January 2016
Message 6

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[Met-jobs] CASE Ph.D. Studentship in ocean biogeochemistry at the University of Oxford and Met Office

From Samar Khatiwala <>
Date Mon, 4 Jan 2016 20:33:36 +0000

NERC Industrial CASE Ph.D. Studentship in the Department of Earth Sciences and 
Mathematical Institute, University of Oxford; the UK Met Office; and National 
Oceanography Centre, Southampton

Title: Ocean Biogeochemical Optimisation in ESMs (OBOE)

Supervisors: Profs. Samar Khatiwala (Earth Sciences) and Coralia Cartis 
(Maths), University of Oxford; Prof. Colin Jones, Met Office; Drs. Andrew Yool 
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 
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 
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 
NERC Earth system model (UKESM), currently under development. MEDUSA models the 
interaction between macro- and micro-nutrients, phytoplankton and carbon, 
representing these processes via a range of parameterisations and associated 
parameters, which can have significant impact on key processes controlling 
uptake of atmospheric CO2. We seek to "tune" these parameters to better fit 

To achieve this a number of challenges need to be addressed. First, because of 
the complex interaction between biogeochemistry and circulation, model 
vary both globally as well as regionally, and also 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 projections of Earth 
system change such as climate sensitivity made by UKESM1.

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 
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 Informal inquiries may be 
directed to: Samar Khatiwala 

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