough in a recent collaboration
with Professor Paul Tackley at the Swiss Federal
Institute of Technology (ETH) in Zurich, who has
dedicated the past 20 years to developing mantle
convection computational codes in spherical
geometry, and Tobias Rolf, a PhD student at ETH.
A geometry-based kinematic theory, plate
tectonics does not take into account the Earth’s
internal forces. Conversely, mantle convection
theory is more comprehensive, and modelling
offers the potential to provide imaging of past
and present mantle thermochemical structure.
However, in practice, convection models have
mostly failed to generate surface tectonics that
accurately reflect the Earth’s development, and
the shift from plate tectonics to mantle dynamics
is yet to be fully realised.
Coltice plans to build on recent
developments in order to
reconstruct plate tectonics and
convection history jointly
MAJOR BREAKTHROUGH
Professor Nicolas Coltice at the University of
Lyon, France, has played a key role in contributing
to new perspectives on how the Earth shaped
its surface environment billions of years ago,
through integrating geochemical and geophysical
A. Temperature field in a 2D convection model with selfconsistent plate generation (red is hot and blue is cold).
116INTERNATIONAL INNOVATION
For the first time, the researchers created mantle
convection models that successfully generate
surface tectonics comparable to the Earth,
predicting tectonic and convection evolution using
a single model. “There is still a long way to go, but
our first approach allows us to compare results
from first principles quantitatively with tectonic
models produced by geologists,” Coltice reflects.
While tectonic data are relatively restricted (it is
not possible to build accurate reconstructions past
B. Data assimilation (Kalman filter) of the temperature field
using surface velocities and surface heat flow from model A.
200 million years), using models enables the team
to compute billions of years of evolution. “We have
used models to estimate how surface tectonics
could behave over longer timescales than we can
observe today,” adds Coltice.
INNOVATIVE METHODOLOGIES
In his current project, Reconstructing Earth’s
Mantle Convection (AUGURY), on which Tackley
is also collaborating, Coltice plans to build on
these recent developments in order to reconstruct
plate tectonics and convection history jointly.
Using a multidisciplinary approach involving
geodynamics, tectonics, mathematics and
computer science, he is also collaborating with
Professor Dietmar Müller – a specialist in global
tectonics at the University of Sydney, Australia –
as well as a number of PhD and postdoc students.
The team aims to develop new methodologies
using information from tectonic datasets and the
physics of convection to produce a new generation
of tectonic and convection reconstructions. As
Coltice enthuses: “AUGURY will change not only
our perspective on the deep Earth, but will also
provide innovative tools and new information on
fundamental Earth science issues”.
The group plans to use data assimilation
strategies in conjunction with existing tectonic
data. This approach has never been used before
in geodynamics, although it is widely exploited
in disciplines such as meteorology, physical
oceanography and climatology. Data assimilation
combines information contained in numerical
models describing the dynamics of a system with
direct or indirect observations. Their methods will
enable kinematic models to be built using mantle
convection theory in place of plate tectonics.
Furthermore, the team has recently produced a
proof-of-concept tool using the Kalman filter – an
advanced sequential data assimilation method.
In parallel, Coltice also plans to develop a highperformance, sustainable, 4D variational data
assimilation (4D-Var) code that embeds the code
developed by Tackley – StagYY – and its adjoint
INTELLIGENCE
AUGURY
RECONSTRUCTING EARTH’S
MANTLE CONVECTION
OBJECTIVES
To reconstruct the history of the
movements of the solid Earth, from the
surface to the deep mantle.
PARTNERS
Université Claude Bernard Lyon 1, France
Ecole Normale Supérieure de Lyon, France
Plate tectonic reconstruction of the Earth 100 million years ago, provided by Professor Dietmar Müller’s Earthbyte group.
code. “This has more potential than the Kalman
filter approach: the formulation is more complete
and will allow hindcasting,” he explains. This part
of the project will require expertise in advanced
mathematical physics, as the adjoint code will need
Diagrams showing a model of plate tectonics with three
plates. Transform faults are in red and the rotation axis of
the relative motion between the blue and yellow plates
is demonstrated. Figure taken from teaching material at
geosciences3d.univ-lyon1.fr.
to be specially developed. The 4D-Var code will be
evaluated against synthetic and real data, and its
performance will be compared to the Kalman filter
methodology for cases with similar settings.
Centre National de Recherche
Scientifique, France
Institut Universitaire de France, France
Eidgenössische Technische Hochschule
Zürich, Switzerland
UNPARALLELED INSIGHT
University of Sydney, Australia
Dissemination of results is a major component
of AUGURY’s work. This will include publicising
data, developing teaching materials and creating a
digital hub accessible online for scientists, teachers
and the public. The hub will be designed to keep
track of the tools being developed as well as the
results generated, and will make the AUGURY
models publicly available in addition to statistical
descriptions of relevant convection solutions
obtained throughout the course of the project.
Those interested in the project’s findings will be
able to contribute to or use what the team creates,
and the shared data can be used to interpret
geophysical and geological data and models.
“Sharing our results with other research groups is
very important in order to respect what science is:
a humanist discipline,” adds Coltice. “I believe that
collaborating to solve problems can have a positive
impact in our discipline and beyond.”
FUNDING
AUGURY represents an innovative, transformative
step in the study of the solid Earth, and its findings
will impact a variety of geological disciplines. By
reconstructing the evolution of the 3D mantle
structure, Coltice and his team will be able to work
with seismologists and mineral physicists who need
information about the causes of seismic anomalies
in the deep Earth. “We will be able to tell them if
temperature alone is causing these anomalies, for
instance. This question is long-standing and we will
bring new perspectives to it,” Coltice reiterates. In
addition, elucidating the changing 3D structure of
the planet’s mantle will help scientists understand
the evolution of Earth’s geomagnetic field. Finally,
because the rotation of the planet is influenced by
mass redistribution within the mantle, Coltice’s
work could also contribute to elucidating further
constraints on this issue. “If all goes to plan, we will
finally reconstruct the deep Earth from geological
data, connecting the surface to the depths and
realise tectonic reconstruction in a more global
framework than plate tectonics,” he concludes.
“With geological data, we should be able to image
the deep Earth too, not just for the present day, but
also for ancient times. It is a new window to the
recent history of the solid Earth.”
www.augury.eu
The European Research Council within the
framework of the SP2-Ideas Program ERC2013-CoG
CONTACT
Professor Nicolas Coltice
Project Coordinator
Université Claude Bernard Lyon 1
Laboratory of Geology of Lyon
Batiment Geode
43 Boulevard du 11 Novembre 1918
69622 Villeurbanne Cedex
France
T +33 4 72 43 27 41
E [email protected]
NICOLAS COLTICE is a geodynamicist
whose research has focused on the solid
Earth. He is using modelling to bridge the
gap between observations and theories to
reconstruct the evolution of Earth from its
beginning to its recent geologic past. He
has also conducted educational projects at
national and European level.
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