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A last millennium perspective on North Atlantic variability: exploiting synergies between models and proxy data

Ortega, P; Robson, J; Moffa-Sanchez, P; Thornalley, D; Swingedouw, D; (2017) A last millennium perspective on North Atlantic variability: exploiting synergies between models and proxy data. Past Global Changes Magazine , 25 (1) pp. 61-67. 10.22498/pages.25.1.61. Green open access

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Abstract

The North Atlantic is a key region for decadal prediction as it has experienced significant multi-decadal variability over the observed period. This variability, which is thought to be intrinsic to the region, can potentially modulate, either by amplifying or mitigating, the global warming signal from anthropogenic greenhouse emissions. For example, studies suggest that the North Atlantic contributed to the recent hiatus period between 1998 and 2012, by triggering an atmospheric response which impacted on the eastern tropical Pacific (e.g. McGregor et al., 2014). The subpolar North Atlantic is also a major CO2 sink, and therefore of great importance for the global carbon cycle (Perez et al., 2013). One of the key players in the North Atlantic region is the Atlantic Meridional Overturning Circulation (AMOC), which is associated with sinking due to deep water formation in the Labrador and Nordic Seas. The AMOC is the primary control of the poleward heat transport in the Atlantic region. Therefore, the AMOC is associated with important climate impacts, and plays an active role in various feedback mechanisms with, for example, sea ice (Mahajan et al., 2011) and the atmospheric circulation (Gastineau and Frankignoul, 2012). The AMOC has exhibited abrupt variations in the past (e.g. the last glacial period, Rahmstorf, 2002) and could experience a major slowdown in the future due to the combined effect of surface warming and Greenland ice sheet melting on deep water formation (Bakker et al., 2016). The possibility of such a shutdown has stimulated considerable international efforts to observe and reconstruct the past AMOC changes. Only by understanding its natural variability will we be able to detect and anticipate an anthropogenic impact on the AMOC. Decadal modulations are also found in other large-scale modes of climate variability, such as the North Atlantic Oscillation (NAO) (Stephenson et al., 2000), the Subpolar Gyre strength (SPG) (Häkkinen and Rhines, 2004) and the Atlantic Multidecadal Variability (AMV) (Enfield et al., 2001), which have all been linked with widespread climate impacts over the surrounding continents. Modelling studies suggest that all these modes interact with the AMOC (Gastineau and Frankignoul, 2012; Hátún et al., 2005; Knight et al., 2005) but the exact interrelationships are complex and remain to be disentangled. Also to be determined are the underlying mechanisms responsible for the decadal and centennial AMOC modulations, with different climate models showing different key drivers (Menary et al., 2015a). Similarly, the exact impact of the natural external forcings (e.g. volcanic aerosols, solar irradiance) on the variability of these different largescale climate modes still remains unclear.

Type: Article
Title: A last millennium perspective on North Atlantic variability: exploiting synergies between models and proxy data
Open access status: An open access version is available from UCL Discovery
DOI: 10.22498/pages.25.1.61
Publisher version: http://doi.org/10.22498/pages.25.1.61
Language: English
Additional information: Copyright © on any article is retained by the author(s). PAGES Magazine is distributed under the CC BY license which permits unrestricted use, distribution and reproduction in any medium, provided the article authors and all original sources are cited. For re-use of figures, we would like you to contact the author beforehand.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/1565282
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