Seasonal variations in the Gulf Stream were analyzed using nearly 20 years of altimetry data from Topex, Jason-1, and Jason-2. Descending pass #50, which brackets the core of the Gulf Stream between 32-39°N and 68-72°W, was analyzed in terms of absolute sea surface height, referenced to a geoid model, and sea surface height anomalies, referenced to a global mean sea surface. Indices for geostrophic velocity, baroclinic transport, and average position of the Gulf Stream were also analyzed. The average annual distribution of the variables slowly increases throughout the year to late summer and early fall, quickly decreases to a minimum in winter, and increases to a secondary maximum in early spring. However, none of the seasonal time series resemble a pure sinusoid. The Gulf Stream behaves like a strongly nonlinear system. Peak values in near-surface geostrophic velocity occur in early summer, maximum northward migration of the Gulf Stream path in August, and maximum baroclinic transport in the fall. The seasonal variations in velocity are weaker than for the other parameters, which may be explained by the in-phase relationship between height changes across the current and the width of the current.
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