Letter | Published:

Ocean impact on decadal Atlantic climate variability revealed by sea-level observations

Nature volume 521, pages 508510 (28 May 2015) | Download Citation

Abstract

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 rainfall1, European summer precipitation2, Atlantic hurricanes3 and variations in global temperatures4. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content5. 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 source6. 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 region7. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining8 and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures4, 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 States9,10.

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Acknowledgements

G.D.M. and D.A.S. are supported by the UK Natural Environment Research Council (NERC) RAPID-WATCH programme. I.D.H. was partly supported by the UK NERC consortium project iGlass (NE/I009906/1). J.P.G. and J.J.-M.H. are supported by NERC National Capability funding.

Author information

Affiliations

  1. National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK

    • Gerard D. McCarthy
    • , Joël J.-M. Hirschi
    • , Jeremy P. Grist
    •  & David A. Smeed
  2. Ocean and Earth Science, National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK

    • Ivan D. Haigh

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Contributions

G.D.M. originated and developed the concept. I.D.H. provided the tide gauge data analysis. J.P.G. and J.J.-M.H. provided the numerical model analysis. D.A.S. carried out the statistical analysis. All authors contributed to the shaping and production of the manuscript

Corresponding author

Correspondence to Gerard D. McCarthy.

Comma-separated data used in the manuscript are available to download from http://bit.ly/1F7gtps.

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DOI

https://doi.org/10.1038/nature14491

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