Using EN4 data-set from 1950 to 2015, the areas of the most intense deep convective mixing are identified as the maximum depths of the upper mixed layer during the cold season. It has been shown that the areas with the maximum registered convection depth of 1500-2000 m are found in the Greenland basin (73°-76° N, 5° W-1° E) and the Boreas basin (77° N, 1-2.5° W). This refines the areas of the deep convection derived from in situ data and results of hydrodynamic modeling. It has been shown that the previously separated in literature areas of deep convection in the Labrador Sea (55-59° N 50-56° W) and the Irminger Sea (57-60° N, 35-43° W), are in fact linked into one region by the episodic re-occurrence of the deep convection (1000 m and more) south of Greenland (between 56°-58° N). The intra-annual variability of deep convection was studied over the whole period of observations of 1950-2015. It is shown that the maximum depths of the upper mixed layer in all three seas was usually registered between December and May. The most often convection reaches the maximum depth in the Labrador and Irminger seas in March, and in the Greenland Sea - in April.