November 2016
Message 82

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

From Samar Khatiwala <>
Date Fri, 18 Nov 2016 09:40:02 +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, NERC/Met Office; Drs. Andrew 
and Adrian Martin, NOCS

Application deadline: January 20, 2017

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 
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 
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 
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 
engineering. The student will be affiliated with Oxford's NERC-funded 
Environmental Science Doctoral Training Partnership (DTP) in Environmental 
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 Informal 
inquiries may be directed to:  
Samar Khatiwala (

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