Hydrographic surveys of the southern Canada Basin have been conducted in winter almost annually since 1979. Coverage has extended 100--200 km beyond the shelf to water depths of 2000--3000 m. Water properties in the upper 1500 m have fluctuated over intervals of a few years, and progressive changes have taken place during the 17 years of this study. At depths below the warm core of the Atlantic layer, water is warmer and fresher now than in the early 1980s. These changes reflect a thickening of the warm core at its lower boundary by more than 100 m. The maximum temperature of the Atlantic water has decreased by 0.06 ¿C, and the salinity at the maximum has decreased by 0.027. Above the Atlantic layer the lower halocline (34.5 isohaline) has cooled by 0.12 ¿C, a change which may indicate that ventilation of this level on the European side of the Arctic has been more effective in recent years. A good correlation between temperature fluctuations on the 34.5 isohaline and depth fluctuations of the lower 0 ¿C isotherm suggests common forcing of both parameters. Variation in the flow through the Barents Sea into the Arctic is proposed as that common influence. The upper halocine has warmed by 0.15 ¿C on the 33.5 isohaline. This trend could be a consequence of decreasing ventilation of the upper halocline over the broad shallow shelves on the Pacific side of the Arctic Ocean and may be related to the decrease in the strength of the Siberian High during the same time. The net result of changes in the hydrography of the Canada Basin has been an increase of 0.2 GJ m-2 in stored sensible heat, an amount sufficient to melt about 0.7 m of sea ice. The bulk of the increase results from the thickening of the Atlantic layer below 500 m. ¿ 1998 American Geophysical Union