Impacts of basin-scale forcing on the circulation of the Faroe Shetland Channel

MAST PhD Studentship at SAMS UHI.

Project Description: The Faroe Shetland Channel (FSC) is one of three regions within the North Atlantic where the warm waters from the sub-tropics flow northwards across the Greenland Scotland Ridge (GSR). This transfer of Atlantic water into the Nordic Seas is important for the regional climate of Scotland and, is also an important component of the Atlantic meridional overturning circulation (AMOC). Warm, northbound waters undergo transformation in the high latitudes and feed the southbound, dense water overflows across the GSR, forming the lower limb of the AMOC.

Since 1994, with the addition of profiling current meter moorings (Acoustic Doppler Current Profilers) to the already established hydrographic surveys, a sustained in situ monitoring system measuring the volume transport of Atlantic Water has been established. Recently, the integration of satellite altimetry data with these observations created a 20-year time series of Atlantic water volume transport through the FSC. Studies to date have mainly focused on establishing the mean volume transport of Atlantic Water and its seasonal cycle [Berx et al., 2013; Hughes et al., 2006].

This project will address the question: What are the circulation pathways from the sub polar gyre to the FSC and how are the local dynamics and variability in the FSC driven by basin-scale forcing? The project will analyse existing and new datasets in the FSC integrating the hydrographic observations, current meters, and altimetry; as well as link to additional datasets, such as the observations of the Argo array, providing information on the wider North Atlantic. As part of the project, there will be an opportunity to help with collecting data at sea, as part of the ongoing MSS monitoring programme in the FSC, which currently also forms part of the NACLIM (EU-FP7) project.
Furthermore, this project is an opportunity to use numerical model output as an estimate of the envelope of North Atlantic variability and to quantify, with error bars, which mechanisms contribute to transport variability in the FSC. A complete copy of 15 years of output from an eddy-resolving model is currently available at SAMS (Figure 2). This model has been used in previous studies of North Atlantic dynamics (Dr Gary) and exhibits a mean circulation (Figure 2) that is comparable to our understanding of observations (Figure 1).

The relationship between wind and buoyancy forcing and AMOC variability has been postulated for decades, but only now are there observations in place to explicitly verify this hypothesis. This project will leverage the oceanographic community’s growing observational network to search for links between basin-scale forcing and the variability of the upper limb of the AMOC. Ultimately, an understanding of AMOC variability is believed to be a key to predicting future climate since it is believed that the AMOC may play a significant role in many important climate processes (e.g. melting of sea ice and Greenland glaciers) as well as the regional climate of Scotland.

As for deliverables, we expect that the student will contribute to continuing the existing time series of volume, heat, and freshwater fluxes in the Faroe-Shetland Channel. Furthermore, the student will assess these fluxes in light of well-established climate indices (e.g. the North Atlantic Oscillation or the subpolar gyre index), extend these indices, and explore other measures of the basin-scale forcing. Finally, the student will use ocean model output to make an independent estimate for the uncertainty in the transports in the FSC. In addition to these deliverables, important outcomes from this project are that the student will collaborate closely with scientists from at least two institutions, work as part of a team to collect data at sea, and develop the skills to address the challenges of processing large datasets.

This project involves data collection in the field as part of a team of oceanographers which will augment existing observations. Computing transports in the FSC will require merging in situ historical and contemporary hydrographic observations, satellite observations, and modern current meter data. In the analysis stage, the student will employ, and evaluate, a variety of data reduction strategies (e.g. constructing climatological averages, empirical orthogonal functions, Lagrangian particle simulations) for both observations and model output.

Applicants should apply by submitting an application form, CV and referees comments to Fiona Wallace, Academic Registry Officer Postgraduate, The Scottish Association for Marine Science, Oban, Argyll, PA37 1QA or by email to [Email Address Removed]. Please visit SAMS website for application procedure http://www.sams.ac.uk/education/postgraduate

Closing date for applications is 31st October 2014.