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  • Author or Editor: G. Reverdin x
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G. Reverdin

Abstract

Surface temperature, salinity, and density are examined in the northeastern part of the North Atlantic subpolar gyre over the last 115 years of measurements. This region presents coherent variability in space but also between different seasons, with relatively small trends and large multidecadal variability. The most significant trend is a lowering in surface density. Multidecadal variability in T and S is large and is usually similar, with the largest difference between the two in the 1920s and a tendency of T to lead S. Multidecadal T and S are correlated with the winter North Atlantic Oscillation (NAO) index at 0 or 1-yr lag for T and 0 to 3-yr lag for S. This suggests a strong contribution of advection. The lag between T and S is also suggestive of a contribution of air–sea fluxes of heat or freshwater, but probably more so at high frequencies than at the multidecadal time scales. Salinity higher frequency is correlated with NAO at a 2–3-yr lag, whereas T higher frequency variability presents no correlation with NAO at any lag. This suggests different relations between seasonal NAO indices and air–sea heat fluxes patterns in this region before and after 1960; also the advective signal is more clearly identified in salinity in this region.

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J. W. Hurrell, M. Visbeck, A. Busalacchi, R. A. Clarke, T. L. Delworth, R. R. Dickson, W. E. Johns, K. P. Koltermann, Y. Kushnir, D. Marshall, C. Mauritzen, M. S. McCartney, A. Piola, C. Reason, G. Reverdin, F. Schott, R. Sutton, I. Wainer, and D. Wright

Abstract

Three interrelated climate phenomena are at the center of the Climate Variability and Predictability (CLIVAR) Atlantic research: tropical Atlantic variability (TAV), the North Atlantic Oscillation (NAO), and the Atlantic meridional overturning circulation (MOC). These phenomena produce a myriad of impacts on society and the environment on seasonal, interannual, and longer time scales through variability manifest as coherent fluctuations in ocean and land temperature, rainfall, and extreme events. Improved understanding of this variability is essential for assessing the likely range of future climate fluctuations and the extent to which they may be predictable, as well as understanding the potential impact of human-induced climate change. CLIVAR is addressing these issues through prioritized and integrated plans for short-term and sustained observations, basin-scale reanalysis, and modeling and theoretical investigations of the coupled Atlantic climate system and its links to remote regions. In this paper, a brief review of the state of understanding of Atlantic climate variability and achievements to date is provided. Considerable discussion is given to future challenges related to building and sustaining observing systems, developing synthesis strategies to support understanding and attribution of observed change, understanding sources of predictability, and developing prediction systems in order to meet the scientific objectives of the CLIVAR Atlantic program.

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