The Distinction Between the Gulf Stream and Its North Wall

Abstract Downstream of Cape Hatteras, the Gulf Stream (GS) is bounded to the north by a sharp temperature front known as the North Wall (NW). Previous studies have generally assumed that variations of the NW and GS are equivalent. Using satellite sea surface height to identify the GS and the 15 °C isotherm at 200‐m depth to represent the NW, this paper examines their similarities and differences during 1993–2016. The NW and GS are geographically close and vary similarly only to the west of 71°W. Downstream of that, they rapidly diverge—and the variances of their latitudes increase by more than a factor of 2—as the GS flows past the New England Seamounts. Evidence is presented to show that the difference in properties of the NW and the GS is related to the presence of mesoscale eddies in the region separating them.