Interaction of the North Atlantic Current with the deep Charlie Gibbs Fracture Zone throughflow

The Charlie Gibbs Fracture Zone (CGFZ), a passage of 3600 sill depth throug h the Mid-Atlantic Ridge near 52 degrees N, is a known gateway for the pass age of deep waters from the Northeast Atlantic into the western basin. Duri ng a shipboard survey of August 1997 deep current profiling yielded eastwar d deep flow through the passage while geostrophy calculated against an inte rmediate reference level resulted in westward relative deep transport. The reason was an unusual and deep-reaching northward excursion of the North At lantic Current (NAC). Inspection of historical data showed that such interf erence of the NAC with the CGFZ regime occured occasionally in the past. Re location of surface circulation patterns by decadal ocean-climate anomalies may thus be of significance also for the deep circulation.