TEMPORAL VARIATION OF MEANDERING INTENSITY AND DOMAIN-WIDE LATERAL OSCILLATIONS OF THE GULF-STREAM

The path of the Gulf Stream exhibits two modes of variability: wavelik e spatial meanders associated with instability processes and large-sca le lateral shifts of the path presumably due to atmospheric forcing. T he objectives of this study are to examine the temporal variation of t he intensity of spatial meandering in the stream, to characterize larg e-scale lateral oscillations in the stream's path, and to study the co rrelation between these two dynamically distinct modes of variability. The data used for this analysis are path displacements of the Gulf St ream between 75 degrees and 60 degrees W obtained from AVHRR-derived ( Advanced Very High Resolution Radiometer) infrared images for the peri od April 1982 through December 1989. Meandering intensity, measured by the spatial root-mean-square displacement of the stream path, display s a 9-month dominant periodicity which is persistent through the study period. The 9-month fluctuation in meandering intensity may be relate d to the interaction of Rossby waves with the stream. Interannual vari ation of meandering intensity is also found to be significant, with me andering being much more intense during 1985 than it was in 1987. Annu al variation, however, is weak and not well-defined. The spatially ave raged position of the stream, which reflects nonmeandering large-scale lateral oscillations of the stream path, is dominated by an annual cy cle. On average, the mean position is farthest north in November and f arthest south in April. The first empirical orthogonal function mode o f the space-time path displacements represents lateral oscillations th at are in-phase over the entire study domain. Interannual oscillations are also observed and are found to be weaker than the annual oscillat ion. The eigenvalue of the first mode indicates that about 21.5% of th e total space-time variability of the stream path can be attributed to domain-wide lateral oscillations. The correlation between meandering intensity and domain-wide lateral oscillations is very weak.