Deep oceanic convection: A finescale view from marine robots

Rationale: 

Deep-water formation (convection) at high-latitudes, and more specifically in the Labrador Sea of the subpolar North Atlantic, affects the deep sequestration of carbon, nutrients, and heat. In a warming climate, a potential shutdown of the Meridional Overturning Circulation, which is essential to redistribute the oceanic excess of heat from low to high latitudes, is expected from the added volume of freshwater of Arctic and Greenland origins into the Labrador Sea. In the western Labrador Sea, water is exchanged between the Labrador Current and the basin interior due in part to small-scale (submesoscale <10 km) processes that alter convection and therefore modulate the deep storage of carbon. Due to the strong winds and high wave heights in the Labrador Sea, winter observations of small-scale features and of deep convective plumes at high-resolution are scarce. Therefore, the essential role played by submesoscale features in Labrador Sea convection remains poorly understood.

 

This project will use autonomous gliders to investigate how small-scale processes contribute to the shutdown of deep convection in the Labrador Sea. Such processes arise in deep narrow currents that flow over steep topography and in shallower waters affected by eddies and atmospheric (wind and buoyancy) forcing.

Methodology: 

The candidate will focus on two glider missions: one successfully completed over winter 2019/2020 and one forthcoming mission in winter 2021/2022. These missions will provide multiple high-resolution transects of temperature, salinity, velocity and turbulent mixing along and across the Labrador Current to characterise the presence of submesoscale instabilities and the associated lateral mixing, and to determine their role on the suppression of deep convection. These transects, which are located at various latitudes upstream and downstream of the convective region, will also inform on the evolution of the Labrador Current.

 

Additionally, the candidate may also use existing Argo float data that covers the top 2000 m of the water column, previous mooring deployments and ship-based hydrographic data to characterise interannual variability of water mass volumes over the western Labrador Sea. The multi-scale analysis of the ocean dynamics may be complemented by satellite altimetry and potentially by the future high-resolution ocean topography from the SWOT mission (Surface Water and Ocean Topography), planned for launch in 2022.

 

Location: 
NOC Southampton
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 in the Ocean Circulation and Processes Team at the National Oceanography Centre.

Specific training will include:

  • Possible opportunities to take part in fieldwork, which may include a large oceanographic research vessel or a glider deployment from small boats offshore of Greenland.
  • Training in numerical and statistical techniques with programming in Python.
  • Processing and analysis of glider data and various observational datasets.
  • Analysis of submesoscale physical processes.
  • Possible opportunities to take part in glider training e.g. at a summer school to learn about the deployment and processing of gliders and autonomous vehicles.
  • Opportunity to attend national/international conferences to disseminate the candidate’s results and to broaden their scientific network.

 

Eligibility & Funding Details: 

Please check https://inspire-dtp.ac.uk/how-apply for details.  

 

 

Background Reading: 
  • Thompson, A. F., Lazar, A., Buckingham, C., Naveira Garabato, A. C., Damerell, G. M., and Heywood, K. J., 2016: Open-ocean submesoscale motions: a full seasonal cycle of mixed layer instabilities from gliders. J. Phys. Oceanogr., 46, 1285—1307.
  • Cuny, J., Rhines, P. B., Schott, F. and J. Lazier, 2005: Convection above the Labrador continental slope. J. Phys. Oceanogr., 35, 489—511.
  • Naveira Garabato, A. C.., R. Ferrari, and K. L. Polzin, 2011: Eddy stirring in the Southern Ocean. J. Geophys. Res., 116, C09019.

 

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