CR2025_52 Modelling the Oceanic Cavities of the Antarctic Ice Sheet

Lead Supervisor: Ryan Patmore, National Oceanography Centre

Email: ryapat@noc.ac.uk

Co-supervisors: Jim Jordan, Department of Geography, Swansea University; Anthony Wise, National Oceanography Centre; Bernd Kulessa, Department of Geography, Swansea University

Antarctic Ice Sheet mass loss is one of the largest contributors to uncertainty in projections of future sea level rise. Floating sections of the ice sheet at the continental margines, termed ice shelves, act as an important interface between the ice and ocean. Marine driven melting within ice shelf cavities is the primary source of mass loss along many sections of the Antarctic Ice Sheet (Pritchard et al., 2012, Rignot 2013, 2019). Some of the greatest sources of uncertainty in projecting ice sheet mass loss stem from deficiencies in our representation of this melting. Difficulties with observing ice shelf cavities mean that modelling is a crucial source of understanding what cannot be directly observed. This project is aimed at finding the optimum methods for simulating both the marine driven melting and the import of warm water that feeds it. This will involve taking a fresh look at existing approaches for modelling ocean dynamics within ice shelf cavities, implementing emerging innovations in model coordinate systems and advancing the representation of ice shelf melting in global climate simulations.

Water depth in ocean models is typically divided into a number of layers, forming a vertical grid. A primary focus of this project is to improve the ocean model grid configuration within ice shelf cavities, with a particular interest in accurate representation of the physics at the sloping ice shelf-ocean interface. It has long been identified that existing grid representations illustrated by Fig. 1, which align with either the seabed topography (𝜎-coordinate) or gravity (z-coordinate), have limitations when it comes to realistically representing the physics at sloping boundaries (Gwyther et al., 2020). 𝜎-coordinates generate biases near steep transitions in water column thickness and z-coordinates have a stepped representation of topography that may generate spurious mixing.  Recent developments have seen the introduction of new gridding approaches that merge the 𝜎 and z representations and can dramatically improve results (e.g., Wise et al., 2023). These new approaches have yet to be implemented within ice shelf cavities, offering a unique opportunity to improve the representation of marine driven ice shelf melt. This project will investigate the benefits of these new coordinates within ice shelf cavities and identify the impact of implementation choices.

This exciting science programme will feed directly into the NOC global ocean modelling agenda, which is developing state-of-the-art modelling systems and contributing to leading international climate projections. The investigation will begin on a single ice shelf basis, starting with idealised experiments using the NEMO ocean model. The initial exploration will be followed by an opportunity to apply the new methods to more realistic settings such as the Bellingshausen or Amundsen seas of West Antarctica. There will also be scope to combine these methods in a coupled ice sheet-ocean system using the Úa model with which the second supervisor (Jordan) at Swansea University is intimately familiar. Configuring models of this complexity is a highly specialised role that requires significant investment of time and expertise. Following the NOC’s track-record in reproducible modelling (Polton et al., 2023), the candidate will have the opportunity to cement their standing in the field via the generation of open-source software tools for configuring model domains with the new approaches developed under this programme.

Training opportunities:

The candidate will have a variety of opportunities to develop skills and expertise in Oceanic and Cryospheric sciences and modelling, via:

• Attendance of direct training opportunities such as the Fluid Dynamics of Sustainability and the Environment Summer School hosted by Cambridge University, the Karthaus Glaciology Summer School, and NOC’s NEMO modelling workshop
• Elevating software development skills via integration in the NOC Marine Systems Modelling group where building skills are collectively encouraged via coding sprints and peer-to-peer support
• Participation and emersion in Swansea University’s Climate Action Research Institute 

Student profile:

This project would be suitable for students with a first degree in mathematics, physics, or a closely related environmental or physical science. Basic programming skills in languages such as Python, Matlab or R are desirable, but not essential for consideration.

Please note: Due to the nature of this project and to comply with visa regulations, only Home students should apply.