Seasonal Variability Observed in the Gulf Stream East of Cape Hatteras

Abstract

The Gulf Stream system is dominated by strong mesoscale variability that can obscure any seasonal signals in Gulf Stream strength. Nevertheless, seasonal variability of the Gulf Stream is important for local weather and climate and can influence amplification of hurricane intensity and storm tracks. We investigate seasonal variability of the speed of the Gulf Stream after it detaches from Cape Hatteras, using high-resolution along-track altimeter data. The altimeter data show a significant seasonal cycle in the Gulf Stream axis speed, peaking in summer. The seasonal variability in the Gulf Stream axis velocity is related to changes in the local wind stress curl and changes in the density difference across the Gulf Stream. Wind forcing affects the Gulf Stream year-round, while changes in the density difference have the largest impact in summer. Overall, changes in the wind stress curl and upper ocean density difference across the Gulf Stream can explain roughly 40% of the seasonal Gulf Stream speed variability in summer.