Abstract
Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of the \(z\)-coordinate overturning reveals model–data discrepancies: the vertical structure in the models does not change as much as the observed one. The East Greenland current variability is mainly wind-forced in the ATL6 model, while fluctuations due to eddies and instabilities explain a large part of the North Atlantic Current variability. The time-residual transport of dense water and heat due to eddy correlations between currents and properties is small across this section, which is normal to the direction of the main current.
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Acknowledgements
This paper is perhaps the last work that will bring together the main actors of the CLIPPER project (B. Barnier, G. Madec, J. M. Molines, T. Penduff, A. M. Treguier) and our thanks go to Christian Le Provost for initiating this successful modelling effort. Our collaboration will outlive CLIPPER, as we have now moved on to a new modelling project (DRAKKAR, Barnier et al. this issue). Our new project reinforces the collaboration between the French CLIPPER and German FLAME teams, which dates from the DYNAMO project in which Christian Le Provost also played a major part. One important aim of CLIPPER was to foster collaboration among modellers and “wet feet” oceanographers, and we hope that it is fulfilled in the present study. Members of the CLIPPER project team (as well as H. Mercier) are supported by CNRS and the computations have been made at the CNRS IDRIS computing center in Orsay. P. Lherminier is supported by IFREMER and C. Gourcuff by IFREMER and CNES. The FLAME model studies have been supported by the Deutsche Forschungsgemeinschaft through SFB 460; the computations were performed at the DKRZ, Hamburg.
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Treguier, A.M., Gourcuff, C., Lherminier, P. et al. Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model. Ocean Dynamics 56, 568–580 (2006). https://doi.org/10.1007/s10236-006-0069-y
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DOI: https://doi.org/10.1007/s10236-006-0069-y