Using an ideal-fluid model, the main thermocline in the North Atlantic is reconstructed. The new feature in the model is the use of a nonlinear background stratification calculated from the hydrographic measurements collected on the Discovery cruise along 46–49°N. The basic stratification is assumed to be set up by an external thermohaline circulation and modified by a wind-driven circulation superimposed upon it. The numerical results of the model distinctly show the three-dimensional structure of the main thermocline in the ocean. In addition, the wind-driven gyre reaches a great depth (≈4.5 km), thus topographic effects on the gyre-scale circulation must be considered in further models. The model confirms the classical notion that the basic structure of the main thermocline and the three-dimensional density and velocity fields in the upper ocean can be simulated very well without explicitly including friction in the model.