ON THE INFLUENCE OF DSOW IN A NUMERICAL-MODEL OF THE NORTH-ATLANTIC GENERAL-CIRCULATION

Two numerical experiments regarding the North Atlantic circulation are compared. The two experiments are initialized with climatological tem peratures and salinities and are integrated for ten years with differe nt surface boundary conditions in the Iceland Sea. One case uses clima tological wind stress, SST, and surface salinity to force the model. I t reproduces the Atlantic circulation found in similar studies. A chan ge in surface boundary values in the Iceland Sea in order to improve t he Denmark Strait overflow water properties in the second case results in major changes in circulation and hydrography. The meridional overt urning more than doubles and horizontal gyres are intensified. Recircu lation cells occur north and south of the Gulf Stream. The Gulf Stream separates from the North American coast in a more realistic manner, a nd 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 expe riments. 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 yea rs. This result underlines the importance of variations in high-latitu de buoyancy forcing for decadal variability in the Atlantic.