Secondary circulation, referring to the motion relative to a basic flow (geostrophic and hydrostatic balanced), occurs often in the ocean such as deep convection and circulations driven by fronts and eddies. It affects the general circulation and the mass, heat, salt, and energy balance. The oceanic secondary circulation is difficult to measure directly, but is easy to be identified by pseudovorticity using routine observations. A C-vector method, commonly used in atmospheric mesoscale moist frontogenesis, is applied to oceanography for identifying frontal secondary circulation in Fram Strait using Conductivity-Temperature-Depth data collected during a large-scale hydrographic survey on R/V Valdivia cruise-54 of the eastern Greenland Sea and Fram Strait from 16 March to 5 April 1987. Possible application of this method to large-scale motion is also discussed.