IAP-25-003

Changing freshwater inputs to the Southern Ocean due to rapid climatic change

The Southern Ocean plays a disproportionate role in global ocean circulation and the movement of heat, freshwater, carbon and nutrients around the planet. Ocean warming, changes in sea ice dynamics and winds, and melting of glaciers, ice shelves and ice sheets are changing the properties of the Southern Ocean. These physical changes are influencing the formation of deep and intermediate waters that drive the movement of water between the high and low latitudes, with knock on effects for biogeochemical cycling and biological production. There is a critical need to obtain a better understanding of the processes that drive freshwater input into the Southern Ocean, especially due to extreme events such as iceberg calving, large-scale glacier collapse or sudden retreats in sea ice extent. Only by understanding these links can we model future changes in freshwater inputs, and ocean circulation changes, associated with rapid climate change around Antarctica.

To do this, we need to be able to trace different types of freshwater inputs into the ocean through time and space. The different sources of freshwater inputs, from ice sheets, glaciers, and sea-ice, can be tracked using tracers such as the stable oxygen isotope composition of seawater (denoted by 18O) when coupled with salinity measurements. The aim of this research studentship is to bring together new and existing datasets of 18O, salinity, and other ancillary data from several recent expeditions to the Southern Ocean, with a focus on the Scotia and Weddell Sea. The student will have the opportunity to work with datasets, carry out laboratory work to make novel analytical measurements, as well as modelling to test hypotheses about changing freshwater inputs through time.

The candidate will be using a combination of new and existing datasets to calculate freshwater contributions to the Southern Ocean. Many of the existing datasets will be unpublished data collected during the BIOPOLE project cruises and via international project partners. New data will be generated at the British Geological Survey, and the candidate will have the opportunity to carry out a research placement to learn how the measurements are made. There will be opportunities to learn additional laboratory methods in BAS and BGS, if of interest, including other freshwater/oceanic tracers (e.g., barium, rare earth elements) and other biogeochemical parameters (e.g., nutrients, organic carbon). The freshwater calculations will be carried out using MATLAB or Python. The student will have the opportunity to investigate the representation of freshwater processes in existing numerical simulations, as well as to test specific hypotheses in novel simulations. There could also be opportunities to compare the results with Earth Observations (satellite data). There is no fieldwork required for this project, but there may be opportunities for the candidate to participate on an expedition to collect more samples.

Year 1

The candidate will carry out a literature review on the topic, and compile existing datasets together. They will begin calculations to partition the Southern Ocean freshwater budget into its relevant components, and start investigating the causes and consequences of variability in each. The candidate will learn how to use the modelling code and/or gain experience in using Earth Observation data.

Year 2

The candidate will carry out new measurements at BGS during a placement. They will continue to work on the modelling and processing of results. There will be opportunities to attend a national or international conference.

Year 3

The candidate will prepare manuscripts for submission for publication. There will be opportunities to attend a national or international conference.

Year 3.5

The candidate will continue to work on manuscripts and compile their thesis for submission.

The candidate will be trained in analytical chemistry, data management and processing, coding, modelling, and scientific writing and presentations. There may be the possibility to acquire fieldwork experience on a research cruise.