Marine phytoplankton are key players in the global carbon cycle as they are responsible for half of the primary production (conversion of carbon dioxide and water into oxygen and organic carbon via photosynthesis) on Earth. The main controls on phytoplankton growth are light and nutrient availability.
Both observations and models have suggested that upper ocean mesoscale (eddies) and submesoscale processes (fronts) play an important role along with atmospheric forcing in regulating the availability of these resources and therefore phytoplankton community growth. Such processes, influence the vertical exchange between the water layers, regulating the light field and nutrient availability for the phytoplankton community at small spatial (metres to kms) and short temporal scales (daily to sub-daily), which are relevant for phytoplankton adaptation and acclimation.
Models with sufficient resolution to evaluate these processes are computationally expensive and most observation platforms (e.g. Argo floats) don’t sample and resolve the daily to sub-daily variability.
In this project, you will use high-resolution gliders to (1) understand and quantify the effect of small-scale and episodic physical processes on the phytoplankton community growth; (2) evaluate the importance of including small-scale processes in oceanic carbon uptake. Filling this knowledge gap using these high-resolution data will improve predictions of how the carbon uptake by phytoplankton is affected by both natural variability and changes in physical forcing driven by climate change.
Underwater gliders are autonomous robots that collect data continuously on ocean physics and biogeochemistry as they dive down to 1000m and back. Gliders resolve the bio-physical dynamics and its variability over a few hours to seasonal scales and at small horizontal scales. The project will initially use an existing 4-month glider deployment dataset to evaluate the upper ocean drivers of primary production, focusing on small scale forcing resulting from changes in water column structure. You will use glider-based estimates of spatial and temporal variability in turbulent mixing in the upper ocean, specifically distinguishing between seasonal mixed layer and actively mixing layer dynamics and relate these to glider chlorophyll-based estimates of phytoplankton growth.
Depending on your interests, subsequent work may include participation in an upcoming cruise, involving the deployment of 4 gliders and a drifting float in the Labrador Sea. You can then use the collected dataset to focus your analysis on the drivers of small-scale variability in upper ocean primary productivity.
Additionally, you may expand your analyses to a global comparison using a variety of high-resolution glider datasets in different biogeographical regions and evaluate the relative and global importance of small scale variability in different regions.
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 National Oceanography Centre (Southampton), in the Ocean Biogeosciences group. Specific training will include:
- Opportunities to take part in fieldwork, which may include large oceanographic research vessels and/or from small boats. You may have the opportunity to participate in the deployment of several gliders in the Labrador Sea.
- Opportunities to attend a hands-on glider training to learn about ocean gliders
- Training on processing and analysis of glider data and various observational datasets.
- The student may attend appropriate University and Masters level lectures to gain relevant background knowledge.
- Presentation of the results at (inter)national conferences will be encouraged to disseminate the candidate’s results and to broaden their scientific network.
Please see https://inspire-dtp.ac.uk/how-apply for details.
Hopkins, J. E., M. R. Palmer, A. J. Poulton, A. E. Hickman, and J. Sharples (2021), Control of a phytoplankton bloom by wind-driven vertical mixing and light availability, Limnol Oceanogr, 66(5), 1926-1949, doi:10.1002/lno.11734.
Carvalho, F., J. Kohut, M. J. Oliver, and O. Schofield (2017), Defining the ecologically relevant mixed‐layer depth for Antarctica's coastal seas, Geophysical Research Letters, 44(1), 338-345, doi:10.1002/2016gl071205.
Lévy, M., P. J. S. Franks, and K. S. Smith (2018), The role of submesoscale currents in structuring marine ecosystems, Nature Communications, 9(1), 4758, doi:10.1038/s41467-018-07059-3.
