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Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall (1), European summer precipitation (2), Atlantic hurricanes (3) and variations in global temperatures (4). It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content (5). However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source (6). Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region (7). These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining (8) and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures (4), but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States (9,10)., The difficulty in linking ocean circulation changes to decadal climate variations lies in the fact that long observational records of ocean transports are rare. Measurements such as those of the [...]

The circulation system of the North Atlantic Ocean has weakened and is predicted to weaken further in the coming decades. An analysis suggests that this decline could lead to accelerated global surface warming.The circulation system of the North Atlantic Ocean has weakened and is predicted to weaken further in the coming decades. An analysis suggests that this decline could lead to accelerated global surface warming., Author(s): Gerard D. McCarthy, Peter W. ThorneAuthor Affiliations:Sluggish Atlantic circulation could cause global temperatures to surge The connection between the AMOC and variations in the heat content of the subpolar [...]