Prof Peter Ashwin, Department of Mathematics, College of Engineering, Mathematics and Physical Sciences, University of Exeter
Prof Paul Valdes, School of Geographical Sciences, University of Bristol
Location: University of Exeter, Streatham Campus, Exeter, EX4 4QJ
This project is one of a number that are in competition for funding from the NERC GW4+ Doctoral Training Partnership (GW4+ DTP). The GW4+ DTP consists of the GW4 Alliance of research-intensive universities: the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus five unique and prestigious Research Organisation partners: British Antarctic Survey, British Geological Survey, Centre for Ecology & Hydrology, the Natural History Museum and Plymouth Marine Laboratory. The partnership aims to provide a broad training in the Earth, Environmental and Life sciences, designed to train tomorrow’s leaders in scientific research, business, technology and policy-making. For further details about the programme please see http://nercgw4plus.ac.uk/
For eligible successful applicants, the studentships comprises:
- A stipend for 3.5 years (currently £15,009 p.a. for 2019/20) in line with UK Research and Innovation rates
- Payment of university tuition fees;
- A research budget of £11,000 for an international conference, lab, field and research expenses;
- A training budget of £3,250 for specialist training courses and expenses.
- Travel and accommodation is covered for all compulsory DTP cohort events
- No course fees for courses run by the DTP
We are currently advertising projects for a total of 10 studentships at the University of Exeter.
As international efforts intensify to avoid dangerous climate change, it becomes increasingly important to develop pathways that minimise the risk of taking the climate system past a threshold or ’tipping point’ which triggers some effectively irreversible change. The Atlantic Ocean’s Meridional Overturning Circulation (AMOC) transports large amounts of heat from low latitudes into the North Atlantic, where it is given up to the atmosphere and plays a critical role in maintaining the relatively mild climate of western Europe. It is believed that in the past a collapse of the AMOC played a part in some extended cold periods seen in palaeoclimatic records. How would we know if the AMOC was approaching such a tipping point, and are there ’safe’ pathways towards an eventual target climate that minimise the chance of crossing one? These questions are the motivation for this PhD project.
Project Aims and Methods
Detailed earth system models are an essential tool to assess the climate, but their computational expense limits the scenarios that can be explored. The objective of this PhD is to explore a class of simpler, computationally cheap models  to provide insight into when the AMOC might pass a tipping point, and identify ways in which this could be avoided. The work builds on a recent study  that showed that tipping could occur for a variety of reasons; for example in some climate change scenarios the AMOC always remained stable in principle, but still if the climate change proceeded too fast the AMOC would collapse. Key questions for the project are: (a) showing that the simple model captures the essential dynamics of AMOC thresholds that are seen in GCM experiments and (b) using modern mathematical methods to analyse the dynamics of the AMOC thresholds in the simple model for various climate change pathways. The project will link simple models of future and past climate change to AMOC tipping models; it will then use rate-dependent tipping in dynamical systems to analyse circumstances under which tipping could occur, and possible climate stabilisation pathways that reduce the chance of tipping. This will suggest designs for additional GCM experiments to check predictions of the simple model.
References / Background reading list
 Wood, RA, Rodrigues, JM, Smith RS, Jackson LC, Hawkins E. 2019 Observable, low-order dynamical controls on thresholds of the Atlantic Meridional Overturning Circulation. Climate Dynamics (to appear)
 Alkhayuon H, Ashwin P, Jackson LC, Quinn C, Wood RA. 2019 Basin bifurcations, oscillatory instability and rate-induced thresholds for Atlantic meridional overturning circulation in a global oceanic box model. Proc. R. Soc. A 475: 20190051. http://dx.doi.org/10.1098/rspa.2019.0051