The nonlinear features of ocean mixed layer is investigated by the multifractal analysis on a thermistor chain data set collected in the Norwegian Current system in October 1989. The data set provides a two-dimensional temperature field from the surface to 250 m depth with 2 m resolution in vertical and 1.85 m resolution in horizontal, and shows high levels of variability excited over a large range of scales by the combined actions of external forcing and internal instability. The stationarity and intermittency are also discussed