The role of Antarctic sea ice in glacial-interglacial climatic transitions

Project Rationale :
Since the onset of the Northern Hemisphere glaciation, Earth’s climate has undergone large transitions between cold “glacial” and warm “interglacial” stages. The paleoclimate record indicates that such transitions are associated with changes in atmospheric CO2 concentrations and ocean’s water masses distribution. Since the ocean is the largest carbon reservoir in the Earth system, processes affecting its ventilation can influence atmospheric CO2 and likely glacial-interglacial transitions themselves. However, we still lack a mechanistic understanding of how this feedback loop works, both in the past, present and future.
Antarctic sea-ice formation/export and circumpolar westerly winds represent a dominant part of the surface forcing of the Southern Ocean, driving the upwelling of the dense waters that fill most of the ocean interior and the formation of Antarctic Bottom Water, a key component of the global abyssal circulation. These processes would have varied substantially between glacial and interglacial climates and led to different large-scale circulation patterns; understanding such changes is key for future projections.
Southern Ocean dynamics are poorly represented in climate models [1] and observations in these regions are scarce. As a consequence, both modern and paleo data-model intercomparisons are characterized by large discrepancies [2,3]. Will this improve in the forthcoming CMIP6/PMIP4 simulations?

Methodology :
The student will analyse the output of CMIP6/PMIP4 models, to assess their performance in the Southern Ocean and how this differs between present and glacial climates. The focus will be on the link between sea ice and winds, and their influence on ocean circulation. A number of metrics and statistical tools will be applied for this purpose and model results will be evaluated against the instrumental and paleoclimate record.
The CMIP6/PMIP4 climate simulations will only be available starting in 2019 and contribute to the 6th assessment report of the Intergovernmental Panel for Climate Change (IPCC), which makes this analysis especially timely and of broad interest for the entire climate community. This will provide possibilities for high impact publications and several opportunities to attend and present results at international workshops and conferences.
The student will also gain experience in running both ocean-only and coupled ocean-atmosphere models, such as those used at the UK Met Office.
Numerical climate modelling is one of the most in-demand skills within international environmental research; this PhD will enable the student to develop those techniques, with the support of a team of supervisors with extensive expertise in ocean and climate modelling.

Training :
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the British Antarctic Survey.
Specific training will be provided through courses such as:

• NCAS Climate Model Support Workshop (Reading, UK)
• Unified Model (Met Office) training course (Exeter, UK)
• Urbino Summer School in Paleoclimatology (Urbino, Italy)
• PRACE Software Carpentry (UK)
• University of Cambridge/Southampton courses (e.g. Fluid Dynamics of Climate, Atmospheric Physics, Large Scale Ocean Processes)

At BAS and NOC you will have opportunities to participate in research cruises and fieldwork on the Antarctic ice sheets. There are possibilities for research visits in the US: University of Chicago, to work with external collaborator Prof. Malte Jansen, and Woods Hole Oceanographic Institution, through the UoS exchange programme.