Dr A Brearley, Prof A Naveira-Garabato, Dr D Smeed
No more applications being accepted
Competition Funded PhD Project (European/UK Students Only)
About the Project
Project Rationale :
Throughout the global ocean, regions of rough bottom topography are important locations of water mass mixing and transformation. Such processes commonly occur through the interaction of either mean or tidal flows with the topography, generating internal waves which subsequently break and dissipate their energy (e.g. Sheen et al., 2013). These processes assume an increased importance in the Southern Ocean where the modification of water masses can impact upper and lower limbs of the global ocean overturning circulation, with consequent impacts on global climate and the sequestration of heat and anthropogenic carbon.
A particular source of uncertainty in the transformation of water masses is in the north-south transfers of water between the Antarctic Circumpolar Current (ACC) – the globe’s largest current - and the gyre circulations that abut Antarctica. Recent work has suggested that transfers between the ACC and the Weddell Gyre, in the Atlantic sector, are mediated by dynamics associated with Taylor columns, which are features that circulate above peaks in the underlying seabed topography (Meredith et al., 2015), with large rates of stirring changing the properties of the ambient water masses. However, long term data sets documenting these processes have been limited, and measurements of the isopycnal (along density surface) and diapycnal (across density surface) transformation rates are sparse.
Methodology:
The student will work with float data, ship- and glider-based hydrography, and microstructure data collected as part of the ORCHESTRA project to:
1. Quantify rates of isopycnal stirring in the vicinity of a likely Taylor column located in the southern Scotia Sea, a key region of water mass exchange in the South Atlantic.
2. Quantify the dissipation rate of turbulent kinetic energy associated with the feature and identify the key periods of variability and processes controlling the diapyncal diffusivity.
3. Identify the signature of internal waves in the float data and uncover the dynamics which control the radiation and dissipation of internal wave energy. A recent study (Cusack et al., 2016) demonstrates the applicability of such techniques.
Later in the project, the student will use the understanding gained through the above objectives, along with numerical modelling and historical data sets, to identify other locations where such processes are likely to operate and to estimate a likely transformation rate for deep waters on a regional scale.
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 in Cambridge. Specific training will include:
You will be trained in various aspects of physical oceanographic data processing, including quality control, time series analysis, microstructure techniques and MATLAB. You will also have the opportunity to attend masters-level courses as appropriate, such as Large Scale Ocean Dynamics and Physical Oceanography. You will benefit greatly from interactions with the large number of PhD students, PDRAs and academic staff involved in physical oceanography both at BAS and within OES at the University of Southampton. The student may also have the opportunity to participate in ship-based fieldwork in the polar regions as part of BAS and NOC’s long-term science programmes in the Southern Ocean.
Funding Notes
You can apply for fully-funded studentships (stipend and fees) from INSPIRE if you:
Are a UK or EU national.
Have no restrictions on how long you can stay in the UK.
Have been 'ordinarily resident' in the UK for 3 years prior to the start of the project.
Please click link to http://inspire-dtp.ac.uk/how-apply for more information on eligibilty and how to apply
References
Cusack, J.M., A.C. Naveira Garabato, D.A. Smeed and J.B. Girton (2017), Observation of a large lee wave in the Drake Passage. J. Phys. Oceanogr., doi: 10.1175/JPO-D-16-0153.1.
Meredith, M. P., A. S. Meijers,
A. C. Naveira Garabato, P. J. Brown,
H. J. Venables, E. P. Abrahamsen,
L. Jullion, and M.-J. Messias (2015), Circulation, retention, and mixing of waters within the Weddell-Scotia Confluence, Southern Ocean: The role of stratified Taylor columns, J. Geophys. Res. Oceans, 120, 547–562, doi:10.1002/ 2014JC010462.
Sheen, K., J. A. Brearley, A. C. Naveira Garabato, D.A. Smeed, S. Waterman, J. R. Ledwell, M.P. Meredith, L. St. Laurent, A. M. Thurnherr (2013), Rates and mechanisms of turbulent dissipation and mixing in the Southern Ocean: Results from the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). J. Geophys. Res. Oceans, 118, 2774–2792, doi:https://doi.org/10.1002/jgrc.20217.