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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L02301, doi:10.1029/2003GL018584, 2004

Does the recent freshening trend in the North Atlantic indicate a weakening thermohaline circulation?

Peili Wu

Met Office, Hadley Centre for Climate Prediction and Research, United Kingdom


Richard Wood

Met Office, Hadley Centre for Climate Prediction and Research, United Kingdom


Peter Stott

Met Office, Hadley Centre for Climate Prediction and Research, United Kingdom


Abstract

It is widely expected that the thermohaline circulation of the ocean will slow down as greenhouse gas concentration in the atmosphere increases. This is partly due to an intensified hydrological cycle in a warmer climate. Is the recent observed freshening trend in the North Atlantic an indication of what has been expected? We report a similar freshening trend reproduced in an ensemble of four coupled model simulations with all major historical external (natural and anthropogenic) forcings. The modelled freshening trend originates from the Arctic Ocean where sea ice decrease and river runoffs increase with the same trend. Instead of weakening, we find an upward trend in the North Atlantic meridional overturning circulation.

Received 9 September 2003; accepted 3 December 2003; published 20 January 2004.

Index Terms: 4283 Oceanography: General: Water masses; 1635 Global Change: Oceans (4203); 1655 Global Change: Water cycles (1836); 1803 Hydrology: Anthropogenic effects; 4255 Oceanography: General: Numerical modeling.


Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 1335834 bytes)

Citation: Wu, P., R. Wood, and P. Stott (2004), Does the recent freshening trend in the North Atlantic indicate a weakening thermohaline circulation?, Geophys. Res. Lett., 31, L02301, doi:10.1029/2003GL018584.