On the Influence of DSOW in a Numerical Model of the North Atlantic General Circulation

Abstract

Two numerical experiments regarding the North Atlantic circulation are compared. The two experiments are initialized with climatological temperatures and salinities and are integrated for ten years with different surface boundary conditions in the lceland Sea. One case climatological wind stress, SST, and surface salinity to force the model. It reproduces the Atlantic circulation found in similar studies. A change in surface boundary values In the Iceland Sea in order to improve the Denmark Strait Overflow water properties in the second case results in major changes in circulation and hydrography. The meridional overturning more than doubles and horizontal gyres are intensified. Recirculation cells occur north and south of the Gulf Stream. The Gulf Stream separates from the North American coast in a more realistic manner, and its further course is in better agreement with observations than in the reference run. The subsurface temperature distribution differs by several kelvin in the subpolar and subtropical gyres between the experiments. The authors examine mechanisms and timescales for the changes in the density field that result from the different buoyancy forcing and investigate how the large-scale circulation reacts. The adjustment takes place in two stages and is completed within a period of ten years. This result underlines the importance of variations in high-latitude buoyancy forcing for decadal variability in the Atlantic.