Numerous conductivity-temperature-depth data obtained in the Arctic basins are analyzed to describe structural features of intrusive layering. Special attention is paid to large intrusions (vertical scale of 40–100 m) observed in upper, intermediate and deep layers (depth ranges of 150–200, 200–600 and 600–1000 m, respectively). The analysis of the intrusions is accompanied by descriptions of the frontal zones where the layering was observed. Based on observations detailed estimates of frontal zone parameters are presented. Vertical profiles of temperature and salinity are found to have a well-defined “sawtooth” or “cog” shape, displaying a sequence of relatively thick, weak gradient layers, where temperature and salinity are decreasing with depth, interleaved with relatively thin, high-gradient sublayers, where temperature and salinity are increasing with depth. Some hypotheses about causes responsible for cog structure existence are discussed. Intrusions with high-amplitude anomalies in the vertical profiles of temperature and salinity are shown to be present at baroclinic fronts. Based on models of interleaving and data analysis the apparent vertical and lateral diffusivity in the frontal zones of the upper and deep ocean layers are estimated, and the slope of unstable modes relative to the isopycnals is examined at the baroclinic front in the situation when both temperature and salinity are stably stratified.