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Southwest Indian Ocean currents: using new EO data and models to study changes and implications for global climate (part of the SENSE Centre for Doctoral Training’)

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  • Full or part time
    Prof M Srokosz
    Dr F Jebri
    Prof S Tett
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (UK Students Only)
    Competition Funded PhD Project (UK Students Only)

Project Description

The key hypothesis to be examined is that southwest Indian Ocean (SWIO) currents are changing and will continue to change into the future (possibly due to anthropogenic climate change). Specifically, are SWIO boundary currents, the Agulhas Current along the east coast of South Africa and the East Madagascar Current (EMC) along the east coast of Madagascar, changing and in what ways? This is important as the transport of warm salty water from SWIO into the Atlantic via the Agulhas Current is a major part of the global overturning circulation. Changes in this flow, and in the EMC which feeds the Agulhas, potentially affect the stability of the Atlantic meridional overturning circulation (AMOC) and eventually north western European and UK weather and climate. Under anthropogenic change western boundary currents, such as the Agulhas, are expected to alter. One view is that they will intensify but a recent work suggests that the Agulhas is broadening and not strengthening. Whichever is the case, the flow of the Agulhas (and so of warm salty water into the Atlantic) is determined by the upstream SWIO flows that feed it. Are these changing? If so, how?

The objectives that will allow that hypothesis to be addressed are:
1. Determine the flows and transports from the recent past (since the early 1990s) to the present.
2. Determine the flows and transports into the future (to the end of the century).
3. Examine the climatic implications of these changes.

Methodology:
The SWIO is one of the least well-observed, studied, understood and characterised regions of the world’s ocean. Therefore, this project brings together new satellite radar altimeter observations that allow currents that lie close to the coast to be determined (coastal and SAR altimetry), a new sea surface temperature dataset, a state-of-the-art high-resolution global ocean model, and coupled climate model projections of future change to examine recent past, present and future SWIO flows.

The satellite radar altimeter record now stretches back to the early 1990s and recent work has focused on obtaining more accurate measurements close to the coast, leading to the availability of new coastal altimetry data. In addition, the recent launch of the ESA Sentinel 3A and 3B satellites, that carry higher along-track resolution synthetic aperture radar (SAR) altimeters, also provides new opportunities for determining currents close to the coast. These new observations and datasets will be used to study the present and recent past (since the 1990s) changes in the Agulhas and East Madagascar current systems.

More than 35 years (1981-2016) of high-resolution satellite Sea Surface Temperature (SST) from the Climate Change Initiative (CCI) project will also be exploited to assess the changes. This product of multi-satellite (AVHHR, ATSRs and SLSTR) global SST data is specifically dedicated for climate and ocean model evaluation.

The new satellite observations will be compared to output from a high resolution (1/12˚) ocean model (NEMO) covering the altimeter observation period and used to validate coupled climate models from CMIP6 for the altimeter era. Those models that can reproduce the recent and present behaviour of the SWIO currents will then be used to determine the future behaviour of the current systems under anthropogenic climate change scenarios, and how these changes might affect the transport of warm salty water from the Indian into the South Atlantic Ocean and so global climate.

This PhD is part of the NERC and UK Space Agency funded Centre for Doctoral Training "SENSE": the Centre for Satellite Data in Environmental Science. SENSE will train 50 PhD students to tackle cross-disciplinary environmental problems by applying the latest data science techniques to satellite data. All our students will receive extensive training on satellite data and AI/Machine Learning, as well as attending a field course on drones, and residential courses hosted by the Satellite Applications Catapult (Harwell), and ESA (Rome). All students will experience extensive training on professional skills, including spending 3 months on an industry placement. See http://www.eo-cdt.org

Funding Notes

This 3 year 9 month long NERC SENSE CDT award will provide tuition fees (£4,500 for 2019/20), tax-free stipend at the UK research council rate (£15,009 for 2019/20), and a research training and support grant to support national and international conference travel. www.eo-cdt.org/apply-now

To be eligible you must:
1. be a UK or EU citizen, or a non-EU citizen with permanent settled status in the UK (known as ‘indefinite leave to remain’),
AND
2. have been ordinarily resident in the UK for at least 3 years prior to the start of the studentship (this applies to all citizen categories).

References

References for background
• Beal et al. 2011 On the role of the Agulhas system in ocean circulation and climate, Nature, 472:429-436
• Beal & Elipot 2016 Broadening not strengthening of the Agulhas Current since the early 1990s, Nature, 540:570–573, doi: 10.1038/nature19853
• Merchant, C.J.; Embury, O.; Bulgin, C.E.; Block, T.; Corlett, G.; Fiedler, E.; Good, S.A.; Mittaz, J.; Rayner, N.; Berry, N.A.; et al. (2019), Satellite-based time-series of sea-surface temperature since 1981 for climate applications. Nature Scientific Data, 6, doi:10.1038/s41597-019-0236-x
• Yang et al 2016 Intensification and poleward shift of subtropical western boundary currents in a warming climate, J Geophy Res, 121:4928-4945



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