Effects of the New England Seamount Chain 

 on Gulf Stream Surface Flow 

 May 1979 



The relative levels of the pigment concentrations of the Gulf Stream 

 System have been described by Yentsch (Section 3, page 45) in terms of the 

 different water masses present, and the influence of tidal mixing in shallow 

 areas. In addition, the spatial patterns visible in the CZCS pigment images 

 are also of interest as tracers of the surface flow. 



The complex mesoscale eddy field in the water north of the Gulf Stream 

 is well-illustrated in the CZCS pigment image on 7 May (55-2). (Refer to 

 55-1 for geographical reference purposes.) Such spatial patterns can be 

 quantized in terms of their two-dimensional spatial spectrum (Gower 

 et al, 1981). Any variations in this spectrum, such as those suggested by 

 the increase in high frequency structure on the right side of the pigment 

 image, would be expected to correlate with the changing dynamics of 

 different ocean areas. Such a change is apparent between Area A to the 

 west and Area B to the east. The mean flow is from west to east at 

 0.5-1.0 m s"'. The chain of New England Seamounts (plotted as triangles) 

 crosses the image where this change in structure is observed. The 

 seamounts extend up from the bottom (5,000 m) to depths of between 

 1 ,000 and 2,000 m, and therefore intercept the Gulf Stream which flows in 

 the top 2,500 m of the ocean. Richardson (1981) has reported the effect of 

 these seamounts on the surface flow as traced by buoy tracks. He observed 

 meanders and small-scale (20 km) eddies, near and extending eastward 

 from individual seamounts. The CZCS pigment image illustrates this 

 effect more fully, with several instances of smaller eddies near the 

 seamounts, and a generally more disorganized flow to the east. 



The Gulf Stream is the major source of warm water for the North 

 Atlantic and has a strong influence on North American and European 

 climates, as well as on the Atlantic fisheries. New data on large-scale 

 distortion of the flow and the resulting mixing of the water, such as are 

 provided by CZCS pigment images, can make an important contribution 

 to our understanding of the global cHmate and food resources. 



References 



Gower, J. F. R., K. L. Denman, and R. J. Holyer, 1981: Phytoplankton patchiness 

 indicates the fluctuation spectrum of mesoscale turbulence. Nature, 288, 157-159. 



Richardson, P. L., 1981: Gulf Stream trajectories measured with free-drifting buoys. /. 

 Phys. Oceanogr.. 11, 999-1010. 



54 



