Challenging the limits of the AMOC’s latitudinal coherence

Dr Alejandra Sanchez-Franks, Dr Eleanor Frajka-Williams, Prof Harry Bryden, Dr Chris Banks
Rationale: 

The AMOC is a large-scale oceanic circulation comprised of currents that carry warm, shallow water northwards and return cold deep-water southwards. The AMOC impacts European temperature and precipitation variability and is crucial in maintaining the relatively mild winter climate of Northwest Europe.

 

Meridional coherence is the idea that changes observed in the AMOC at one latitude will also be observed at other latitudes. It is generally accepted that the AMOC is meridionally coherent on timescales longer than decadal. However on shorter timescales, it is not well understood where and how the meridional coherence of the AMOC breaks down, and how the associated driving mechanisms change [1]. This project aims to use for the first time a combination of in situ and satellite data to address these questions.

 

There is a current gap in our understanding of where the meridional coherence of the AMOC breaks down, what causes this, and what the implications are for the North Atlantic climate system. The primary objective of this project is thus to use new techniques combining in situ and satellite data to investigate these questions. This will lead to a better understanding of the influence of the North Atlantic on European climate.

 

Methodology: 

RAPID is an international campaign that has been monitoring the AMOC since 2004 using a moored instruments array along a line at 26ºN. Techniques have been recently developed using satellite-based altimetry and gravity measurements to estimate the AMOC strength at the RAPID line [2,3]. You will use the techniques developed at 26ºN to obtain direct estimates from satellite [2,3], providing a basis for extending the AMOC to the north and south of the RAPID line. This will enable you to reconstruct the first whole basin AMOC time series spanning 34ºS to 58ºN. Other mooring arrays such as MOVE (16ºN), OSNAP (58ºN) and SAMBA (34ºS) will provide validation for the satellite-derived estimates of the AMOC. For latitudes in between the mooring arrays, density profiles from Argo floats will be used to provide further validation for the satellite-derived AMOC estimates.

 

You will use the resulting latitudinal estimates of AMOC to investigate meridional coherence of the AMOC variability from annual to decadal time-scales. The overarching objective will be to assess the nature and evolution of the AMOC meridional coherence: where it holds, where it falls apart, its drivers and the wider implications these results have for the North Atlantic climate system.

 

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 at the National Oceanography Centre, Marine Physics and Ocean Climate group. Specific training will include:

-        You will be trained in analysis and interpretation of ocean observational data. You will be part of the RAPID team and have access to the expertise of a diverse and international group of scientists within the Marine Physics and Ocean Climate group.

-        You will get specific training in ocean observation techniques, which will include the opportunity to take part in a research expedition. More information on past and upcoming research expeditions led by the NOC listed here: https://noc.ac.uk/science/research-expeditions

You will be given training in communication skills, oral, written and presentation. The RAPID group has several international collaborators, and you will be encouraged to participate and present at national and international workshops and conferences

Eligibility & Funding Details: 

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

Background Reading: 

[1] Bingham, R. J.,  Hughes, C. W.,  Roussenov, V., and  Williams, R. G. (2007),  Meridional coherence of the North Atlantic meridional overturning circulation, Geophys. Res. Lett.,  34, L23606, doi:10.1029/2007GL031731.

[2] Sanchez-Franks, A., Frajka-Williams, E., Moat, B. I., and Smeed, D. A.: A dynamically based method for estimating the Atlantic meridional overturning circulation at 26° N from satellite altimetry, Ocean Sci., 17, 1321–1340, https://doi.org/10.5194/os-17-1321-2021 , 2021.

[3] Landerer, F. W., Wiese, D. N., Bentel, K., Boening, C., & Watkins, M. M. (2015). North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalies. Geophysical Research Letters42(19), 8114-8121

 

d96b37e25c18f40a