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How does the Gulf Stream separate the Sargasso Sea from colder continental-slope waters?

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Map of the North Atlantic Ocean showing major ocean currents, with warm currents like the Gulf Stream and North Atlantic Drift highlighted in pink and cold currents in blue. Arrows indicate current directions and relative speeds, connecting the eastern coasts of North America, the western coasts of Europe and Africa, and the Arctic region. — Gulf Stream Major warm and cold currents of the North Atlantic Ocean.

The Gulf Stream acts as a major western boundary current that flows poleward, serving as a physical and dynamic barrier between two distinct water masses. It separates the warm, saline waters of the Sargasso Sea located to its east from the colder, slightly fresher continental-slope waters found to its north and west.1

This separation is maintained by the current's intense flow, which is driven by a horizontal pressure gradient force. The sea level across the Gulf Stream is approximately one metre higher on the side of the warm water lens than on the continental slope side, creating a geostrophic balance that sustains the current's path. While the Gulf Stream serves as this primary boundary, the interaction between these two regions is complex; meanders in the current can pinch off to form eddy structures, such as warm-core and cold-core rings, which transport heat and properties across the boundary between the Sargasso Sea and the continental-slope waters.1