Response of the overturning circulation to high-latitude fresh-water perturbations in the North Atlantic

PDF: http://data.dhkim.info/monograph/CD/Y08XU3VY8544V133.pdf

Article  

  Climate Dynamics
Publisher: Springer-Verlag Heidelberg
ISSN: 0930-7575 (Paper) 1432-0894 (Online)
DOI: 10.1007/s00382-003-0385-6
Issue: Volume 22, Number 4

Date:  April 2004
Pages: 359 - 372  
Response of the overturning circulation to high-latitude fresh-water perturbations in the North Atlantic
W. Cheng1  and P. B. Rhines1

(1)  School of Oceanography, University of Washington, Campus Box 355351, Seattle, WA 98195, USA

Received: 26 March 2003  Accepted: 20 November 2003  Published online: 27 February 2004

Abstract    Studies have suggested that sea-ice cover east and west of Greenland fluctuates out-of phase as a part of the Atlantic decadal climate variability, and greater changes are possible under global warming conditions. In this study, the response of the Atlantic meridional overturning circulation (MOC) to the distribution of surface fresh-water flux is explored using a global isopycnal ocean model. An Arctic ice related fresh-water flux of 0.1 Sv entering the Nordic Seas is shown to reduce the maximum overturning by 1 to 2 Sv (106 m3 s–1). A further decrease of 3 to 5 Sv in the MOC is observed when the fresh-water flux is shifted from the Fram Strait to the southern Baffin Bay area. Surprisingly, the salinity in much of the upper Nordic Seas actually increases when the Arctic fresh-water source is the strongest there, as a result of enhanced global overturning. It reflects the great influence of Labrador Sea convection on this models MOC. By applying a weaker surface fresh-water transport perturbation (0.02 Sv) on the Baffin Bay area and therefore perturbing the Labrador Sea Water (LSW) formation, we have also investigated the interaction between the overflows across the Greenland–Scotland Ridge and the LSW and find that, with the same surface forcing conditions in the Nordic Seas, volume transport of the overflows weakens when the LSW formation intensifies.