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Climate Dynamics

, Volume 34, Issue 7–8, pp 953–968 | Cite as

Seawater density variations in the North Atlantic and the Atlantic meridional overturning circulation

  • Chunzai WangEmail author
  • Shenfu Dong
  • Ernesto Munoz
Article

Abstract

Seawater property changes in the North Atlantic Ocean affect the Atlantic meridional overturning circulation (AMOC), which transports warm water northward from the upper ocean and contributes to the temperate climate of Europe, as well as influences climate globally. Previous observational studies have focused on salinity and freshwater variability in the sinking region of the North Atlantic, since it is believed that a freshening North Atlantic basin can slow down or halt the flow of the AMOC. Here we use available data to show the importance of how density patterns over the upper ocean of the North Atlantic affect the strength of the AMOC. For the long-term trend, the upper ocean of the subpolar North Atlantic is becoming cooler and fresher, whereas the subtropical North Atlantic is becoming warmer and saltier. On a multidecadal timescale, the upper ocean of the North Atlantic has generally been warmer and saltier since 1995. The heat and salt content in the subpolar North Atlantic lags that in the subtropical North Atlantic by about 8–9 years, suggesting a lower latitude origin for the temperature and salinity anomalies. Because of the opposite effects of temperature and salinity on density for both long-term trend and multidecadal timescales, these variations do not result in a density reduction in the subpolar North Atlantic for slowing down the AMOC. Indeed, the variations in the meridional density gradient between the subpolar and subtropical North Atlantic Ocean suggest that the AMOC has become stronger over the past five decades. These observed results are supported by and consistent with some oceanic reanalysis products.

Keywords

Atlantic Meridional Overturn Circulation North Atlantic Ocean Simple Ocean Data Assimilation Potential Density Atlantic Multidecadal Oscillation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

We thank reviewers’ suggestions and comments on this manuscript. We also thank Tim Boyer who provided us the updated salinity data before its public release. Gail Derr gave some editorial comments on an early version of the manuscript. This work was supported by a grant from National Oceanic and Atmospheric Administration (NOAA) Climate Program Office and by the base funding of NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML). The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the funding agency.

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.Physical Oceanography DivisionNOAA Atlantic Oceanographic and Meteorological LaboratoryMiamiUSA
  2. 2.Cooperative Institute for Marine and Atmospheric StudiesUniversity of MiamiMiamiUSA

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