The Antarctic Intermediate Water in the North Atlantic Ocean is characterized by high concentrations of silica, and this characteristic is used to trace its circulation. An isopycnal map of silica reveals high-silica water extending on the west and north sides of the Mediterranean outflow water from the Straits of Florida as far northeast as 60N just south of Iceland. The extent of this high-silica Antarctic Intermediate Water is in remarkably good agreement with the path of the Gulf Stream-North Atlantic Current indicated by the geostrophic-flow field at this level.
Tsuchiya, Mizuki. 1989. "Circulation of the Antarctic Intermediate Water in the North Atlantic Ocean." Journal of Marine Research 47, (4). https://elischolar.library.yale.edu/journal_of_marine_research/1949