Back to the Future: Ice Sheet collapse, ocean circulation slowdown and abrupt climate change

Are you passionate about climate research and keen to tackle one of the greatest climate challenges of today? Are you keen to develop advanced research skills that can equip you for a wide range of future careers? For these reasons and more, you may be an ideal candidate to apply for a studentship with project VERIFY: Out Of Sample Testing For Early Warning Systems Using Past Climate.

For this PhD, you will perform state-of-the-art ice sheet and climate model simulations of Earth’s most recent ice sheet collapse and reorganisation of Atlantic Ocean circulation to test and improve forecasts of crossing tipping points in the Greenland ice sheet and North Atlantic Ocean in the future.

The fully funded scholarship is available in the School of Earth and Environment at the University of Leeds to begin in October 2025. The PhD is open to UK applicants and covers tuition fees and a maintenance stipend for three and a half years, as well as a Research Training Support Grant (RTSG) of £7,000 to fund research travel, training, conferences etc. The maintenance stipend is £20,780 in the year 2025/26.

Background

It is currently uncertain how the Greenland ice sheet will respond to current and future climate change, but we know that there were times in the past when the ice sheet, or parts of it, collapsed. Such an influx of cold, fresh water to the North Atlantic would be highly disruptive to the circulations that keep North American and European climates mild. Thus, we know that a collapse of the Greenland ice sheet would have dramatic consequences, globally, but exactly what those consequences are and when they might be triggered, is highly uncertain, with much disagreement among climate and ice sheet model projections.

The problem is that modern observations are too short and do not capture large enough changes to sufficiently test or calibrate the models, making it hard for decision makers to understand or act on the threat. The solution is to test models against the last known episode of major ice sheet collapse and reorganisation of Atlantic Ocean circulation, 8,200 years ago, when accelerated ice sheet melt in the Hudson Bay region disrupted the North Atlantic, inducing a century-long Northern Hemisphere cooling of several °C. Touted as the “Goldilock’s” event for benchmarking future North Atlantic change, this so-called ‘8.2 kyr event’ has quantified forcing and abundant palaeoclimatic (ancient climate) records for testing model responses.

This project aims to exploit the 8.2 kyr event to inform forecasts of future Greenland and North Atlantic ‘tipping’, performing new model simulations and merging the outputs with observational records using state-of-the-art techniques in artificial intelligence and machine learning.

The PhD

Using advanced uncertainty quantification, this project will combine complex climate and ice sheet models with geological records of Earth’s most recent ice sheet collapse and reorganisation of Atlantic Ocean circulation 8,200 years ago to provide ‘out of sample’ constraints on Earth System tipping, improving confidence in future climate projections.

Efficient experimental design will be used to expand the outputs from the UK Earth Systems Model (UKESM, a flagship complex model with interactive ice sheets) and drive ice sheet model simulations (BISICLES) of the 8.2 kyr event, varying uncertain model parameters and surface mass balance forcing. Advanced Gaussian process emulators (statistical models used in artificial intelligence/machine learning) will be applied to learn the relationships between uncertain model inputs and past/future ice sheet change. This will be used to optimally exploit information from models and real world data to better understand and project future tipping events in the Greenland ice sheet and North Atlantic Ocean. Implausibility metrics will rule out unrealistic models within uncertainty, producing a probability distribution of plausible ice sheet change, including meltwater forcing of North Atlantic Ocean circulation change.

These tools will be used to answer exciting research questions chosen by the postgraduate researcher with support from the project supervisors and wider VERIFY project team, for example:

• What were the mechanisms that controlled the Hudson Bay ice saddle collapse 8,200 years ago?
• How much meltwater did the event produce?
• What was the impact on the North Atlantic?

The PhD outputs will feed directly into other parts of Project VERIFY (e.g. a new early warning system for climate tipping) and the project may also investigate the usefulness of the 8.2 kyr event as a real-world ‘storyline’ to help decision-makers prevent or adapt to future climate change.

Project VERIFY

With this PhD Scholarship, you will be part of the Project VERIFY team, with access to a wide array of expertise and bespoke training. Our vision is to observe and understand massive changes (so-called tipping events) in the climate of the North Atlantic, namely the Greenland Ice Sheet and Subpolar Gyre, in the recent and geological past. Embedded in ten institutions internationally, Project VERIFY brings together experts in modern and palaeo-climate dynamics, high resolution and complexity modelling, data science and statistics, decision making and communication. The project will develop Digital Twins of these past events that will serve as a testbed for verifying whether this tipping behaviour can be predicted using Early Warning Systems (EWSs), forming a crucial component of a wider programme of effort to develop these systems in the North Atlantic region. In Project VERIFY, you will be part of a team of seven PhD students (plus postdocs and more senior researchers) working in a diverse array of disciplines, including social sciences, Earth System Modelling, ice and sediment core geochemistry, and dynamical systems and statistical analysis. You will also benefit from involvement in the broader research programme, which seeks to build an early warning system capable of providing the information, understanding and time we need to accelerate proactive climate adaptation and mitigation.