A Review of the Role of the Atlantic Meridional Overturning Circulation in Atlantic Multidecadal Variability and Associated Climate Impacts

Abstract

By synthesizing recent studies employing a wide range of approaches (modern observations, paleo reconstructions, and climate model simulations), this paper provides a comprehensive review of the linkage between multidecadal Atlantic Meridional Overturning Circulation (AMOC) variability and Atlantic Multidecadal Variability (AMV) and associated climate impacts. There is strong observational and modeling evidence that multidecadal AMOC variability is a crucial driver of the observed AMV and associated climate impacts and an important source of enhanced decadal predictability and prediction skill. The AMOC‐AMV linkage is consistent with observed key elements of AMV. Furthermore, this synthesis also points to a leading role of the AMOC in a range of AMV‐related climate phenomena having enormous societal and economic implications, for example, Intertropical Convergence Zone shifts; Sahel and Indian monsoons; Atlantic hurricanes; El Niño–Southern Oscillation; Pacific Decadal Variability; North Atlantic Oscillation; climate over Europe, North America, and Asia; Arctic sea ice and surface air temperature; and hemispheric‐scale surface temperature. Paleoclimate evidence indicates that a similar linkage between multidecadal AMOC variability and AMV and many associated climate impacts may also have existed in the preindustrial era, that AMV has enhanced multidecadal power significantly above a red noise background, and that AMV is not primarily driven by external forcing. The role of the AMOC in AMV and associated climate impacts has been underestimated in most state‐of‐the‐art climate models, posing significant challenges but also great opportunities for substantial future improvements in understanding and predicting AMV and associated climate impacts.

The role of Amazon river runoff on the multidecadal variability of the Atlantic ITCZ

“…The upperocean temperature shows mean warming in the North Atlantic without Amazon runoff, favoring a positive phase of AMV (figure 3(c)) whereas, with a doubling of Amazon runoff, the mean SST shows a cooling to the north (Supplementary figure 4(c)). But, the typical SST pattern associated with a positive AMV is a basin-wide warming in the North Atlantic and cooling to the south [10]. The tripolar SST pattern ( figure 3(c)) found in the North Atlantic Ocean is suggested to be induced by a negative NAO at interannual timescales [42] as proposed by [23].…”

“…On the other hand, when the Amazon runoff is doubled, the anomaly over the cold tongue becomes warmer and the meridional dipole reverses its sign (Supplementary figure 4(c)). Earlier studies suggest that the occurrence of meridional see-saw in SST anomaly over the tropical Atlantic Ocean is largely driven by the wind-evaporation-SST (WES) feedback in the tropical Atlantic Ocean [10]. However, in the absence of Amazon river input, the contribution of atmospheric feedback to the cooling in the southern tropical Atlantic Ocean in the 0AMZ is not significant (Supplementary figures 5(a) and (b)).…”

“…The fluctuations in large-scale meridional heat transport, the Atlantic meridional overturning circulation (AMOC), is a major source of global climate variability on decadal to multidecadal timescales [7,8]. The variability in AMOC-driven heat transport induces a basin-wide sea surface temperature (SST) anomaly termed as the Atlantic Multidecadal Variability (AMV [9,10]). The AMV is associated with the SST variability in the North Atlantic basin with alternate cold and warm phases occurring at a frequency of several decades.…”

Teleconnection Processes Linking the Intensity of the Atlantic Multidecadal Variability to the Climate Impacts over Europe in Boreal Winter

“…However, the added value of the initialization is considerably reduced over the North Atlantic adjacent continents, as found in most of CMIP5 decadal prediction systems (Goddard et al 2013, Doblas-Reyes et al 2013. Such a loss of predictability over land is somewhat paradoxical given the tight links that exist in observations between AMV and the decadal variations in summertime temperature and precipitation over the North American continent Hodson 2005, Ruprich-Robert et al 2017), over Europe Dong 2012, O'Reilly et al 2017) and over Africa for Sahel rainfall (Zhang and Delworth 2006). Note that greater predictive model performance is found for specific decadal shifts [e.g.…”

Sustainable Observations of the AMOC: Methodology and Technology

“…The AMOC transports heat, freshwater, carbon, and nutrients around the Atlantic. It is an important factor in decadal climate variations (Zhang et al, 2019), northern and southern hemisphere atmospheric patterns (Jackson et al, 2015;Lopez et al, 2016;McCarthy, Gleeson, et al, 2015) and to the rate of sequestration of anthropogenic carbon in the deep ocean (Steinfeldt et al, 2009). The convolutions of the Earth's geological past point to large, chaotic oscillations in the AMOC (Dansgaard et al, 1993).…”