The paper uses IGOSS data array as a basis to examine temperature of upper layer of the sea water in the knots of a regular grid for the period of 1982-2004 in one of the areas of the North European basin. Calculations of frequency structure of the long-term variations in data were performed and the main local energy carrying maxima in every knot of the regular grid in summer months were identified. Their spatial and seasonal instability were studied and the long-term prognosis for 2005 was made.