[Opt-Net] PhD studentship opportunity

[Coralia Cartis]

NERC Industrial CASE Ph.D. Studentship in the Department of Earth Sciences and Mathematical Institute, University of Oxford

Title: Ocean Biogeochemical Optimisation in ESMs (OBOE)
 
Supervisors: Profs. Samar Khatiwala (Earth Sciences) and Coralia Cartis (Maths), University of Oxford; Prof. Colin Jones, NERC/Met Office; Drs. Andrew Yool and 
Adrian Martin, NOCS
 
Start date: October 2016
 
As one of the principal reservoirs of CO2, the ocean plays a crucial role in the carbon cycle and in regulating Earth's climate. Understanding and modelling 
the interconnections between the ocean carbon cycle and climate is therefore critical for robust estimates of future climate change. A principal challenge in 
this regard is the absence of well-established sets of equations governing the behavior of marine ecosystems, which play a key role in ocean carbon dynamics. 
Consequently, fundamental processes, such as the formation and sinking of organic matter from the surface into the ocean interior are crudely parameterised. 
Improving the representation of these processes in global ocean biogeochemical models, embedded within Earth System Models (ESMs) used to project future 
climate change, is thus an important goal of current research and of this project in particular. Specifically, we seek to evaluate and improve the performance of 
MEDUSA (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification), the ocean biogeochemical model in the next generation Met Office/
NERC Earth system model (UKESM), currently under development. MEDUSA models the interaction between macro- and micro-nutrients, phytoplankton and carbon, 
representing these processes through a range of parameterisations that include a number of key uncertain parameters. We seek to improve the underlying formulation 
of these parameters to better represent available observational constraints.
 
To achieve this a number of challenges need to be addressed. First, because of the complex interaction between biogeochemistry and circulation, model sensitivities 
vary both in space and time, as well as with respect to the model field (e.g., nutrients v primary production). Second, evaluating the performance of global 
models is prohibitively expensive as every parameter change requires integrating the model for several thousand simulated years to equilibrium before the model can 
be compared with observations. As a result there have been very few attempts at systematically optimising the performance of models such as MEDUSA. To overcome 
this, the student will exploit a fast "offline" tracer simulation scheme and recently-developed mathematical optimisation techniques to optimise MEDUSA, a first for a 
global biogeochemical model of this complexity, especially one used in a state-of-the-art ESM.
 
Key outcomes of this project include (1) an estimate of MEDUSA’s sensitivity to various parameters and thus the relative importance of key processes that affect the 
strength of the biological carbon pump; (2) an optimal set of parameters that minimizes the model-observation cost function built on several fields; and (3) a quantitative 
assessment of the impact of parameter optimisation on key aspects of UKESM1-projected Earth system change, such as global climate sensitivity, marine carbon uptake and 
the resulting biogeochemical state of the deep ocean.
 
This project brings together ocean biogeochemists, a mathematician and an Earth system modeller and the student will benefit from working actively with scientists from 
several disciplines, including the UKESM model development core group. S/he will receive training in not only marine biogeochemical and Earth system modelling, but 
also in high performance computing, numerical analysis and mathematical optimisation techniques with broad applicability in science and engineering. The student will 
be affiliated with Oxford's NERC-funded Environmental Science Doctoral Training Partnership (DTP) in Environmental Research and will thus benefit from courses offered 
through the DTP as well as the Mathematical Institute.
 
Eligibility: UK/EU students with a good (2.1 or higher, or its equivalent) first degree in the natural sciences, maths or engineering and strong computing skills are 
encouraged to apply.
 
Application process: To apply follow the instructions at http://www.earth.ox.ac.uk/graduate_admissions. Informal inquiries may be directed to: Samar Khatiwala 
(samar.khatiwala at earth.ox.ac.uk) or to Coralia Cartis (coralia.cartis at maths.ox.ac.uk).
 

-----------------------
Dr Coralia Cartis
Associate Professor in Numerical Optimization 
Mathematical Institute and Balliol College
University of Oxford

http://people.maths.ox.ac.uk/cartis