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Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society

COMMUNITY WHITE PAPER10.5270/OceanObs09.cwp.21

The Present and Future System for Measuring the Atlantic Meridional Overturning Circulation and Heat Transport

Stuart Cunningham(1), Molly Baringer(2), Bill Johns(3), John Toole(4), Svein Østerhus(5), Juergen Fisher(6), Alberto Piola(7), Elaine McDonagah(1), Susan Lozier(8), Uwe Send(9), Torsten Kanzow(6), Jochem Marotzke(10), Monika Rhein(11), Silvia Garzoli(2), Steve Rintoul(12), Bernadette Sloyan(12), Sabrina Speich(13), Lynne Talley(14), Johanna Baehr(15), Christopher Meinen(2), Anne-Marie Treguier(16), Pascal Lherminier(16)

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The Atlantic Ocean circulation redistributes up to 25% of the global combined atmosphere-ocean heat flux and so is important for the mean climate of the Atlantic sector of the Northern Hemisphere. This meridional heat flux is accomplished by both the Atlantic Meridional Overturning Circulation (AMOC) and by basin-wide horizontal gyre circulations. In the North Atlantic subtropical latitudes, the AMOC dominates the meridional heat flux, while in subpolar latitudes and in the subtropical South Atlantic the gyre circulations are also important. Climate models suggest the AMOC will slow over the coming decades as the earth warms, causing widespread cooling in the Northern hemisphere and additional sea-level rise. Monitoring systems for selected components of the AMOC have been in place in some areas for decades, nevertheless the present observational network provides only a partial view of the AMOC, and does not unambiguously resolve the full variability of the circulation. Additional observations, building on existing measurements, are required to more completely quantify the Atlantic meridional heat transport. A basin-wide monitoring array along 26.5°N has been continuously measuring the strength and vertical structure of the AMOC and meridional heat transport since March 31, 2004. The array has demonstrated its ability to observe the AMOC variability at that latitude and also a variety of surprising variability that will require substantially longer time series to understand fully. Here we propose monitoring the Atlantic meridional heat transport throughout the Atlantic at selected critical latitudes that have already been identified as regions of interest for the study of deep water formation and the strength of the subpolar gyre, transport variability of the Deep Western Boundary Current (DWBC) as well as the upper limb of the AMOC, and inter-ocean and intra-basin exchanges with the ultimate goal of determining regional and global controls for the AMOC in the North and South Atlantic Oceans. These new arrays will continuously measure the full depth, basin-wide or choke-point circulation and heat transport at a number of latitudes, to establish the dynamics and variability at each latitude and then their meridional connectivity. Modeling studies indicate that adaptations of the 26.5°N type of array may provide successful AMOC monitoring at other latitudes. However, further analysis and the development of new technologies will be needed to optimize cost effective systems for providing long term monitoring and data recovery at climate time scales. These arrays will provide benchmark observations of the AMOC that are fundamental for assimilation, initialization, and the verification of coupled hindcast/forecast climate models.

1National Oceanography Centre, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, United Kingdom
2Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, 4301 Rickenbacker Causeway, Miami, FL 33149, USA
3Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA
4Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA
5Bjerknes Centre for Climate Research and Geophysical Institute, University of Bergen, Allegata 70, N-5007 Bergen
6Leibniz Institut für Meereswissenschaften, Universität Kiel, Düsternbrooker Weg 20, D-24105 Kiel, Germany
7Servicio de Hidrografia Naval, Av Montes de Oca 2124, C1270ABV Ciudad Autonoma de Buenos Aires, Argentina
8Division of Earth and Ocean Sciences, Nicholas School Faculty, Duke University, 333 Old Chem, Box 90230, Durham, NC 27708-0230, USA
9Scripps Institution of Oceanography, UCSD (University of California, San Diego), 9500 Gilman Drive, San Diego, La Jolla, CA 92093-0225, USA
10Max Planck Institute for Meteorology, Bundesstraße 53, D-20146 Hamburg, Germany
11Institut für Umweltphysik, Universät Bremen, D-28359 Bremen, Germany
12The Commonwealth Scientific and Industrial Research Organisation, Locked Bag 10, Clayton South VIC 3169
13Université de Bretagne Occidentale, 3 rue des Archives, 292238 Brest Cedex 3, France
14Scripps Institution of Oceanography, UCSD (University of California, San Diego), 9500 Gilman Drive, San Diego, La Jolla, CA 92093-0230, USA
15Institute of Oceanography, KlimaCampus, University of Hamburg, Grindelberg 5, 20144 Hamburg, Germany
16Laboratoire de Physique des Océans, UMR (Unités Mixtes de Recherche) 6523 IFREMER-CNRS-UBO-IRD (French Research Institute for Exploration of the Sea/Institut Français de Recherche pour l'Exploitation de la Mer-Centre National de la Recherche Scientifique-University of Western Brittany-Institut de Recherches pour le Développement), BP 70, 29280 Plouzané, France,

Correspondence should be addressed to E-mail: stuart.cunningham@noc.ac.uk

This paper shall be cited as:

Cunningham, S. & Co-Authors (2010). "The Present and Future System for Measuring the Atlantic Meridional Overturning Circulation and Heat Transport" in Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society (Vol. 2), Venice, Italy, 21-25 September 2009, Hall, J., Harrison, D.E. & Stammer, D., Eds., ESA Publication WPP-306, doi:10.5270/OceanObs09.cwp.21

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