IAP-24-127

Laboratory modelling of internal tsunami generation due to ice calving

This project will consider the generation and behaviour of sub-surface waves, termed internal tsunamis which are generated by glacier calving events. Internal tsunamis propagate on density interfaces within a stably stratified water column where stratification is due to vertical variations in salinity and/or temperature. Recent observations by Meredith et al. 2022 have shown, for the first time, that glacier calving can be responsible for the generation of internal tsunamis which in turn play an important role in driving regional shelf mixing within the Southern Ocean. This has significant implications for glacier dynamics, ice shelf retreats, sea ice, and marine productivity, thus affecting global sea level and climate.

As global temperatures rise, calving events (and hence internal tsunamis) are predicted to become more widespread and more frequent, not just in Antarctica but anywhere where marine terminating glaciers exist (such as Alaska, Russia, Canada, Greenland, Patagonia, and Svalbard). Consequently, it is important that we gain a better understanding of the physics, fluid dynamics and associated marine and biological response to such events. To date, field studies are scarce and modelling efforts at a very formative stage.

In this project a laboratory-based approach is proposed to gain insight into how internal tsunamis are generated by calving events. The following questions will be investigated (i) how does internal tsunami generation depend on calving magnitude and type? (ii) how does the stratification influence the characteristics of the internal tsunami signature? and (iii) how do internal tsunamis mix the water column and dissipate their energy?

The results will inform how global ocean numerical climate models should be best parameterized to incorporate the effect of internal tsunami energetics.

Experiments will make use of a bespoke wave flume already installed at Newcastle University of dimensions 7m in length, 0.4m in width and 0.6m in height. The flume has been designed to study internal waves in stratified flows. The water column will be stratified using concentrated brine solution. Internal tsunami generation will be investigated via different generation techniques including vertical downward and upward release of weighted blocks of polystyrene. The shape, size, density, and surface roughness of the blocks will be varied along with the release height. In addition, the stratification profile will be varied to assess its role in this process.

Dynamics will be quantified using (i) time series analysis (ii) particle image velocimetry (PIV) (iii) synthetic schlieren and (iv) micro-conductivity sensors to measure the internal tsunami characteristics, the velocity field, the density field and vertical density profiles respectively. Attention will be restricted to 2D, to reduce the problem to a tractable size. These experiments will provide a detailed picture of how different calving types and magnitudes generate internal tsunamis and in turn how such events mix the water column.

The laboratory experiments will be compared with global ocean numerical simulations (that utilize MITgcm and NEMO) being performed by co-supervisors Munday and Inall. There will be scope to do numerical simulations that compare directly with the laboratory and to scale up the laboratory analysis to the field.

Year 1

Literature review.
PhD based skills training around data management, ethical research etc.
Training in laboratory techniques.
Experimental design and construction.

Year 2

Experiments on internal tsunami generation – focus will be on the generation method.
Comparing the experimental findings with numerical modelling (with support from co-supervisor Munday & collaborator Inall), and interpreting them in the context of relevant Antarctic and Arctic Ocean observations where possible (with support from co-supervisor Meredith and collaborator Inall).
Writing up of first data set.

Year 3

Experiments on internal tsunami measurements – focus will be on visualisation and associated flow measurements.
Comparison with numerical findings and scale analysis (with support from co-supervisor Munday & collaborator Inall).
Writing up of second data set

Year 3.5

Final analysis, writing and dissemination.

The PhD student will be trained to carry out experimental research using state-of-the-art measurement equipment. In addition, the student will learn how to efficiently collect, manage, and analyse large datasets. The student will also be trained to analyse and compare with results from numerical simulations to scale up experiments to the field-scale and explore the influence of parameter regimes on flow dynamics. The training will be broad and varied, sitting at the intersection of data driven and physics-based modelling. The student will be part of a strong, internationally-leading team working across three institutions (Newcastle, BAS and SAMS). The student will get exposure to international collaborators and the opportunity to become part of a global network. In addition, the team will consult regularly with the NERC funded POLOMINTS Large Grant team (led by co-supervisor Meredith). As such, the student will gain invaluable experience of working in a truly interdisciplinary team. In addition, there may be opportunities to gain experience and develop skills in polar fieldwork via the POLOMINTS field campaigns or other projects.
This project will position the student for a career in research, particularly fluid dynamics (mathematics, engineering, oceanography). In addition, careers requiring a candidate experienced with collecting, analysing, and handling large datasets able to work as part of an inter disciplinary team would be well suited.
This position is suitable for candidates who have/expect a first-class honours degree in mathematics, physics, physical oceanography, engineering or a closely related discipline. Candidates must demonstrate high academic potential to successfully complete the PhD project. Enthusiasm for research, an ability to think and work independently, excellent analytical skills and strong verbal and written communication skills are essential requirements. Some knowledge of fluid dynamics and an interest in experimental work are desirable.